Solid electrolyte and preparation method and application thereof

Abstract

The invention provides a solid electrolyte and a preparation method and application thereof, the chemical composition of the solid electrolyte is LixGayAaDbOc, 0.5 < = x < = 2.0, 0.1 < = y < = 0.5, 0.1 < = a < = 1, 3.5 < = b < = 5, 0.25 < = c < = 1.5; a comprises four or more of Y, In, Al, La, Ce, Ho, Zr, Ta and Nb, and D comprises one or more of F, Cl and Br; in an X-ray diffraction pattern, diffraction peaks of 2 theta at 24 degrees to 26 degrees, 27 degrees to 29 degrees, 42 degrees to 46 degrees and 49 degrees to 54 degrees are included. According to the solid electrolyte provided by the invention, by limiting the chemical composition and the diffraction peak 2 theta in XRD, the disorder degree of the solid electrolyte can be improved, the ionic conductivity can be improved, and the flexibility of the solid electrolyte can also be improved, so that the specific capacity and the cycle performance of the battery are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a solid electrolyte and a preparation method and application thereof. Background Art

[0002] Solid-state batteries have the advantages of high energy density and strong safety, and are regarded as favorable competitors for the next generation of lithium batteries. The core component of solid-state batteries is solid electrolytes, which also serve as lithium ion transport and diaphragms. Currently, commonly used solid electrolytes are divided into organic solid electrolytes and inorganic solid electrolytes. Due to the low ion conductivity of organic solid electrolytes, it is difficult to meet the needs of high energy density batteries. The emerging inorganic halide solid electrolytes have the advantages of wide electrochemical window and good processability and are gradually becoming one of the mainstream electrolytes.

[0003] However, the inorganic solid electrolytes in the prior art still have the problems of low ion conductivity and poor solid-solid interface contact with the electrode materials, which leads to low specific capacity of the battery and poor cycle performance. Summary of the invention

[0004] The main purpose of the present invention is to provide a solid electrolyte with high ionic conductivity and good solid-solid interface contact with electrode materials. When applied to batteries, the specific capacity and cycle performance of the batteries can be improved.

[0005] The present invention also provides a method for preparing a solid electrolyte, which can prepare the above-mentioned solid electrolyte and has simple process and low cost.

[0006] The present invention also provides a positive electrode sheet, comprising the above-mentioned solid electrolyte, so that the positive electrode sheet is applied to a battery to improve the specific capacity and cycle performance of the battery.

[0007] The present invention also provides a battery, comprising the solid electrolyte, so the battery has excellent specific capacity and cycle performance.

[0008] In a first aspect, the present invention provides a solid electrolyte, wherein the chemical composition of the solid electrolyte is Li x Ga y A a D b O c , wherein 0.5≤x≤2.0, 0.1≤y≤0.5, 0.1≤a≤1, 3.5≤b≤5, 0.25≤c≤1.5; A includes four or more of Y, In, Al, La, Ce, Ho, Zr, Ta, and Nb, and D includes one or more of F, Cl, and Br;

[0009] The X-ray diffraction pattern includes diffraction peaks at 2θ located at 24°-26°, 27°-29°, 42°-46° and 49°-54°.

[0010] In the solid electrolyte as described above, the A includes the Y element, and the molar ratio of the Y element to the Ga element is 1:(0.45-1.5).

[0011] In the solid electrolyte as described above, D includes two or more of F, Cl and Br.

[0012] In the solid electrolyte as described above, the D at least includes F.

[0013] In the solid electrolyte as described above, the molar ratio of any one of the metal elements in A to Ga is (0.8-1.2):1.

[0014] The solid electrolyte as described above is in the form of clay.

[0015] The solid electrolyte as described above, wherein the ionic conductivity of the solid electrolyte is greater than 1 mS / cm.

[0016] For the solid electrolyte as described above, in the X-ray diffraction spectrum, the half-width of the widest diffraction peak is greater than or equal to 1.35°.

[0017] The solid electrolyte as described above, wherein the Young's modulus of the solid electrolyte is less than or equal to 3 GPa.

[0018] In a second aspect, the present invention provides a method for preparing the solid electrolyte as described above, comprising the following steps:

[0019] 1) grinding a raw material system including lithium halide, lithium oxide, gallium halide, and a halide containing element A to obtain a mixture;

[0020] 2) Under an inert atmosphere, the mixture is subjected to ball milling treatment and heat treatment in sequence to obtain the solid electrolyte.

[0021] The preparation method of the solid electrolyte as described above, wherein the grinding treatment time is 5 min-30 min;

[0022] And / or, the rotation speed of the ball milling treatment is 400rpm-600rpm, the time is 0.5h-4h, and the ball-to-material ratio is (10-40):1;

[0023] And / or, the heat treatment temperature is 150°C-250°C, and the time is 1h-4h;

[0024] And / or, the halide containing element A includes yttrium halide, and the molar ratio of the yttrium halide to the gallium halide is 1:(0.45-1.5).

[0025] In a third aspect, the present invention provides a positive electrode sheet, comprising the solid electrolyte as described above or a solid electrolyte prepared by the method for preparing the solid electrolyte as described above.

[0026] In a fourth aspect, the present invention provides a battery, comprising the solid electrolyte as described above, or a solid electrolyte prepared by the method for preparing the solid electrolyte as described above, or a positive electrode sheet as described above.

[0027] The solid electrolyte provided by the present invention can improve the disorder degree of the solid electrolyte, improve the ionic conductivity, and increase the flexibility of the solid electrolyte by limiting the chemical composition and the diffraction peak 2θ in XRD, so that the solid electrolyte can form a stable interface layer when in contact with the electrode material, reducing the generation of interface reaction and by-products. This good interface contact is conducive to the effective transmission of ions, thereby improving the specific capacity and cycle performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present invention or related technologies. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 The XRD diagrams of the solid electrolytes of Example 1 and Comparative Example 1 of the present invention;

[0030] Figure 2 is the XRD diagram of the solid electrolyte of Example 2 of the present invention;

[0031] Figure 3 is the XRD diagram of the solid electrolyte of Example 3 of the present invention;

[0032] Figure 4 is the XRD diagram of the solid electrolyte of Comparative Example 2 of the present invention;

[0033] Figure 5 is the XRD diagram of the solid electrolyte of Comparative Example 3 of the present invention;

[0034] Figure 6 is the XRD diagram of the solid electrolyte of Comparative Example 4 of the present invention;

[0035] Figure 7 is the XRD diagram of the solid electrolyte of Comparative Example 5 of the present invention;

[0036] Figure 8 a is the morphology of the solid electrolyte of Example 1 of the present invention, and b is the morphology of the solid electrolyte of Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Solid-state batteries are at the forefront of next-generation lithium battery technology, and their core lies in the performance optimization of solid-state electrolytes. Solid-state electrolytes not only need to act as a medium for lithium ion transmission in the battery, but also need to have the function of a diaphragm to ensure the safety and stability of the battery. Although traditional liquid electrolytes have high ionic conductivity, their flammability and leakage risks limit their application in high-energy density batteries. In contrast, solid-state electrolytes have become a hot topic of research due to their non-flammability and high temperature resistance.

[0039] In the classification of solid electrolytes, inorganic solid electrolytes, especially inorganic halide solid electrolytes, have gradually attracted attention due to their wide electrochemical window and excellent processability. However, existing inorganic solid electrolytes still face some technical challenges. First, their ionic conductivity is relatively low, which makes it difficult to meet the needs of high power density applications. Secondly, the inorganic halide solid electrolytes themselves have certain mechanical properties. During the assembly process of solid-state batteries, the solid-solid interface contact between the solid electrolyte and the electrode material is poor, resulting in increased interface impedance. This interface problem not only limits the effective transmission of lithium ions, but also affects the specific capacity and cycle performance of the battery. Therefore, how to improve the ionic conductivity of inorganic solid electrolytes and improve their interface contact with electrode materials has become a key bottleneck in the current technological development.

[0040] The inventors of the present application have found through research that if the structure-activity relationship of the material itself can be improved to a certain extent, while softening the material, a relatively high ionic conductivity can still be maintained, which will greatly reduce the performance degradation of the battery caused by interface problems.

[0041] Based on this, in the first aspect, the present invention provides a solid electrolyte, the chemical composition of the solid electrolyte is Li x Ga y A a D b O c, wherein 0.5≤x≤2.0, 0.1≤y≤0.5, 0.1≤a≤1, 3.5≤b≤5, 0.25≤c≤1.5; A includes four or more of Y, In, Al, La, Ce, Ho, Zr, Ta, and Nb, and D includes one or more of F, Cl, and Br; in the X-ray diffraction pattern, the diffraction peaks of 2θ are located at 24°-26°, 27°-29°, 42°-46°, and 49°-54°.

[0042] For example, x can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 or a range consisting of any two thereof; y can be 0.1, 0.2, 0.3, 0.4, 0.5 or a range consisting of any two thereof; a can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 Or a range consisting of any two of them; b can be 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5 or a range consisting of any two of them; c can be 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or a range consisting of any two of them.

[0043] The solid electrolyte provided by the present invention has high ionic conductivity and good solid-solid interface contact with the electrode material. It is applied to the battery to improve the specific capacity and cycle performance of the battery. The reason is that the content of Li can provide sufficient lithium ion concentration, which helps to improve the ionic conductivity. A includes at least four metal elements, that is, the solid electrolyte includes at least five metal elements, which is a high-entropy halide solid electrolyte. The high entropy effect can lead to an increase in disorder in the lattice, thereby creating more migration channels and defects, which helps to improve the mobility and overall ionic conductivity of lithium ions. In addition, the D element includes one or more of F, Cl and Br, and the Ga element has a synergistic effect with the monovalent halogen anion. When the two coexist, by changing the crystal structure type, the amorphous proportion of the solid electrolyte is significantly increased, thereby increasing the flexibility of the solid electrolyte, changing its physical characteristics, and changing from powder to clay. Oxygen ions are divalent anions, which are completely different from the halogen anion structure. The disorder of the structure is enhanced by introducing heterovalent elements at the anion end, which increases the defect sites and carrier concentration in the crystal structure, and significantly improves the lithium ion conductivity. While improving the flexibility of inorganic materials, it still maintains a high ionic conductivity.

[0044] At the same time, the solid electrolyte of the present invention includes diffraction peaks at 24°-26°, 27°-29°, 42°-46° and 49°-54° in the X-ray diffraction spectrum (XRD), that is, it has a relatively obvious broad peak, which means that the amorphous state accounts for a high proportion in the solid electrolyte. The high proportion of amorphous state will make the solid electrolyte present the characteristics of clay or film, and it will become softer than pure hard powder, that is, it will show flexibility, which is conducive to forming close contact at the solid-solid contact interface, reducing interface impedance, improving interface stability, and facilitating the effective transmission of lithium ions, and improving the specific capacity and cycle performance of the battery.

[0045] Thus, the solid electrolyte provided by the present invention can improve the disorder of the solid electrolyte, improve the ionic conductivity, and increase the flexibility of the solid electrolyte by limiting the chemical composition and the diffraction peak 2θ in XRD, so that the solid electrolyte can form a stable interface layer when in contact with the electrode material, reducing the generation of interface reactions and by-products. This good interface contact is conducive to the effective transmission of ions, thereby improving the specific capacity and cycle performance of the battery.

[0046] In some embodiments of the present invention, A includes Y element, and the molar ratio of Y element to Ga element is 1:(0.45-1.5), for example, it can be 1:0.45, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5 or a range consisting of any two of them.

[0047] In the present invention, the Y element has a larger ionic radius and can provide a stable skeleton structure. The Ga element can enhance the overall stability of the material through its smaller ionic radius and different coordination environment, so that the solid electrolyte forms a stable crystal structure. By adjusting the molar ratio of the Y element to the Ga element, the defects and channel structure in the lattice can be optimized, thereby improving the mobility of lithium ions. The appropriate Ga element content can promote the rapid migration of ions in the lattice and improve the overall ionic conductivity. In addition, the solid electrolyte can also be made more flexible, significantly improving the situation where the solid electrolyte has poor solid-solid contact.

[0048] In some embodiments of the present invention, D comprises two or more of F, Cl and Br.

[0049] In the present invention, when D includes two or more of F, Cl and Br, since the halogen elements have higher electronegativity and different ionic radii, the mobility of lithium ions can be improved by introducing lattice defects and diversified migration channels, thereby improving the ionic conductivity of the solid electrolyte and thus improving the specific capacity and cycle performance of the battery.

[0050] In some embodiments of the present invention, D includes at least F.

[0051] It can be understood that F ions have a small ionic radius and high electronegativity, which helps to form an effective lithium ion migration channel in the solid electrolyte. The introduction of F can increase defects and vacancies in the lattice, promote the rapid migration of lithium ions, and thus improve the ionic conductivity of the solid electrolyte. In addition, the introduction of F can form a stable interface layer between the solid electrolyte and the electrode material, reduce the interface impedance, and improve the interface stability, which is beneficial to improve the cycle performance and overall efficiency of the battery.

[0052] In some embodiments of the present invention, the molar ratio of any metal element in A to Ga is (0.8-1.2):1, for example, it can be 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1 or a range consisting of any two of them.

[0053] In the present invention, by making the molar ratio of each metal element in A to Ga be (0.8-1.2):1, a uniform crystal structure can be formed, which is beneficial to reducing stress concentration and defects in the lattice, thereby improving the stability of the solid electrolyte. And the uniform distribution of metal elements can form more regular ion channels, promote the migration of lithium ions, and help improve the ionic conductivity of the material. In addition, the uniform distribution of metal elements can improve the mechanical properties of the electrolyte, so that it can better resist volume changes and mechanical stresses during the charge and discharge process, thereby improving the cycle life of the battery. It can also improve the interface contact between the solid electrolyte and the electrode material, form a stable interface layer, reduce the interface impedance, and improve the interface stability.

[0054] In some embodiments of the present invention, the solid electrolyte is in the form of clay.

[0055] It can be understood that the clay-like morphology of the solid electrolyte can provide good flexibility and plasticity, so that it can better adapt to the surface morphology of the electrode material. This morphology helps to form a close contact at the solid-solid contact interface, reduce the interface impedance, and improve the interface stability. When the solid electrolyte contacts the electrode material, it can form a stable interface layer, reduce the interface reaction and the generation of by-products. This good interface contact helps the effective transmission of lithium ions and improves the specific capacity and cycle performance of the battery.

[0056] In some embodiments of the present invention, the ionic conductivity of the solid electrolyte is greater than 1 mS / cm, for example, it can be 1 mS / cm, 1.1 mS / cm, 1.2 mS / cm, 1.3 mS / cm, 1.5 mS / cm, 1.6 mS / cm, 1.7 mS / cm, 1.8 mS / cm, 2 mS / cm, 2.5 mS / cm, 3 mS / cm, 4 mS / cm, 5 mS / cm or a range consisting of any two of them.

[0057] The ionic conductivity of the solid electrolyte in the present invention is greater than 1 mS / cm, which means that ions can migrate quickly in the electrolyte, thereby improving the specific capacity and cycle performance of the battery.

[0058] In some embodiments of the present invention, in the X-ray diffraction pattern, the half-width of the widest diffraction peak is greater than or equal to 1.35°, for example, it can be 1.35°, 1.37°, 1.4°, 1.42°, 1.45°, 1.47°, 1.5°, 1.55°, 1.57°, 1.6°, 1.65° or a range consisting of any two of them.

[0059] In the present invention, in the X-ray diffraction pattern, the width of the half-peak width of the widest diffraction peak is within the above range, indicating that the crystal structure of the solid electrolyte is imperfect, the amorphous state accounts for a large proportion, and the atomic arrangement is disordered. This disorder makes the solid electrolyte more susceptible to local deformation under the action of external force, thereby improving the flexibility of the material, facilitating the formation of close contact at the solid-solid contact interface, reducing interface impedance, improving interface stability, facilitating the effective transmission of lithium ions, and improving the specific capacity and cycle performance of the battery.

[0060] In some embodiments of the present invention, the Young's modulus of the solid electrolyte is less than or equal to 3 GPa, for example, it can be 2 GPa, 2.1 GPa, 2.2 GPa, 2.3 GPa, 2.4 GPa, 2.5 GPa, 2.6 GPa, 2.7 GPa, 2.8 GPa, 2.9 GPa, 3 GPa or a range consisting of any two of them.

[0061] The Young's modulus of the solid electrolyte in the present invention is within the above range, indicating that it has certain flexibility and elasticity, so that the solid electrolyte can further form a stable interface layer when in contact with the electrode material, reducing the generation of interface reactions and by-products. This good interface contact is conducive to the effective transmission of ions, thereby improving the specific capacity and cycle performance of the battery.

[0062] In a second aspect, the present invention provides a method for preparing the solid electrolyte as described above, comprising the following steps:

[0063] 1) grinding a raw material system including lithium halide, lithium oxide, gallium halide, and a halide containing element A to obtain a mixture;

[0064] 2) Under an inert atmosphere, the mixture is subjected to ball milling treatment and heat treatment in sequence to obtain a solid electrolyte.

[0065] In step 1) of the present invention, raw materials for forming a solid electrolyte are placed in a mortar and manually ground to complete preliminary mixing, the raw materials are uniformly mixed and the particle size is refined to obtain a mixture.

[0066] In step 2), the mixture (i.e., the mixed raw materials) is placed in an inert atmosphere, for example, in a ball milling jar protected by argon, and ball milling is performed to obtain a solid electrolyte. Ball milling under an inert atmosphere can avoid oxidation or other adverse chemical reactions and maintain the purity and stability of the material. Ball milling can further refine the particles and promote the occurrence of solid-state reactions to form a uniform solid electrolyte. Ball milling can introduce lattice defects and increase disorder, which is beneficial to improve the mobility of lithium ions. The refined particles and uniform material composition help to form a good interface contact between the electrolyte and the electrode material and reduce the interface impedance. And due to the synergistic effect of the Ga element and the monovalent halogen anion, the halide can be quickly agglomerated from the powder state, accelerating the reaction process. Heat treatment can promote the crystallization process of the material, which is beneficial to the formation of the desired crystalline phase structure, and can eliminate defects introduced during grinding or ball milling, eliminate internal stress, and is also beneficial to achieve a uniform distribution of components within the material, so that the components are fully mixed and form a uniform solid solution.

[0067] The method for preparing the solid electrolyte of the present invention produces a halide solid electrolyte that does not contain precious metals or has a low content of precious metals, which has a cost advantage. The produced solid electrolyte has high ionic conductivity and good solid-solid interface contact with electrode materials. When applied to batteries, the specific capacity and cycle performance of the batteries can be improved.

[0068] In some embodiments of the present invention, the grinding treatment time is 5 min-30 min, for example, it can be 5 min, 10 min, 15 min, 20 min, 25 min, 30 min or a range consisting of any two thereof.

[0069] In some embodiments, the rotation speed of the ball milling treatment is 400rpm-600rpm, for example, it can be 400rpm, 420rpm, 450rpm, 470rpm, 500rpm, 520rpm, 550rpm, 570rpm, 600rpm or a range consisting of any two thereof. The time of the ball milling treatment is 0.5h-4h, for example, it can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h or a range consisting of any two thereof. The ball-to-material ratio of the ball milling treatment is (10-40):1, for example, it can be 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1 or a range consisting of any two thereof.

[0070] In some embodiments, the heat treatment temperature is 150° C.-250° C., for example, 150° C., 170° C., 190° C., 200° C., 220° C., 240° C., 250° C., or any two thereof. The time is 1 h-4 h, for example, 1 h, 2 h, 2.5 h, 3 h, 4 h, or any two thereof.

[0071] In some embodiments, the halide containing element A includes yttrium halide, and the molar ratio of yttrium halide to gallium halide is 1:(0.45-1.5), for example, it can be 1:0.45, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5 or a range consisting of any two of them.

[0072] The grinding time in the present invention can ensure the full mixing of the raw materials and the initial refinement of the particles, and avoid particle agglomeration caused by excessive grinding.

[0073] The rotation speed of ball milling provides enough energy to promote effective collision and mixing between particles, which is conducive to more lattice defects and disorder, thereby improving ionic conductivity. The ball milling time can prevent excessive particle refinement. The ball-to-material ratio can optimize the energy transfer efficiency, provide greater grinding energy, and is conducive to particle refinement and uniform mixing.

[0074] The temperature and time of heat treatment can effectively eliminate defects and internal stress in the material, so that the components are evenly distributed in the material. The energy consumption during the heat treatment process is low, saving energy costs. It can also reduce the risk of thermal degradation of the material and effectively control the growth of grains.

[0075] The molar ratio of yttrium halide to gallium halide within the above range can form a stable crystal structure, optimize lattice parameters, and enhance the chemical stability and ionic conductivity of the solid electrolyte.

[0076] The preparation method of the solid electrolyte of the present invention optimizes from the material side, only requires ball milling synthesis for a very short time, avoids problems such as energy consumption and time cost caused by long-term ball milling, reduces the synthesis time by more than 90% compared with traditional ball milling, and can achieve continuous synthesis in terms of process.

[0077] In a third aspect, the present invention provides a positive electrode sheet, which includes the solid electrolyte as described above or the solid electrolyte prepared by the preparation method of the solid electrolyte as described above.

[0078] The positive electrode sheet provided by the present invention includes the above-mentioned solid electrolyte. Therefore, when this positive electrode sheet is applied to a battery, the specific capacity and cycling performance of the battery can be improved.

[0079] The present invention does not limit the preparation method of the positive electrode sheet. In a specific embodiment, the positive electrode active material, solid electrolyte, conductive agent, binder, etc. can be mixed and dispersed in a solvent to prepare a positive electrode slurry. Subsequently, the positive electrode slurry is coated on at least one functional surface of the positive electrode current collector, and after drying and rolling, a positive electrode sheet including a solid electrolyte inside the present invention is obtained; further, a dispersion liquid including a solid electrolyte can also be prepared, and the dispersion liquid is coated on the surface of the above-mentioned positive electrode sheet to obtain a positive electrode sheet including a solid electrolyte both inside and on the surface.

[0080] Alternatively, the positive electrode active material, conductive agent, binder, etc. are mixed and dispersed in a solvent to prepare a positive electrode slurry, and at the same time, a dispersion liquid including a solid electrolyte can also be prepared. Subsequently, the positive electrode slurry is coated on at least one functional surface of the positive electrode current collector, and after drying, the dispersion liquid is coated on the dried surface, and after drying again and rolling, a positive electrode sheet including a solid electrolyte on the surface of the present invention is obtained.

[0081] The present invention does not make special limitations on the positive electrode active material, conductive agent, and binder. For example, the positive electrode active material is selected from lithium iron phosphate (LiFePO4), lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese oxide (Li z Ni x Co y Mn 1-x-y O2, where 0.95 ≤ z ≤ 1.05, x > 0, y > 0, 0 < x + y < 1), lithium manganese oxide (LiMnO2), lithium nickel cobalt aluminum oxide (Li z Ni x Co y Al 1-x-y O2, where 0.95 ≤ z ≤ 1.05, x > 0, y > 0, 0.8 ≤ x + y < 1), lithium nickel cobalt manganese aluminum oxide (Li z Ni x Co y Mn w Al 1-x-y-wO2, where 0.95≤z≤1.05, x>0, y>0, w>0, 0.8≤x+y+w<1), nickel-cobalt-aluminum-tungsten materials, lithium-rich manganese-based solid solution positive electrode materials (xLi2MnO3·(1-x)LiMO2, where M=Ni / Co / Mn, 0<x<1), nickel-cobalt-acid lithium (LiNi x CoyO2, where x>0, y>0, x+y=1), lithium nickel titanium magnesium oxide (LiNi x Ti y Mg z O2, wherein x>0, y>0, z>0, x+y+z=1), lithium nickelate (Li2NiO2), spinel lithium manganate (LiMn2O4), nickel-cobalt-tungsten materials or a combination of several thereof; the conductive agent is selected from at least one of conductive carbon black, Ketjen black, conductive fiber, conductive polymer, acetylene black, carbon nanotubes, graphene, flake graphite, conductive oxides, and metal particles; the binder is selected from at least one of polyvinylidene fluoride and its copolymer derivatives, polytetrafluoroethylene and its copolymer derivatives, polyacrylic acid and its copolymer derivatives, and polyhexafluoropropylene and its copolymer derivatives.

[0082] In a fourth aspect, the present invention provides a battery, comprising the solid electrolyte as described above, or a solid electrolyte prepared by the method for preparing the solid electrolyte as described above, or a positive electrode sheet as described above.

[0083] The battery of the present invention has outstanding performance in terms of specific capacity and cycle performance.

[0084] The present invention does not limit the preparation method of the battery, for example, the positive electrode sheet, the solid electrolyte, and the negative electrode sheet can be stacked in sequence and then packaged. The positive electrode sheet, the separator, and the negative electrode sheet can also be stacked in sequence to form a basic battery cell, and then the precursor liquid is injected into it, and after sufficient infiltration, the lithium ion battery of the present invention is obtained by baking.

[0085] The positive electrode sheet and the negative electrode sheet in the battery of the present invention have no special requirements relative to the existing positive electrode sheets and negative electrode sheets in the art.

[0086] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0087] Example 1

[0088] The preparation method of the solid electrolyte of this embodiment comprises the following steps:

[0089] Weigh LiCl, YCl3, GaCl3, ZrCl4, CeCl3, AlCl3 and Li2O in a molar ratio of 0.8:0.2:0.2:0.2:0.2:0.2:0.5, put the weighed raw materials in a mortar, grind them manually for 10 minutes for preliminary mixing to obtain a mixture; under argon protection, ball mill the mixture for 2 hours, wherein the ball mill speed is 500rpm, and the ball-to-material ratio is 25:1, to obtain a solid electrolyte precursor. The solid electrolyte precursor is heat-treated at 200°C for 2 hours to obtain a solid electrolyte. The solid electrolyte is in the form of clay. Figure 1 As shown, in the X-ray diffraction pattern, the diffraction peaks at 2θ are located at 24°-26°, 27°-29°, 42°-46° and 49°-54°.

[0090] Example 2

[0091] The preparation method of the solid electrolyte of Example 2 is basically the same as that of Example 1, except that LiF, YF3, GaF3, ZrF4, CeF3, AlF3 and Li2O are weighed in a molar ratio of 0.8:0.2:0.2:0.2:0.2:0.2:0.5. The solid electrolyte obtained is in the form of clay. Figure 2 As shown, in the X-ray diffraction pattern, the diffraction peaks at 2θ are located at 24°-26°, 27°-29°, 42°-46° and 49°-54°.

[0092] Example 3

[0093] The preparation method of the solid electrolyte of Example 3 is basically the same as that of Example 1, except that LiF, YF3, GaF3, ZrF4, CeF3, AlF3, LiCl and Li2O are weighed in a molar ratio of 0.4:0.2:0.2:0.2:0.2:0.2:0.5:0.25. The solid electrolyte obtained is in the form of clay. Figure 3 As shown, in the X-ray diffraction pattern, the diffraction peaks at 2θ are located at 24°-26°, 27°-29°, 42°-46° and 49°-54°.

[0094] Example 4

[0095] The preparation method of the solid electrolyte of Example 4 is basically the same as that of Example 1, except that LiF, YF3, GaF3, ZrF4, CeF3, AlF3, LiCl and Li2O are weighed at a molar ratio of 0.4:0.35:0.35:0.1:0.1:0.1:0.5:0.25. The solid electrolyte obtained is in the form of clay. In the X-ray diffraction spectrum, it includes diffraction peaks at 2θ located at 24°-26°, 27°-29°, 42°-46° and 49°-54°.

[0096] Example 5

[0097] The preparation method of the solid electrolyte of Example 5 is basically the same as that of Example 1, except that LiF, YF3, GaF3, ZrF4, CeF3, AlF3, LiCl and Li2O are weighed in a molar ratio of 0.4:0.1:0.3:0.2:0.2:0.2:0.5:0.25. The obtained solid electrolyte has a clay-like morphology. In the X-ray diffraction spectrum, it includes diffraction peaks at 2θ located at 24°-26°, 27°-29°, 42°-46° and 49°-54°.

[0098] Example 6

[0099] The preparation method of the solid electrolyte of Example 6 is basically the same as that of Example 1, except that LiF, YF3, GaF3, ZrF4, CeF3, AlF3, LiCl and Li2O are weighed in a molar ratio of 0.4:0.3:0.1:0.2:0.2:0.2:0.5:0.25. The obtained solid electrolyte has a clay-like morphology. In the X-ray diffraction spectrum, it includes diffraction peaks at 2θ located at 24°-26°, 27°-29°, 42°-46° and 49°-54°.

[0100] Example 7

[0101] The preparation method of the solid electrolyte of Example 7 is basically the same as that of Example 1, except that LiF, YF3, GaF3, ZrF4, CeF3, AlF3, LiCl and Li2O are weighed in a molar ratio of 0.4:0.27:0.13:0.2:0.2:0.2:0.5:0.25. The solid electrolyte obtained is in the form of clay. In the X-ray diffraction spectrum, it includes diffraction peaks at 2θ located at 24°-26°, 27°-29°, 42°-46° and 49°-54°.

[0102] Example 8

[0103] The preparation method of the solid electrolyte of Example 8 is basically the same as that of Example 1, except that LiF, YF3, GaF3, ZrF4, CeF3, AlF3, LiCl and Li2O are weighed in a molar ratio of 0.4:0.17:0.23:0.2:0.2:0.2:0.5:0.25. The obtained solid electrolyte has a clay-like morphology. In the X-ray diffraction spectrum, it includes diffraction peaks at 2θ located at 24°-26°, 27°-29°, 42°-46° and 49°-54°.

[0104] Example 9

[0105] The preparation method of the solid electrolyte of Example 9 is basically the same as that of Example 3, except that the grinding time is changed to 5 min, the ball milling speed is 400 rpm, the time is 0.5 h, the ball-to-material ratio is 40:1, and the solid electrolyte precursor is heat-treated at 250 ° C for 1 h. The obtained solid electrolyte has a clay-like morphology. In the X-ray diffraction spectrum, it includes diffraction peaks at 2θ located at 24°-26°, 27°-29°, 42°-46° and 49°-54°.

[0106] Example 10

[0107] The preparation method of the solid electrolyte of Example 10 is basically the same as that of Example 3, except that the grinding time is changed to 30 min, the ball milling speed is 600 rpm, the time is 4 h, the ball-to-material ratio is 10:1, and the solid electrolyte precursor is heat-treated at 150 ° C for 4 h. The obtained solid electrolyte has a clay-like morphology. In the X-ray diffraction spectrum, it includes diffraction peaks at 2θ located at 24°-26°, 27°-29°, 42°-46° and 49°-54°.

[0108] Embodiment 11

[0109] The preparation method of the solid electrolyte of Example 11 is basically the same as that of Example 1, except that LiF, YF3, GaF3, ZrF4, InF3, HoF3, LiCl and Li2O are weighed at a molar ratio of 0.4:0.2:0.2:0.2:0.2:0.2:0.5:0.25. The solid electrolyte obtained is in the form of clay. In the X-ray diffraction spectrum, it includes diffraction peaks at 2θ located at 24°-26°, 27°-29°, 42°-46° and 49°-54°.

[0110] Example 12

[0111] The preparation method of the solid electrolyte of Example 12 is basically the same as that of Example 1, except that LiF, YF3, GaF3, ZrF4, TaF5, NbF5, LiBr and Li2O are weighed at a molar ratio of 0.4:0.2:0.2:0.2:0.2:0.2:0.5:0.25. The solid electrolyte obtained is in the form of clay. In the X-ray diffraction spectrum, it includes diffraction peaks at 2θ located at 24°-26°, 27°-29°, 42°-46° and 49°-54°.

[0112] Embodiment 13

[0113] The preparation method of the solid electrolyte of Example 13 is basically the same as that of Example 1, except that LiCl, YCl3, GaCl3, ZrCl4, CeCl3, AlCl3 and Li2O are weighed at a molar ratio of 0.8:0.2:0.2:0.2:0.2:0.2:0.4. The solid electrolyte obtained is in the form of clay. In the X-ray diffraction spectrum, it includes diffraction peaks at 2θ located at 24°-26°, 27°-29°, 42°-46° and 49°-54°.

[0114] Comparative Example 1

[0115] The preparation method of the solid electrolyte of Comparative Example 1 comprises the following steps:

[0116] LiCl and YCl3 were weighed at a molar ratio of 3:1, and the weighed raw materials were mixed and ball milled for 40 hours at a ball milling speed of 500 rpm and a ball-to-material ratio of 30:1 to obtain a solid electrolyte. The solid electrolyte is in powder form. Figure 1 As shown, in the X-ray diffraction pattern, the diffraction peaks at 2θ are located at 31°-31.6°, 40.6°-41.2°, and 48.4°-49.0°.

[0117] Comparative Example 2

[0118] The preparation method of the solid electrolyte of Comparative Example 2 comprises the following steps:

[0119] LiCl and InCl3 were weighed in a molar ratio of 3:1, and the weighed raw materials were mixed and ball milled for 40 hours at a ball milling speed of 500 rpm and a ball-to-material ratio of 30:1. The ball-milled sample was heat treated at 260°C for 5 hours to obtain a solid electrolyte. The solid electrolyte is in powder form. Figure 4 As shown, in the X-ray diffraction pattern, the diffraction peaks at 2θ are located at 14.5°-15.1°, 34.0°-34.7°, and 49.1°-50.0°.

[0120] Comparative Example 3

[0121] The preparation method of the solid electrolyte of Comparative Example 3 is basically the same as that of Example 1, except that LiF, YF3, GaF3, ZrF4, CeF3, AlF3 and LiCl are weighed in a molar ratio of 0.4:0.2:0.2:0.2:0.2:0.2:0.5. The solid electrolyte is in powder form. Figure 5 As shown, in the X-ray diffraction pattern, the diffraction peaks at 2θ are located at 25.8°-26.1°, 27.2°-28.1°, and 46.8°-48.1°.

[0122] Comparative Example 4

[0123] The preparation method of the solid electrolyte of Comparative Example 4 is basically the same as that of Example 1, except that LiF, YF3, ZrF4, CeF3, AlF3, LiCl and Li2O are weighed in a molar ratio of 0.4:0.25:0.25:0.25:0.25:0.5:0.25. The solid electrolyte is in powder form. Figure 6 As shown, in the X-ray diffraction pattern, the diffraction peaks at 2θ are located at 25.6°-26.3°, 27.3°-28.3°, and 34.6°-35.4°.

[0124] Comparative Example 5

[0125] The preparation method of the solid electrolyte of Comparative Example 5 is basically the same as that of Example 1, except that Li2O and Ga2O3 are weighed in a molar ratio of 1:1. The solid electrolyte is in powder form. Figure 7 As shown, in the X-ray diffraction pattern, the diffraction peaks at 2θ are located at 30.5°-30.8°, 35.4°-35.7°, and 50.9°-51.3°.

[0126] Test example:

[0127] 1. Determination of the types and contents of elements in solid electrolytes: Take 200 mg of solid electrolyte sample and place it in a sealed instrument, further seal it with sealing tape to avoid exposure to the air, and then transfer it to an ICP element tester for ICP characterization to analyze the elemental composition and corresponding content.

[0128] 2. XRD test: Take a certain amount of solid electrolyte sample and place it on the XRD sample table, and seal it with KAPTON tape to avoid moisture interference with the characteristic peaks of the sample. The light used in the XRD test is Cu-Kα radiation, and the X-ray diffraction analysis is performed using Bruker's D Advance. Determine the position of the widest diffraction peak in the XRD spectrum and test its half-peak width.

[0129] 3. Ionic conductivity: 200 mg of solid electrolyte was placed in a solid mold, and a 3-ton pressure was used to press the tablets, and the pressure was maintained for 3 minutes. Then, a carbon-coated aluminum foil was attached to each side of the pressed solid electrolyte sheet as a current collector, and the battery was assembled and pressurized on the outside. The test method was the AC impedance method, and the test frequency was 10 MHz-1 Hz.

[0130] 4. Specific capacity: Batteries were prepared using the solid electrolytes obtained in the examples and comparative examples, specifically comprising: mixing the solid electrolyte, the ternary positive electrode material Ni83 and the conductive carbon in a mass ratio of 30:70:3 to obtain a positive electrode composite material; using Li-In alloy as the negative electrode material; weighing a certain amount of solid electrolyte, pouring it into a battery mold, pressing it into a sheet under a certain pressure to obtain a solid electrolyte layer, and placing the solid electrolyte layer between the positive electrode sheet formed by the positive electrode composite material and the negative electrode sheet formed by the negative electrode material to obtain a battery.

[0131] At 25°C, the batteries were charged at a constant current of 0.1C / 1C to 4.3V, and then charged at a constant voltage of 4.3V to a current equal to 0.05C. The charging capacity at this time was recorded as the first-cycle charging capacity. After that, the batteries were allowed to stand for 5 minutes, and then discharged at a constant current of 0.1C / 1C to a voltage of 2.5V. The discharge capacity was recorded as the first-cycle discharge capacity of the battery.

[0132] 5. Cycle performance: At 25°C, the battery is charged to the upper limit voltage at a constant current of 1C, then charged to the lower limit voltage at a constant voltage of 0.5C, and then discharged to the lower limit voltage at a discharge rate of 1C. Repeat this charge and discharge cycle 100 times, and measure the discharge capacity Q1 at the first cycle and the discharge capacity Q at the 100th cycle. 100 The capacity retention rate after 100 cycles is Q=Q 100 / Q1*100%.

[0133] 6. Young's modulus test: The corresponding solid electrolyte samples were tested by atomic force microscopy using quantitative nano-imaging mode to make the probe and sample interact with each other and obtain the Young's modulus data. The constant loading rate was 400 nm·S -1 .

[0134] Figure 1 1 and 2 are XRD diagrams of the solid electrolytes of Example 1 and Comparative Example 1 of the present invention.

[0135] from Figure 1It can be seen that the solid electrolyte of comparative example 1 has a higher crystalline content, and the corresponding characteristic peak is sharper; the solid electrolyte of embodiment 1 increases the amorphous content, and the corresponding characteristic peak is wider. And the ratio of the peak intensity of the diffraction peak of the solid electrolyte of embodiment 1 at 27°-29° to the peak intensity of the diffraction peak of the solid electrolyte of comparative example 1 at 31°-31.6° is 1:7.86, indicating that the peak intensity of the diffraction peak of the solid electrolyte of embodiment 1 is weak, the amorphous content is high, and the solid electrolyte presents a clay-like state.

[0136] Figure 8 a is the morphology of the solid electrolyte of Example 1 of the present invention, and b is the morphology of the solid electrolyte of Comparative Example 1 of the present invention.

[0137] from Figure 8 It can be seen that the solid electrolyte of Example 1 is in a significant clay-like state and has a certain flexibility; the solid electrolyte of Comparative Example 1 is in a powdery state.

[0138] Table 1

[0139]

[0140] As can be seen from Table 1, the solid electrolyte provided by the present invention can improve the disorder of the solid electrolyte, improve the ionic conductivity, and increase the flexibility of the solid electrolyte by limiting the chemical composition and the diffraction peak 2θ in XRD, so that the solid electrolyte can form a stable interface layer when in contact with the electrode material, reducing the generation of interface reactions and by-products. This good interface contact is conducive to the effective transmission of ions, thereby improving the specific capacity and cycle performance of the battery.

[0141] From the comparison between Examples 1-13 and Comparative Examples 1-5, it can be seen that the solid electrolyte provided by the present invention has a wider half-peak width and a lower Young's modulus, indicating that the amorphous state accounts for a larger proportion and has stronger flexibility.

[0142] The high entropy halide solid electrolytes synthesized in Examples 1-13 have significantly improved ionic conductivity compared with the two most typical halide solid electrolytes in Comparative Examples 1-2, and the synthesis time and cost are greatly reduced.

[0143] Compared with Examples 1-2, Example 3 further introduces anion species to enhance the disorder of the crystal structure, thereby inducing more carriers and crystal defects, significantly enhancing the lithium ion conductivity, and fully demonstrating the advantages of high entropy materials.

[0144] Compared with Example 3, Examples 4, 7, and 8 changed the proportion of metal elements, and the ionic conductivity decreased to varying degrees, indicating that the molar ratio of any metal element in A to Ga is (0.8-1.2):1, which is more conducive to the transmission of lithium ions.

[0145] Compared with Example 3, Example 5-6 changed the ratio of Y element and Ga element in the metal elements, and the ionic conductivity decreased significantly, indicating that the molar ratio of Y element and Ga element was 1: (0.45-1.5), which was more conducive to the transmission of lithium ions.

[0146] After removing the O element and the Ga element in Comparative Examples 3 and 4, respectively, the ionic conductivity decreased significantly, which illustrates the importance of the O element and the Ga element in the high entropy halide solid electrolyte of the present invention.

[0147] Compared with Examples 3-12, Example 1 has a higher content of O element, the half-width of the widest diffraction peak is less than 1.35° and the Young's modulus is greater than 3 GPa, indicating that its amorphous proportion is less than that of Example 3-12, and its flexibility is worse than that of Example 3-12, resulting in poor specific capacity and cycle performance of the battery.

[0148] Compared with Example 1, Example 13 has a slightly lower content of O element, and the half-width of the widest diffraction peak is less than 1.35°, but the Young's modulus is less than 3 GPa, so that the specific capacity and cycle performance of the battery are better than those of Example 1.

[0149] Finally, it should be noted that those skilled in the art will readily conceive of other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses or adaptations of the present invention, which follow the general principles of the present invention and include common knowledge or customary technical means in the art not disclosed by the present invention, are not limited to the precise structure described above and shown in the drawings, and may be modified and changed in various ways without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A solid electrolyte, characterized in that The chemical composition of the solid electrolyte is Li x Ga y A a D b O c , wherein 0.5≤x≤2.0, 0.1≤y≤0.5, 0.1≤a≤1, 3.5≤b≤5, 0.25≤c≤1.5; A includes four or more of Y, In, Al, La, Ce, Ho, Zr, Ta, and Nb, and D includes one or more of F, Cl, and Br; The X-ray diffraction pattern includes diffraction peaks at 2θ located at 24°-26°, 27°-29°, 42°-46° and 49°-54°.

2. The solid electrolyte according to claim 1, characterized in that The A includes a Y element, and the molar ratio of the Y element to the Ga element is 1:(0.45-1.5).

3. The solid electrolyte according to claim 1 or 2, characterized in that The D includes two or more of F, Cl and Br.

4. The solid electrolyte according to any one of claims 1 to 3, characterized in that The D includes at least F.

5. The solid electrolyte according to any one of claims 1 to 4, characterized in that The molar ratio of any one of the metal elements in A to Ga is (0.8-1.2):

1.

6. The solid electrolyte according to any one of claims 1 to 5, characterized in that The solid electrolyte is in the form of clay.

7. The solid electrolyte according to any one of claims 1 to 6, characterized in that The ionic conductivity of the solid electrolyte is greater than 1 mS / cm.

8. The solid electrolyte according to any one of claims 1 to 7, characterized in that In the X-ray diffraction pattern, the half-peak width of the broadest diffraction peak is greater than or equal to 1.35°.

9. The solid electrolyte according to any one of claims 1 to 8, characterized in that The Young's modulus of the solid electrolyte is less than or equal to 3 GPa.

10. A method for preparing a solid electrolyte according to any one of claims 1 to 9, characterized in that: The following steps are involved: 1) grinding a raw material system including lithium halide, lithium oxide, gallium halide, and a halide containing element A to obtain a mixture; 2) Under an inert atmosphere, the mixture is subjected to ball milling treatment and heat treatment in sequence to obtain the solid electrolyte.

11. The method for preparing a solid electrolyte according to claim 10, characterized in that: The grinding time is 5min-30min; And / or, the rotation speed of the ball milling treatment is 400rpm-600rpm, the time is 0.5h-4h, and the ball-to-material ratio is (10-40):1; And / or, the heat treatment temperature is 150°C-250°C, and the time is 1h-4h; And / or, the halide containing element A includes yttrium halide, and the molar ratio of the yttrium halide to the gallium halide is 1:(0.45-1.5).

12. A positive electrode sheet, characterized in that: A solid electrolyte comprising the solid electrolyte according to any one of claims 1 to 9 or a solid electrolyte prepared by the preparation method of the solid electrolyte according to claim 10 or 11.

13. A battery, characterized in that: A solid electrolyte comprising the solid electrolyte according to any one of claims 1 to 9 or a solid electrolyte prepared by the method for preparing the solid electrolyte according to claim 10 or 11 or a positive electrode sheet according to claim 12.

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