Halide solid electrolyte, preparation method thereof and all-solid-state battery

Abstract

The invention provides a halide solid electrolyte, a preparation method thereof and an all-solid-state battery, and relates to the technical field of batteries. The method comprises the steps that LiX and TMXb are mixed in an inert gas environment, precursor powder is obtained, TM represents at least three transition metal elements, X represents a halogen element, and b is larger than or equal to 2 and smaller than or equal to 7; then carrying out non-crystallization treatment on the precursor powder to obtain a solid electrolyte powder precursor; and finally, sintering the solid electrolyte powder precursor in an inert gas environment to obtain the halide solid electrolyte with the molecular formula of Li3TMX3 + a, and a represents the average value of valence states of transition metal elements. Through the method, the prepared halide solid electrolyte has high ionic conductivity, high electronic conductivity and excellent interface stability and electrochemical stability to a positive electrode material.

Description

Technical Field

[0001] This application relates to the field of batteries, and more particularly to a halide solid electrolyte, its preparation method, and an all-solid-state battery. Background Technology

[0002] Halogen solid electrolytes have become a research hotspot due to their advantages such as high ionic conductivity, low synthesis temperature, excellent mechanical ductility, and good interfacial contact with cathode materials.

[0003] In existing technologies, a conductive network is constructed by introducing an additional conductive agent at the positive electrode to compensate for the insufficient electronic conductivity of halide solid electrolytes. However, the introduction of the conductive agent will lead to a significant increase in the positive electrode impedance in all-solid-state batteries, a significant increase in polarization of all-solid-state batteries, and a significant reduction in the electrochemical stability and interfacial stability of halide solid electrolytes at the positive electrode.

[0004] In summary, providing a halide solid electrolyte that combines high electronic conductivity with excellent interfacial and electrochemical stability to cathode materials is an urgent technical problem to be solved. Summary of the Invention

[0005] This application provides a halide solid electrolyte, its preparation method, and an all-solid-state battery, which can improve the electronic conductivity of the halide solid electrolyte and its interfacial stability with the cathode material.

[0006] In a first aspect, embodiments of this application provide a halide solid electrolyte, wherein the molecular formula of the halide solid electrolyte is Li3TMX. 3+a ;

[0007] Wherein, TM represents a transition metal element, X represents a halogen element, TM includes at least three transition metal elements, and a represents the average valence state of the transition metal element.

[0008] In one possible implementation, the TM includes at least three of the following elements:

[0009] Ti, Ni, Mn, Co, Fe, Cr, V, Y, Zr, Nb, Ta, Sc, Hf and W.

[0010] In one possible implementation, X includes at least one of the following elements:

[0011] F, Cl, Br, and I.

[0012] Secondly, embodiments of this application provide a method for preparing a halide solid electrolyte, comprising:

[0013] LiX and TMX bThe mixture is mixed in an inert gas environment to obtain a precursor powder, wherein TM represents a transition metal element, X represents a halogen element, and the value of b ranges from 2 to b to 7. The TM includes at least three transition metal elements.

[0014] The precursor powder is subjected to amorphization treatment to obtain a solid electrolyte powder precursor;

[0015] The solid electrolyte powder precursor is sintered in an inert gas environment to obtain a halide solid electrolyte, wherein the molecular formula of the halide solid electrolyte is Li3TMX. 3+a , where 'a' represents the average valence state of the transition metal element.

[0016] In one possible implementation, the TM includes at least three of the following elements:

[0017] Ti, Ni, Mn, Co, Fe, Cr, V, Y, Zr, Nb, Ta, Sc, Hf and W;

[0018] And / or,

[0019] The X includes at least one of the following elements:

[0020] F, Cl, Br, and I.

[0021] In one possible implementation, the method further includes:

[0022] The LiX and TMX were obtained by weighing at a molar ratio of 3:1. b .

[0023] In one possible implementation, the amorphization treatment of the precursor powder to obtain a solid electrolyte powder precursor includes:

[0024] The precursor powder is placed in a ball mill jar and ball milled to obtain the solid electrolyte powder precursor.

[0025] In one possible implementation, the ball milling process is carried out for 2 to 30 hours and / or at a speed of 100 to 800 rpm.

[0026] In one possible implementation, the sintering time is 1 to 20 hours and / or the sintering temperature is 200 to 500°C.

[0027] Thirdly, embodiments of this application provide an all-solid-state battery, including, as in the first aspect and / or various possible halide solid electrolytes of the first aspect, or, halide solid electrolytes prepared according to the second aspect and / or various possible embodiments of the second aspect.

[0028] This application provides a halide solid electrolyte, its preparation method, and an all-solid-state battery. The method involves preparing lithium halide (LiX) and a halide (TMX) composed of at least three transition metal elements in an inert gas environment. b (The value of b is in the range of 2 ≤ b ≤ 7) The mixture is then used to obtain precursor powder; subsequently, the precursor powder is subjected to amorphization treatment to obtain an amorphous solid electrolyte powder precursor. Finally, the solid electrolyte powder precursor is sintered in an inert gas environment to obtain the final product with the molecular formula Li3TMX. 3+a The halide solid electrolyte is prepared by the above method, where 'a' represents the average valence state of various transition metal elements. The prepared halide solid electrolyte exhibits high ionic conductivity, electronic conductivity, and excellent interfacial and electrochemical stability with respect to the cathode material. Attached Figure Description

[0029] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0030] Figure 1 This is a schematic flowchart illustrating a method for preparing a halide solid electrolyte provided in this application.

[0031] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0033] The application background of this application is explained as follows:

[0034] With the rapid development of new energy vehicles and energy storage systems, the energy density and safety of lithium-ion batteries have become key factors restricting their large-scale application. Traditional liquid electrolyte batteries have the risk of thermal runaway and limited room for energy density improvement, making it difficult to meet the demand for high-energy-density batteries.

[0035] Solid-state batteries are considered the preferred solution for next-generation high-safety, high-energy-density batteries due to their resistance to combustion and decomposition when exposed to fire and their leak-free characteristics. Solid electrolytes mainly include sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, and halide solid electrolytes. Among them, halide solid electrolytes have become a research hotspot due to their advantages such as high ionic conductivity, low synthesis temperature, excellent mechanical ductility, and good interfacial compatibility with cathode materials. In particular, compared to sulfide solid electrolytes, halide solid electrolytes exhibit better electrochemical stability to cathode active materials and do not react to generate toxic hydrogen sulfide (H2S) gas, thus better meeting the dual core requirements of high-voltage all-solid-state batteries for electrolyte safety and interfacial compatibility. However, halide solid electrolytes have very low electronic conductivity (10⁻⁶ Ω·cm). -9 ~10 -10 The S / cm ratio severely restricts its practical application in high-performance all-solid-state batteries and other energy storage devices.

[0036] In existing technologies, a conductive agent is introduced into the positive electrode, allowing it to overlap with the active material and the halide solid electrolyte to form a conductive network. This network connects the previously isolated active material particles, enabling electrons to be rapidly transported to the reaction sites of each particle and efficiently transferred to the current collector. Even if the halide solid electrolyte itself has poor electronic conductivity, electrons can bypass the electrolyte phase through the conductive network, achieving efficient electron transport throughout the positive electrode and effectively compensating for the insufficient electronic conductivity of the halide solid electrolyte, ensuring the full conduction of the electrochemical reaction at the positive electrode. However, on the one hand, the introduction of the conductive agent can cause the decomposition of the halide solid electrolyte; on the other hand, the three-phase interface problem exists between the active material, the halide solid electrolyte, and the conductive agent in the composite positive electrode layer. Both of these factors lead to a significant increase in the positive electrode impedance in the all-solid-state battery, a significant increase in polarization, and a significant decrease in the electrochemical stability of the halide solid electrolyte at the positive electrode.

[0037] Therefore, providing a halide solid electrolyte that combines high electronic conductivity with excellent electrochemical and interfacial stability at the cathode is an urgent technical problem to be solved.

[0038] Based on the aforementioned technical problems, the inventors, in the process of researching halide solid electrolytes and their preparation methods, discovered that by introducing a high-entropy strategy of co-doping with at least three transition metal elements having unfilled d orbitals, the ionic and electronic conductivity of halide solid electrolytes can be simultaneously improved, reducing or eliminating dependence on conductive agents. At the same time, the oxidation kinetics of halide solid electrolytes are suppressed, enhancing their interfacial stability with the cathode and their electrochemical stability. Based on this, this application provides a halide solid electrolyte, its preparation method, and an all-solid-state battery.

[0039] The technical solution of this application and how it solves the above-mentioned technical problems will be described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will be described below with reference to the accompanying drawings.

[0040] This application provides a halide solid electrolyte with the molecular formula Li3TMX. 3+a Where TM represents a transition metal element, X represents a halogen element, TM includes at least three transition metal elements, and a represents the average valence state of the transition metal element.

[0041] Transition metal elements (TM) refer to metals in the d-block and ds-block of the periodic table, covering most metals from Group 3 to Group 12. Their core characteristic is that the number of electrons in the outermost shell of their atoms is usually 1 or 2, and the electrons in the penultimate d orbital are not completely filled. This electronic structure endows transition metal elements with variable valence, rich electronic configurations, and excellent coordination ability. It can effectively solve problems such as increased cathode impedance caused by the three-phase interface of composite cathodes and conductive networks, intensified polarization of all-solid-state batteries, and reduced electrochemical stability of the cathode by halide solid electrolytes. It improves the ionic conductivity, electronic conductivity, and active material loading of halide solid electrolytes, meeting the requirements of all-solid-state batteries for efficient conductive networks, thereby improving the energy density and performance of all-solid-state batteries.

[0042] In one possible implementation, TM includes at least three of the following elements:

[0043] Ti, Ni, Mn, Co, Fe, Cr, V, Y, Zr, Nb, Ta, Sc, Hf and W.

[0044] In other words, TM includes three or more transition metal elements. Taking nickel (Ni) as an example, Ni is located in Group VIII of Period 4 of the periodic table. Its outermost d orbitals have incompletely filled electron configurations, resulting in variable valence states, commonly +2 and +3. This allows Ni to form stable coordination structures with titanium, lithium, and halogens, participating in charge balance regulation of the halide solid electrolyte crystal structure through its variable valence states and optimizing ion transport channels within the crystal. The valence differences between different transition metals can construct energy level ladders for electronic transitions, lowering the energy barrier for electron transport and improving the ionic and electronic conductivity of the halide solid electrolyte. Simultaneously, the coordination between Ni and halogens enhances the structural stability of the halide solid electrolyte, improves the interfacial compatibility between the halide solid electrolyte and the cathode, and reduces interfacial impedance. In addition, Ni forms a synergistic effect with other transition metal elements, which helps to suppress the oxidation kinetics of halide solid electrolytes, effectively solves the matching problem between halide solid electrolytes and high-voltage cathodes, further improves the electrochemical stability and interfacial stability of halide solid electrolytes to cathode materials, reduces polarization of all-solid-state batteries, lowers the impedance of all-solid-state batteries, and improves the utilization rate of active materials, thereby improving the energy density and performance of all-solid-state batteries.

[0045] Halogen elements (X) are nonmetallic elements in Group VIIA of the periodic table. They all have seven electrons in their outermost shell, giving them a strong electron-gaining tendency and making them extremely chemically reactive, readily combining with metallic elements to form salt compounds. As key constituent elements of halide solid electrolytes, halogen elements participate in the construction of the crystal structure of halide solid electrolytes through coordination with lithium and transition metals. Their own electronic properties and atomic radii directly affect the size of the electrolyte's ion transport channels and charge distribution, thus significantly influencing the core performance of halide solid electrolytes, such as ionic conductivity, electronic conductivity, electrochemical stability, and interfacial stability. Ultimately, this contributes to achieving lower impedance, higher energy density, and superior cycle performance in all-solid-state batteries.

[0046] In one possible implementation, X includes at least one of the following elements:

[0047] F, Cl, Br, and I.

[0048] Taking fluorine (F) as an example, fluorine (F) is the halogen element with the smallest atomic number and the smallest atomic radius. It is located in the second period and group VIIA of the periodic table. Its outermost shell has 7 electrons. Due to its small atomic radius and relatively concentrated nuclear charge, fluorine (F) has the strongest electronegativity of all elements. It has an extremely strong ability to gain electrons and is extremely chemically active. It can form stable ionic or coordinate bonds with lithium, titanium and transition metal elements. It is the core halogen component that constitutes the crystal structure of halide solid electrolytes. Fluorine atoms, with their extremely small atomic radius, can effectively reduce the steric hindrance of ion and electron transport channels in the crystal structure of halide solid electrolytes, significantly improving the migration rate of lithium ions and thus enhancing the ionic and electronic conductivity of halide solid electrolytes. Simultaneously, the strong bonding between fluorine and transition metal elements can enhance the structural and thermal stability of halide solid electrolytes, improve the interfacial compatibility between halide solid electrolytes and cathode materials, and reduce interfacial impedance. Furthermore, the introduction of fluorine can also suppress side reactions between the electrolyte and cathode by regulating the electronic band structure of the electrolyte, thereby improving the electrochemical stability of halide solid electrolytes. This contributes to achieving higher energy density, superior cycle performance, and more reliable safety performance in all-solid-state batteries.

[0049] In one possible implementation, 'a' represents the average valence state of the transition metal element.

[0050] Understandably, if TM includes three or more transition metal elements, then the value of 'a' is the average of the valence states of at least three transition metal elements.

[0051] For example, if TM includes three transition metal elements—Ti, Ta, and Ni—with valences of +3, +4, and +2 respectively, then a = (3 + 4 + 2) / 3 = 3; if TM includes four transition metal elements—Mn, V, Y, and W—with valences of +5, +3, +3, and +6 respectively, then a = (5 + 3 + 3 + 6) / 4 = 4.25; if TM includes Mn... If TM includes five transition metal elements: Fe, Co, Cr, and Zr, with valences of +7, +3, +3, +3, and +4 respectively, then a = (7 + 3 + 3 + 3 + 4) / 5 = 4. If TM includes four transition metal elements: Ti, Nb, Sc, and Hf, with valences of +3, +5, +3, and +4 respectively, then a = (3 + 5 + 3 + 4) / 4 = 3.75.

[0052] The halide solid electrolyte provided in this application embodiment has the molecular formula Li3TMX. 3+aIn this formula, TM represents a transition metal element, including at least three elements selected from Ti, Ni, Mn, Co, Fe, Cr, V, Y, Zr, Nb, Ta, Sc, Hf, and W; X represents a halogen element, including at least one element selected from F, Cl, Br, and I; and a represents the average valence state of the transition metal element. This halide solid electrolyte possesses high electronic conductivity, ionic conductivity, and excellent electrochemical and interfacial stability for the cathode material. It can also reduce polarization and impedance in all-solid-state batteries, and improve the utilization rate of active materials, thereby enhancing the energy density and performance of all-solid-state batteries.

[0053] Figure 1 A schematic flowchart of a method for preparing a halide solid electrolyte provided in this application is shown below. Figure 1 As shown, the method includes:

[0054] S101: Incorporating LiX and TMX b The mixture is mixed in an inert gas environment to obtain a precursor powder, wherein TM represents a transition metal element, X represents a halogen element, b has a value range of 2≤b≤7, and TM includes at least three transition metal elements.

[0055] In this step, X represents a halogen element, LiX refers to lithium halides, which are the core source of lithium ions in halide solid electrolytes; TM represents a transition metal element, which includes at least three transition metal elements, TMX b This refers to halides of transition metals, where 'b' represents the number of halogen atoms bonded to a single transition metal atom. Inert gases are chemically very inert gases, such as argon, neon, helium, and nitrogen. LiX and TMX are also mentioned. b This provides a material basis for the synthesis of the target halide solid electrolyte.

[0056] In one possible implementation, TM includes at least three of the following elements:

[0057] Ti, Ni, Mn, Co, Fe, Cr, V, Y, Zr, Nb, Ta, Sc, Hf and W;

[0058] And / or,

[0059] X includes at least one of the following elements:

[0060] F, Cl, Br, and I.

[0061] b can take values ​​of 2, 3, 4, 5, 6, or 7. For example, if X includes Cl and TM includes Ti, Ni, Co, Cr, and Fe, then the raw materials for the halide solid electrolyte can include LiCl, TiCl3, NiCl2, CrCl3, CoCl3, and FeCl3. Among these, Ti, as a transition metal element, has valences of +4, +3, and +2 (+4 is the most common, followed by +3, and +2 is rare). Furthermore, TMX... b It can also be MnCl5, TaI4, HfF4, NiBr2, CoI3, WI6, MnCl7, TiF2, or TiBr3, etc. That is, the raw materials of halide solid electrolytes can include LiCl and at least three of MnCl5, TaI4, HfF4, NiBr2, CoI3, WI6, MnCl7, TiF2, and TiBr3.

[0062] Specifically, to ensure that the halide solid electrolyte is not contaminated or deteriorated during the preparation process, LiX and TMX are used. b Mixing in an inert gas environment allows the concentrated raw materials to be evenly dispersed together, forming precursor powder with a relatively uniform chemical composition, providing a material basis for the preparation of halide solid electrolytes.

[0063] S102: The precursor powder is subjected to amorphization treatment to obtain a solid electrolyte powder precursor.

[0064] In this step, amorphization is used to disrupt the original crystalline structure of the raw material components in the precursor powder, transforming it into an amorphous structure with long-range disorder and short-range order. The amorphous structure reduces the resistance encountered by ions and electrons as they move within the electrolyte; its lack of significant grain boundary characteristics helps reduce the hindering effect of grain boundaries, improving ionic and electronic conductivity. This provides higher activity and more uniform reaction sites for the formation of the target electrolyte's crystal configuration during subsequent crystallization. Commonly used amorphization methods include mechanical ball milling, melt quenching, and vapor deposition. The resulting solid electrolyte powder precursor is a transitional form of the target electrolyte (halide solid electrolyte).

[0065] For example, in the amorphization treatment of precursor powder by melt quenching, the precursor powder is first heated to a molten state to completely disintegrate the original crystal structure, and then rapidly cooled so that the atoms do not have time to rearrange to form crystals, thus obtaining an amorphous solid electrolyte powder precursor. In the amorphization treatment of precursor powder by mechanical ball milling, the precursor powder is placed in a ball mill jar, and the high-speed rotation and collision of the grinding balls cause the precursor powder particles to be subjected to strong mechanical force, destroying the crystal structure and obtaining an amorphous solid electrolyte powder precursor.

[0066] In one possible implementation, the precursor powder is placed in a ball mill jar and ball milled to obtain a solid electrolyte powder precursor.

[0067] Optionally, during ball milling, the milling time is 2 to 30 hours, and / or the milling speed is 100 to 800 rpm.

[0068] The grinding jar, as the core load-bearing component in ball milling, is typically made of wear-resistant materials (such as agate and stainless steel) to withstand the intense impacts and friction generated by the high-speed movement of the grinding media during the milling process. It is mainly used to fill the precursor powder to be processed with the grinding media, commonly including wear-resistant grinding media such as cemented carbide balls and zirconia balls. The ball mill, through the high-speed rotation of the grinding jar or a planetary composite motion mode, drives the grinding media inside the jar to generate strong kinetic energy. Through repeated impacts, compression, and shearing of the precursor powder by the grinding media, the precursor powder transforms from an ordered crystalline or partially crystalline state into a disordered amorphous state, yielding a solid electrolyte powder precursor.

[0069] Ball milling time refers to the duration of ball mill operation for ball milling precursor powder, and is one of the key parameters for controlling the ball milling effect; ball milling speed refers to the rotational speed of the ball mill during operation (unit: rpm, revolutions per minute), that is, the number of rotations of the ball mill per minute, which directly affects the intensity of the grinding media's action on the precursor powder.

[0070] For example, the ball milling time can be any value between 2 and 30 hours, such as 2h, 6h, 10h, 14h, 19h, 22h, 25h, 28h, or 30h; the ball milling speed can be any value between 100 and 800 rpm, such as 100 rpm, 250 rpm, 400 rpm, 500 rpm, 650 rpm, 700 rpm, 750 rpm, or 800 rpm.

[0071] The amorphous solid electrolyte powder precursor obtained by amorphization treatment has a more uniform composition distribution and a structure that is more conducive to ion and electron conduction, which provides a basis for the subsequent preparation of halide solid electrolytes with both high electronic conductivity and excellent interfacial stability to cathode materials.

[0072] S103: Solid electrolyte powder precursors are sintered in an inert gas environment to obtain halide solid electrolytes with the molecular formula Li3TMX. 3+a , where a represents the average valence state of transition metal elements.

[0073] In this step, sintering is used to apply a specific temperature below the melting point to the solid electrolyte powder precursor obtained after amorphization treatment and hold it at that temperature for a certain period of time. Driven by thermal energy, a controllable crystallization reaction occurs, which promotes the diffusion and migration of atoms or ions between the solid electrolyte powder precursor particles. This causes the contact points between particles to gradually expand into grain boundaries, and the voids inside and between particles to continuously shrink, reduce, or even close, ultimately forming a halide solid electrolyte with a specific crystal structure, high density, and stable performance.

[0074] Similarly, in order to ensure that the halide solid electrolyte is not contaminated or deteriorated during the preparation process, the entire sintering process must be carried out in an inert gas environment, such as argon, neon, helium, nitrogen, etc.

[0075] In one possible implementation, the sintering time is 1 to 20 hours and / or the sintering temperature is 200 to 500°C.

[0076] Understandably, sintering temperature refers to the preset heating temperature during the sintering process, and sintering time refers to the duration for which the solid electrolyte powder precursor is kept heated at the preset sintering temperature, which determines the degree of densification of the solid electrolyte powder precursor. For example, the sintering time can be any value between 1 and 20 hours, such as 1h, 3h, 5h, 7h, 8h, 10h, 12h, 14h, 15h, 17h, 18h, or 20h; the sintering temperature can be any value between 200 and 500 degrees Celsius, such as 200℃, 270℃, 290℃, 310℃, 350℃, 380℃, 400℃, 440℃, 460℃, 480℃, or 500℃.

[0077] For example, sufficient neon gas is introduced into a sealed sintering furnace (such as a muffle furnace) or reaction vessel to completely purge the air. The solid electrolyte powder precursor is placed in a mold or crucible and then placed in a sintering device. Sintering is performed at a temperature of 400°C for 10 hours. During the sintering process, as the temperature increases, the amorphous structure in the solid electrolyte powder precursor powder crystallizes, forming a regularly arranged crystal structure, ultimately yielding a product with the molecular formula Li3TMX. 3+a The halide solid electrolyte, where a represents the average valence state of the transition metal element.

[0078] For example, if TM includes four transition metal elements: Ni, Co, Cr, and Fe, and X includes Cl, then TMCl bThe four transition metals, NiCl2, CrCl3, CoCl3, and FeCl3, have oxidation states of +2, +3, +3, and +3 respectively. Therefore, a = (2 + 3 + 3 + 3) / 4 = 2.75. If TM includes three transition metals, Mn, Ta, and Hf, and X includes Br, then TMBr b The three transition metals, MnBr5, TaBr4, and CrBr3, have valences of +5, +4, and +3 respectively, therefore a = (5 + 4 + 3) / 3 = 4; if TM includes five transition metals (Ti, Mn, V, Y, and Zr), and X includes I, then TMI b The five transition metal elements, including TiI3, MnI7, VI3, YI3, and ZrI4, have oxidation states of +3, +7, +3, +3, and +4, respectively. Therefore, a = (3 + 7 + 3 + 3 + 4) / 5 = 4.

[0079] As mentioned in S101, TM includes at least three transition metal elements. In other words, this application introduces at least three transition metal elements into the composition of the halide solid electrolyte, employs a high-entropy strategy to design the crystal structure and chemical composition of the halide solid electrolyte, and utilizes the uniform mixing of multiple transition metal elements at the atomic scale to effectively control the atomic arrangement and charge distribution in the halide solid electrolyte crystal, increasing the migration channels for lithium ions and electrons, reducing the transport energy barrier. Simultaneously, the synergistic effect of multiple transition metal elements can also enhance the structural stability and electrochemical compatibility of the halide solid electrolyte, reduce the occurrence of interfacial side reactions, and meet the high energy density application requirements of all-solid-state batteries.

[0080] The method for preparing halide solid electrolytes provided in this application mainly includes: firstly, in an inert gas environment, lithium halide LiX and halide TMX composed of at least three transition metal elements are reacted. b (The value of b is in the range of 2≤b≤7) The mixture is then used to obtain precursor powder. Subsequently, the precursor powder is subjected to amorphization treatment by methods such as mechanical ball milling to destroy its original crystal lattice and obtain a highly active amorphous solid electrolyte powder precursor. Finally, the solid electrolyte powder precursor is sintered in an inert gas environment to crystallize and densify it, ultimately yielding a product with the molecular formula Li3TMX. 3+a The halide solid electrolyte is prepared by the above method, where 'a' represents the average valence state of the transition metal element. The prepared halide solid electrolyte exhibits high ionic and electronic conductivity, significantly enhances interfacial and electrochemical stability of the cathode material, reduces polarization in all-solid-state batteries, lowers impedance, and improves the utilization rate of active materials, thus meeting the core application requirements of all-solid-state batteries in terms of high energy density, long cycle life, and high safety performance.

[0081] exist Figure 1 Based on the examples, the preparation method of this halide solid electrolyte further includes: weighing LiX and TMX at a molar ratio of 3:1. b .

[0082] For example, if TM includes Ti, Ni, and Cr, then LiX and TMX b The molar ratio of (TiX3, NiX2, CrX3) is 3:0.34:0.33:0.33; if TM includes Ti, Ni, Cr, and Co, then LiX and TMX b The molar ratio of (TiX3, NiX2, CrX3, CoX3) is 3:0.25:0.25:0.25:0.25; if TM includes Ti, Ni, Cr, Co, and Fe, then LiX and TMX b The molar ratio of (TiX3, NiX2, CrX3, CoX3, FeX3) is 3:0.2:0.2:0.2:0.2:0.2.

[0083] It should be noted that when the number of transition metal elements is 3, TMX b The molar ratio is evenly distributed among the three transition metal elements Ti, Ni, and Cr, namely TiX3, NiCl2, and CrCl3, each accounting for a certain percentage. In actual raw material weighing operations, it is impossible to achieve absolutely precise proportioning. To ensure that the total molar ratio of the three transition metal elements is 1, in this application, TiX3:NiCl2:CrCl3 = 0.34:0.33:0.33. That is, the relevant molar ratio values ​​in this paper have been approximated. This approximation method will not have a substantial impact on the preparation effect and performance of the final halide solid electrolyte. It is also applicable to other transition metal element combinations with similar indeterminate conditions, which will not be elaborated further below.

[0084] Furthermore, the above are merely illustrative examples. Given the diverse combinations of transition metal elements, it is impossible to exhaustively list all possible ratios. In practice, any three or more elements selected from Ti, Ni, Mn, Co, Fe, Cr, V, Y, Zr, Nb, Ta, Sc, Hf, and W can be used as the TM component, and LiX and the corresponding TMX can be weighed according to a 3:1 molar ratio. b The raw materials can all be used to prepare halide solid electrolytes that conform to the requirements of this application.

[0085] This application also provides an all-solid-state battery, comprising: the halide solid electrolyte mentioned in the above embodiments, or the halide solid electrolyte prepared by the method mentioned in the above method embodiments.

[0086] This all-solid-state battery can be used in vehicles, aircraft, drones, and also in power-consuming devices such as computers, mobile phones, digital cameras, and wearable devices, providing these devices with a stable and long-lasting power source and power support.

[0087] The following specific embodiments will provide a detailed description of the halide solid electrolyte and its preparation method provided in this application. Unless otherwise specified, the reagents, materials, and instruments used in the following embodiments are all conventional reagents, materials, and instruments in the art, and can all be obtained commercially. The reagents involved can also be synthesized by conventional methods in the art.

[0088] Example 1

[0089] This embodiment provides a halide solid electrolyte with the molecular formula Li3Ti. 0.34 Ni 0.33 Cr 0.33 Cl 5.67 Its preparation method includes the following steps:

[0090] 1) Weigh LiCl, TiCl3, NiCl2 and CrCl3 according to the molar ratio of 3:0.34:0.33:0.33, and place them in a mortar in a glove box filled with argon. Mix manually for 30 minutes to obtain precursor powder.

[0091] 2) The precursor powder was placed in a ball mill jar and sealed. It was then subjected to amorphous ball milling using a planetary ball mill (milling speed of 600 rpm and milling time of 24 h) to obtain a solid electrolyte powder precursor.

[0092] 3) The solid electrolyte powder precursor was sintered in an argon-filled muffle furnace (sintering temperature 400℃, sintering time 10h) to obtain Li3Ti. 0.34 Ni 0.33 Cr 0.33 Cl 5.67 Halogenated solid electrolyte (a=(2+3+3) / 3≈2.67).

[0093] Example 2

[0094] This embodiment provides a halide solid electrolyte with the molecular formula Li3Ti. 0.25 Ni 0.25 Cr 0.25 Co 0.25 Cl 5.75Its preparation method is basically the same as that mentioned in Example 1, except that:

[0095] In step 1): LiCl, TiCl3, NiCl2, CrCl3 and CoCl3 were weighed according to a molar ratio of 3:0.25:0.25:0.25:0.25 and placed in a mortar in a glove box filled with argon gas. They were manually mixed for 30 minutes to obtain precursor powder.

[0096] The final molecular formula obtained is Li3Ti 0.25 Ni 0.25 Cr 0.25 Co 0.25 Cl 5.75 The halide solid electrolyte (a=(3+2+3+3) / 4=2.75).

[0097] Example 3

[0098] This embodiment provides a halide solid electrolyte with the molecular formula Li3Ti. 0.2 Ni 0.2 Cr 0.2 Co 0.2 Fe 0.2 Cl 5.8 Its preparation method is basically the same as that mentioned in Example 1, except that:

[0099] In step 1): LiCl, TiCl3, NiCl2, CrCl3, CoCl3 and FeCl3 were weighed according to a molar ratio of 3:0.2:0.2:0.2:0.2 and placed in a mortar in a glove box filled with argon gas. They were manually mixed for 30 minutes to obtain precursor powder.

[0100] The final molecular formula obtained is Li3Ti 0.2 Ni 0.2 Cr 0.2 Co 0.2 Fe 0.2 Cl 5.8 Halogenated solid electrolyte (a=(3+2+3+3+3) / 5=2.8).

[0101] Example 4

[0102] This embodiment provides a halide solid electrolyte with the molecular formula Li3Ti. 0.2 Ni 0.2 Cr 0.2 Co 0.2 Mn 0.2 Cl 6.2Its preparation method is basically the same as that mentioned in Example 1, except that:

[0103] In step 1): LiCl, TiCl3, NiCl2, CrCl3, CoCl3 and MnCl5 were weighed according to a molar ratio of 3:0.2:0.2:0.2:0.2, and placed in a mortar in a glove box filled with argon gas. They were manually mixed for 30 minutes to obtain precursor powder.

[0104] The final molecular formula obtained is Li3Ti 0.2 Ni 0.2 Cr 0.2 Co 0.2 Mn 0.2 Cl 6.2 Halogenated solid electrolyte (a=(3+2+3+3+5) / 5=3.2).

[0105] Example 5

[0106] This embodiment provides a halide solid electrolyte with the molecular formula Li3Ti. 0.2 Ni 0.2 Cr 0.2 Co 0.2 Fe 0.2 Cl 2.8 Br3 is prepared in a manner that is basically the same as the preparation method mentioned in Example 1, except that:

[0107] In step 1): LiBr, TiCl3, NiCl2, CrCl3, CoCl3 and FeCl3 were weighed according to a molar ratio of 3:0.2:0.2:0.2:0.2 and placed in a mortar in a glove box filled with argon gas. They were manually mixed for 30 minutes to obtain precursor powder.

[0108] The final molecular formula obtained is Li3Ti 0.2 Ni 0.2 Cr 0.2 Co 0.2 Fe 0.2 Cl 2.8 Br3 halide solid electrolyte (a=(3+2+3+3+3) / 5=2.8).

[0109] Example 6

[0110] This embodiment provides a halide solid electrolyte with the molecular formula Li3Ti. 0.2 Ni 0.2 Cr 0.2 Co 0.2 Fe 0.2Br 5.8 Its preparation method is basically the same as that mentioned in Example 1, except that:

[0111] In step 1): LiBr, TiBr3, NiBr2, CrBr3, CoBr3 and FeBr3 were weighed according to a molar ratio of 3:0.2:0.2:0.2:0.2 and placed in a mortar in a glove box filled with argon gas. They were manually mixed for 30 minutes to obtain precursor powder.

[0112] The final molecular formula obtained is Li3Ti 0.2 Ni 0.2 Cr 0.2 Co 0.2 Fe 0.2 Br 5.8 Halogenated solid electrolyte (a=(3+2+3+3+3) / 5=2.8).

[0113] Example 7

[0114] This embodiment provides a halide solid electrolyte with the molecular formula Li3Ti. 0.2 Ni 0.2 Cr 0.2 Co 0.2 V 0.2 Cl 5.2 F 0.6 Its preparation method is basically the same as that mentioned in Example 1, except that:

[0115] In step 1): LiCl, TiCl3, NiCl2, CrCl3, CoCl3 and VF3 were weighed according to a molar ratio of 3:0.2:0.2:0.2:0.2 and placed in a mortar in a glove box filled with argon gas. They were manually mixed for 30 minutes to obtain precursor powder.

[0116] The final molecular formula obtained is Li3Ti 0.2 Ni 0.2 Cr 0.2 Co 0.2 V 0.2 Cl 5.2 F 0.6 Halogenated solid electrolyte (a=(3+2+3+3+3) / 5=2.8).

[0117] Comparative Example

[0118] This embodiment provides a halide solid electrolyte with the molecular formula Li3TiCl6. Its preparation method is basically the same as that mentioned in Example 1, except that in step 1): LiCl and TiCl3 are weighed at a molar ratio of 3:1 and placed in a mortar in an argon-filled glove box. The mixture is manually mixed for 30 minutes to obtain precursor powder. Finally, a halide solid electrolyte with the molecular formula Li3TiCl6 is obtained.

[0119] Test Example 1

[0120] Ionic conductivity test: 100 mg of halide solid electrolyte was weighed and placed in a mold. A pressure of 360 MPa was applied to press it into an electrolyte sheet with a diameter of 10 mm. Under pressure, the impedance value of the halide solid electrolyte was measured using an electrochemical workstation at room temperature (25 °C) using the electrochemical impedance spectroscopy method. The real part of the minimum absolute value of multiple impedance phase angles was taken as the effective impedance value R. SE Using this effective impedance value, the ionic conductivity of the halide solid electrolyte is calculated. The calculation formula is: ,in, R represents the ionic conductivity (unit: mS / cm), L represents the thickness of the electrolyte sheet (unit: cm), and R represents the electrolyte thickness. SE The effective impedance value of the halide solid electrolyte obtained by electrochemical impedance spectroscopy (unit: Ω) is represented by S, which represents the cross-sectional area of ​​the electrolyte sheet (unit: cm²). 2 The test results of ionic conductivity are shown in Table 1.

[0121] Test Example 2

[0122] Electronic conductivity test: 100 mg of halide solid electrolyte was weighed and placed in a mold. A pressure of 360 MPa was applied to press it into an electrolyte sheet with a diameter of 10 mm. Under pressure, the electrolyte was measured using a DC polarization method at room temperature (25 °C) using an electrochemical workstation (test time 60 min). The real part of the minimum absolute value of multiple impedance phase angles was taken as the effective impedance value R. SE Using this effective impedance value, the electronic conductivity of the halide solid electrolyte is calculated. The calculation formula is: ,in, The value represents electronic conductivity (unit: mS / cm). The test results for electronic conductivity are shown in Table 2.

[0123] Test Example 3

[0124] Electrochemical window testing: A halide solid electrolyte and conductive carbon powder were weighed at a mass ratio of 70:30 and ground uniformly using an agate mortar to obtain a halide solid electrolyte-conductive carbon powder mixture. In an insulating outer cylinder with a diameter of 10 mm, 20 mg of the halide solid electrolyte-conductive carbon powder mixture and 20 mg of Li were... 5.4 PS 4.4 Cl 1.6 The electrolytes are layered and then pressurized to form a solid mass at 360 MPa. Next, in Li... 5.4 PS 4.4 Cl 1.6 A lithium foil was stacked on the side of the electrolyte and pressurized to 100 MPa. Stainless steel current collectors were then placed above and below the stack, with current collection leads attached to them. Linear scanning voltammetry was performed, with a scan range of 2–5 V and a scan rate of 0.1 mV / s. The oxidation potential of the halide solid electrolyte was determined by plotting a tangent to the oxidation peak of the test curve and finding its intersection with the abscissa. The electrochemical window test results are shown in Table 3.

[0125] Test Example 4

[0126] Battery cycle performance test: The halide solid electrolyte and the positive electrode active material lithium-rich manganese-based xLi2MnO3 were obtained by weighing at a mass ratio of 20:80. (1-x)LiMO2 was ground uniformly using an agate mortar in an argon-filled glove box to prepare a composite cathode material. Then, 14 mg of the composite cathode material and 70 mg of a halide solid electrolyte were stacked in an insulating outer cylinder with a diameter of 10 mm. This was pressurized at 360 MPa to form the cathode and solid electrolyte layer. Next, an aluminum foil was stacked on the cathode side to form a current collector. Then, on the opposite side of the solid electrolyte layer in contact with the cathode, a lithium sheet with a thickness of 200 μm and a diameter of 10 mm was placed as the anode material, and pressurized at 80 MPa to obtain a laminate (all-solid-state battery) consisting of a cathode, a solid electrolyte layer, and a anode. Finally, stainless steel current collectors were placed on the top and bottom of the laminate, and current collector leads were attached to the current collectors. Cycle performance tests were conducted on the assembled all-solid-state battery under the following conditions: current density of 1C and voltage range of 2.7~4.3V (Li). + / Li). The battery cycle performance test results are shown in Table 4.

[0127] Table 1. Test results of ionic conductivity

[0128]

[0129] Based on Table 1, the following conclusions can be drawn:

[0130] The ionic conductivity of Examples 1 to 7 (all referring to the ionic conductivity / electronic conductivity / oxidation potential / first-efficiency / capacity retention after 200 cycles corresponding to the halide solid electrolytes provided in the examples, which will not be repeated below) is between 1.29 mS / cm and 2.32 mS / cm, with an average ionic conductivity of 1.79 mS / cm. These are all much higher than those of Li3TiCl6 without multiple transition metal elements in the comparative examples (ionic conductivity of only 0.92 mS / cm), showing superior ionic conductivity. This indicates that the technical solution of introducing multiple transition metal elements based on the high-entropy strategy provided in this application can effectively improve the ion transport performance of halide solid electrolytes.

[0131] Table 2 Test results of electronic conductivity

[0132]

[0133] Based on Table 2, the following conclusions can be drawn:

[0134] The electronic conductivity of Examples 1 to 7 is 48 × 10⁻⁶. -6 mS / cm ~850×10 -6 Between mS / cm, the average electronic conductivity can reach 505 × 10⁻⁶ mS / cm. -6 The mS / cm values ​​are all significantly higher than those of Li3TiCl6 (with an electronic conductivity of only 0.61 × 10⁻⁶) in the comparative example, which is not doped with multiple transition metal elements. -6 (mS / cm), exhibiting superior electronic conductivity, and the electronic conductivity of Examples 1 to 7 is around 10. -6 The low electronic conductivity of mS / cm meets the basic application requirements of electronic insulation for all-solid-state batteries, indicating that the halide solid electrolyte provided in this application has excellent electronic conductivity and achieves a good balance between ion transport performance and electronic insulation performance.

[0135] Table 3 Test results of the electrochemical window

[0136]

[0137] Based on Table 3, the following conclusions can be drawn:

[0138] The oxidation potentials of Examples 1 to 7 range from 4.17V to 4.71V, with an average oxidation potential of 4.54V. These values ​​are significantly higher than those of Li3TiCl6 (oxidation potential of only 3.96V) in the comparative examples, which are not doped with multiple transition metal elements. This indicates that the halide solid electrolyte provided in this application has a large electrochemical window and exhibits excellent oxidation stability / electrochemical stability under high voltage conditions at the cathode, making it better suited to the application requirements of high-voltage cathode materials.

[0139] Table 4 Battery Cycle Performance Test Results

[0140]

[0141] Understandably, first-cycle efficiency (CEE) refers to the percentage of discharge capacity to charge capacity in the first cycle of an all-solid-state battery. The calculation formula is: CEE = First charge capacity / First discharge capacity × 100%. It is used to reflect the degree of energy loss during the first cycle of the battery. The higher the CEE, the smaller the irreversible capacity loss caused by interfacial side reactions, electrolyte decomposition, etc. during the initial charge and discharge process, and the higher the energy conversion efficiency.

[0142] The 200-cycle capacity retention rate refers to the percentage of the discharge capacity on the 200th charge-discharge cycle to the initial discharge capacity after 200 charge-discharge cycles for an all-solid-state battery. The calculation formula is: 200-cycle capacity retention rate = initial discharge capacity / 200th discharge capacity × 100%. It is used to measure the cycle stability of the battery. The higher the capacity retention rate, the better the integrity of the electrode structure, the interfacial compatibility between the electrolyte and the electrode, and the utilization rate of the active materials during multiple cycles, and the more guaranteed the battery's lifespan.

[0143] Based on Table 4, the following conclusions can be drawn:

[0144] The initial efficiency and capacity retention after 200 cycles of Examples 1 to 7 were 86.50%~93.2% and 77.90%~91.30%, respectively, with average initial efficiency and average capacity retention after 200 cycles reaching 89.54% and 87.01%, respectively. These figures are significantly higher than those of Li3TiCl6 in the comparative examples, which did not have multiple transition metal elements doped (initial efficiency was only 75.10% and capacity retention after 200 cycles was only 61.60%). This indicates that the all-solid-state battery, including the halide electrolyte provided in this application, has good interfacial compatibility between the halide solid electrolyte and the cathode material, excellent utilization of active materials, and high energy conversion efficiency.

[0145] In summary, the halide solid electrolyte, its preparation method, and the all-solid-state battery provided in this application can effectively improve the ionic and electronic conductivity of the halide solid electrolyte, enhance the electrochemical stability and interfacial stability of the halide electrolyte to the cathode material, reduce the polarization of the all-solid-state battery, lower the impedance of the all-solid-state battery, and improve the utilization rate of active materials, thereby improving the energy density and performance of the all-solid-state battery and significantly extending its cycle life.

[0146] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A halide solid electrolyte, characterized in that, The molecular formula of the halide solid electrolyte is Li3TMX. 3+a ; Wherein, TM represents a transition metal element, X represents a halogen element, TM includes at least three transition metal elements, and a represents the average valence state of the transition metal element.

2. The halide solid electrolyte according to claim 1, characterized in that, The TM includes at least three of the following elements: Ti, Ni, Mn, Co, Fe, Cr, V, Y, Zr, Nb, Ta, Sc, Hf and W.

3. The halide solid electrolyte according to claim 1 or 2, characterized in that, The X includes at least one of the following elements: F, Cl, Br, and I.

4. A method for preparing a halide solid electrolyte, characterized in that, include: LiX and TMX b The mixture is mixed in an inert gas environment to obtain a precursor powder, wherein TM represents a transition metal element, X represents a halogen element, and the value of b ranges from 2 to b to 7. The TM includes at least three transition metal elements. The precursor powder is subjected to amorphization treatment to obtain a solid electrolyte powder precursor; The solid electrolyte powder precursor is sintered in an inert gas environment to obtain a halide solid electrolyte, wherein the molecular formula of the halide solid electrolyte is Li3TMX. 3+a , where 'a' represents the average valence state of the transition metal element.

5. The method according to claim 4, characterized in that, The TM includes at least three of the following elements: Ti, Ni, Mn, Co, Fe, Cr, V, Y, Zr, Nb, Ta, Sc, Hf and W; And / or, The X includes at least one of the following elements: F, Cl, Br, and I.

6. The method according to claim 4 or 5, characterized in that, The method further includes: The LiX and TMX were obtained by weighing at a molar ratio of 3:

1. b .

7. The method according to claim 4 or 5, characterized in that, The process of amorphizing the precursor powder to obtain a solid electrolyte powder precursor includes: The precursor powder is placed in a ball mill jar and ball milled to obtain the solid electrolyte powder precursor.

8. The method according to claim 7, characterized in that, When performing ball milling, the milling time is 2 to 30 hours, and / or the milling speed is 100 to 800 rpm.

9. The method according to claim 4 or 5, characterized in that, During sintering, the sintering time is 1 to 20 hours, and / or the sintering temperature is 200 to 500°C.

10. An all-solid-state battery, characterized in that, Includes the halide solid electrolyte according to any one of claims 1 to 3, or the halide solid electrolyte prepared by the method according to any one of claims 4 to 9.

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