A solid electrolyte, a preparation method thereof, and a solid-state lithium battery

Abstract

This application belongs to the technical field of lithium batteries, and particularly relates to a solid electrolyte, a preparation method thereof, and a solid-state lithium battery. The solid electrolyte includes an amorphous non-crystalline halide electrolyte, an oxide solid electrolyte, and a tantalum-containing interface layer. The amorphous non-crystalline halide electrolyte coats the oxide solid electrolyte, and the tantalum-containing interface layer coats the surface of the solid electrolyte; the molecular formula of the solid electrolyte is TaM5-Li a X b Y c OCl@LLNO; wherein, Li a X b Y c OCl is an amorphous non-crystalline halide electrolyte, LLNO is an oxide solid electrolyte, TaM5 is a tantalum-containing interface layer, M is iodine or fluorine, X is a first metal element, Y is a second metal element, N is zirconium and / or titanium, 1≦a≦2, 0≦b≦5, 0≦c≦5, and at least one of the values of b and c is greater than 0; since when the amorphous non-crystalline halide electrolyte is synthesized with the oxide solid electrolyte, the by-product HCl gas will remove the impurity phase on the surface of the solid electrolyte, reducing the interfacial impedance of the oxide solid electrolyte.

Description

Technical Field

[0001] This application belongs to the technical field of lithium batteries, and particularly relates to a solid electrolyte, a preparation method thereof, and a solid-state lithium battery. Background Art

[0002] At present, in all-solid-state batteries (ASSB, All-Solid-State Battery), the oxide electrolyte particles have high mechanical strength and hardness, resulting in very poor interfacial contact with the electrodes, and there is lithium dendrite growth, leading to a relatively high interfacial impedance. The existing technology reduces the interfacial impedance by adding polymers to artificially form a solid electrolyte interface (SEI, Solid Electrolyte Interface) and other means, resulting in low efficiency of high-rate charge and discharge of all-solid-state batteries; reducing the charge and discharge efficiency of all-solid-state batteries and the user experience.

[0003] The existing solid electrolytes have problems such as poor contact, lithium dendrite growth, high interfacial impedance with the electrodes, and low Coulomb efficiency. Summary of the Invention

[0004] This application provides a solid electrolyte, a preparation method thereof, and a solid-state lithium battery, aiming to solve to a certain extent the problems of poor contact of the solid electrolyte, lithium dendrite growth, high interfacial impedance with the electrodes, and low Coulomb efficiency.

[0005] In a first aspect, this application provides a solid electrolyte, which includes an amorphous non-crystalline halide electrolyte, an oxide solid electrolyte, and a tantalum-containing interface layer. The amorphous non-crystalline halide electrolyte coats the oxide solid electrolyte, and the tantalum-containing interface layer coats the surface of the solid electrolyte; the molecular formula of the solid electrolyte is TaM5-Li a X b Y c OCl@LLNO;

[0006] Among them, Li a X b Y c OCl is an amorphous non-crystalline halide electrolyte, LLNO is an oxide solid electrolyte, TaM5 is the tantalum-containing interface layer, M is iodine or fluorine, X is a first metal element, the first metal element is derived from the raw material metal halide salt, Y is a second metal element, the second metal element is derived from the raw material polymeric metal halide salt, N is zirconium and / or titanium, 1≦a≦2, 0≦b≦5, 0≦c≦5, and at least one of the values of b and c is greater than 0.

[0007] In one embodiment, the first metal element includes one or more of aluminum, calcium, chromium, gallium, zinc, magnesium, and tungsten;

[0008] The second metal element includes one or more of aluminum, calcium, chromium, copper, cobalt, tin, rhodium, vanadium, and iron;

[0009] If the first metal element is the same as the second metal element, the value of b or c is 0.

[0010] In one embodiment, the oxide solid electrolyte includes a composition of one or more of lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, and lithium lanthanum zirconium titanium oxide;

[0011] The metal halide salt includes a composition of one or more of AlCl3, CaCl2, CrCl5, GaCl3, ZnCl2, MgCl2, and WCl5;

[0012] The polymeric metal halide salt includes a composition of one or more of AlCl3·nH2O, CaCl2·nH2O, CrCl2·nH2O, CuCl2·nH2O, CoCl2·nH2O, SnCl2·nH2O, RhCl2·nH2O, VCl2·nH2O, and FeCl2·nH2O, where 1 ≤ n ≤ 6.

[0013] In a second aspect, the present application provides a method for preparing a solid electrolyte as described in any one of the first aspect, including:

[0014] Mix lithium chloride, the metal halide salt, and the polymeric metal halide salt according to a preset molar ratio, and add the obtained halogenated mixture to a ball milling tank for ball milling;

[0015] During the ball milling process, add the oxide solid electrolyte in multiple portions at a first preset interval until the mass ratio of the oxide solid electrolyte to the halogenated mixture reaches a preset mass ratio, and the mass of each added oxide solid electrolyte is 5% - 15% of the mass of the halogenated mixture;

[0016] During the continued ball milling process, pause the ball milling every second preset interval, and keep the ball milling tank at a preset temperature in an inert gas atmosphere to obtain electrolyte powder;

[0017] Press the electrolyte powder into a shape to obtain an electrolyte;

[0018] Etch the electrolyte to a preset depth;

[0019] Sinter the etched electrolyte and a water-absorbing molecular sieve in a tantalum vapor atmosphere in a tubular furnace to obtain a solid electrolyte with an amorphous non-crystalline phase halide electrolyte coating the oxide solid electrolyte.

[0020] In one embodiment, the preset molar ratio of the lithium chloride, the metal halide salt, and the polymeric metal halide salt is (1 to 10) : (1 to 20) : 1;

[0021] The ball-to-material ratio of the ball milling is (10 to 40) : 1, the ball milling time is 20 min to 2400 min, and the ball milling rate is 1 r / min to 1000 r / min.

[0022] In one embodiment, the first preset interval time is 10 min to 30 min;

[0023] The preset mass ratio of the oxide solid electrolyte to the halogenated mixture is 10 : (0.1 to 5);

[0024] The D50 of the oxide solid electrolyte is 700 nm to 1500 nm.

[0025] In one embodiment, the second preset interval time is 5 min to 10 min;

[0026] The preset temperature is 100 °C to 300 °C, and the heat preservation time of the inert gas heat preservation is 10 min to 60 min.

[0027] In one embodiment, the preset depth is 3 nm to 7 nm.

[0028] In one embodiment, the tantalum-containing vapor includes tantalum pentaiodide vapor or tantalum pentafluoride vapor;

[0029] The parameters of the sintering are: the sintering temperature is 400 °C to 1200 °C, and the sintering time is 2 h to 24 h.

[0030] In a third aspect, the present application provides a solid-state lithium battery, including the solid electrolyte according to any one of the contents in the first aspect, or the solid electrolyte obtained by the preparation method of the solid electrolyte sheet according to any one of the contents in the second aspect.

[0031] The beneficial effects of the present application compared with the prior art are:

[0032] In the solid electrolyte provided by the present application, an amorphous amorphous-phase halide electrolyte coats the oxide solid electrolyte, and a tantalum-containing interface layer coats the surface of the solid electrolyte; the molecular formula of the solid electrolyte is TaM5-Li a X b Y c OCl@LLNO; wherein, Li a X b Y cOCl is an amorphous halide electrolyte, LLNO is an oxide solid electrolyte, TaM5 is a tantalum-containing interface layer, M is iodine or fluorine, X is a first metal element, the first metal element is derived from the raw material metal halide salt, Y is a second metal element, the second metal element is derived from the raw material polymeric metal halide salt, N is zirconium and / or titanium, 1 ≦ a ≦ 2, 0 ≦ b ≦ 5, 0 ≦ c ≦ 5, and at least one of the values of b and c is greater than 0; when the amorphous halide electrolyte is synthesized with the oxide solid electrolyte, the by-product HCl gas can remove the impurity phases (such as Li2CO3, LiOH, Li2O) on the surface of the oxide solid electrolyte, exposing the lithiumophilic phase, improving the compatibility between the oxide solid electrolyte and the polymer electrolyte / binder, thereby reducing the interfacial impedance of the oxide solid electrolyte and improving the Coulombic efficiency of the solid-state battery; when lithium dendrites grow along the tantalum-containing interface layer of the oxide solid electrolyte, the amorphous halide electrolyte will react with the lithium dendrites, consuming the lithium dendrites to form a self-healing phenomenon, preventing the formation of dead lithium by lithium ions, further improving the Coulombic efficiency, and also improving the safety of the solid-state battery. Brief Description of the Drawings

[0033] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0034] Figure 1 It is a schematic structural diagram of a solid electrolyte provided by an embodiment of the present application;

[0035] Figure 2 It is a particle element distribution diagram after ball milling of the halogenated mixture of the amorphous halide electrolyte raw material in step 2 of Embodiment 1 of the present application and the oxide solid electrolyte;

[0036] Figure 3 It is the amorphous halide electrolyte LiAl 1.5 OCl 3.5 (abbreviated as LAOC) and the oxide solid electrolyte LLZO react together and the comparison schematic diagram of the HCl concentration of the HCl generated by reacting alone with only LAOC;

[0037] Figure 4 It is a comparison schematic diagram of the electrolyte impedance of the co-ball milling synthesis reaction of LAOC and LLZO in Embodiment 1 of the present application and the electrolyte impedance of the initial particles of LLZO;

[0038] Figure 5Schematic diagram of the impedance of the solid electrolytes prepared by using tantalum pentaiodide vapor in Example 1 of the present application and using argon gas of an inert gas atmosphere without using tantalum pentaiodide vapor in Comparative Example 8 respectively;

[0039] Figure 6 Schematic diagram of the cycle of the Li / SE / Li symmetric battery assembled with the solid electrolytes prepared in Example 1, Comparative Example 8, and Comparative Example 9 of the present application;

[0040] Figure 7 Schematic diagram of the comparison of the capacity retention rates of the all-solid-state batteries assembled with the solid electrolyte sheets prepared in Example 2 of the present application and Comparative Example 6 respectively. Detailed implementation manners

[0041] In order to make the technical problems to be solved, technical solutions and beneficial effects of the present application clearer and more understandable, the present application will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0042] In the present application, the term "and / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0043] In the present application, "at least one" means one or more, and "a plurality" means two or more. "At least one (item)" or similar expressions thereof refer to any combination of these items, including any combination of single item (item) or plural items (items). For example, "at least one (item) of a, b, or c", or, "at least one (item) of a, b, and c" can both represent: a, b, c, a~b (that is, a and b), a~c, b~c, or a~b~c, where a, b, and c can be single or multiple respectively.

[0044] The terms "first" and "second" are only used for descriptive purposes to distinguish objects such as substances from each other, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX can also be called the second XX, and similarly, the second XX can also be called the first XX. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0045] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "the" and "said" used in the embodiments of the present application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0046] It should be understood that in various embodiments of the present application, the sequence numbers of the various processes do not mean the order of execution, and some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0047] The weights of the relevant components mentioned in the specification of the embodiments of the present application not only can refer to the specific contents of each component, but also can represent the proportional relationship of the weights between the components. Therefore, as long as the contents of the relevant components in the specification of the embodiments of the present application are enlarged or reduced in proportion, they are within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass mentioned in the specification of the embodiments of the present application can be mass units well-known in the chemical industry such as μg, mg, g, kg, etc.

[0048] Unless otherwise defined, all the technical terms used hereinafter have the same meanings as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0049] Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the present application can be obtained through the market or can be prepared by existing methods.

[0050] At present, as an electrochemical energy storage device, lithium-ion batteries have achieved great development and wide application, and lithium-ion batteries play an important role in powering portable electronic devices.

[0051] However, lithium-ion batteries still have prominent safety problems in their inherent flammability and potential thermal runaway, especially when exposed to high temperatures or physical damage. In addition, due to the growing demand for large-scale energy storage solutions, especially the technical solutions of integrating renewable energy and using electric drive in electric vehicles, the demand for batteries with higher energy density, higher safety and more sustainable materials has increased. The lithium-ion batteries of the prior art cannot meet the requirements of scenario development in terms of energy density and other aspects.

[0052] As a new generation of battery technology, all-solid-state batteries (ASSB, All-Solid-State Battery) have many advantages over traditional lithium-ion batteries, such as electrochemical energy storage and power supply, and also include higher safety, higher energy density, higher thermal stability and longer service life.

[0053] However, currently, the oxide electrolyte particles in all-solid-state batteries have high mechanical strength and hardness, resulting in very poor interfacial contact with the electrodes, and there is lithium dendrite growth, leading to a relatively high interfacial impedance. The existing technology reduces the interfacial impedance by means such as adding polymers to artificially form a solid electrolyte interface (SEI, Solid Electrolyte Interface), resulting in low efficiency of high-rate charge and discharge of all-solid-state batteries; the charge and discharge efficiency of all-solid-state batteries is reduced, and the user experience is degraded.

[0054] To solve the above problems to a certain extent, a first aspect of the present application provides a solid electrolyte, such as Figure 1 shown, the solid electrolyte includes an amorphous halide electrolyte, an oxide solid electrolyte, and a tantalum-containing interface layer. The amorphous halide electrolyte coats the oxide solid electrolyte, and the tantalum-containing interface layer 2 coats the surface of the solid electrolyte 1; the molecular formula of the solid electrolyte is TaM5-Li a X b Y c OCl@LLNO; wherein, the enlarged view is a schematic diagram of the amorphous halide electrolyte coating the oxide solid electrolyte, and Li a X b Y c OCl is the amorphous halide electrolyte, LLNO is the oxide solid electrolyte, TaM5 is the tantalum-containing interface layer, M is iodine or fluorine, X is the first metal element, the first metal element is derived from the raw material metal halide salt, Y is the second metal element, the first metal element is derived from the raw material polymeric metal halide salt, N is zirconium and / or titanium, 1≦a≦2, 0≦b≦5, 0≦c≦5, and at least one of the values of b and c is greater than 0.

[0055] In this embodiment, when the amorphous and non-crystalline halide electrolyte is synthesized with the oxide solid electrolyte, the by-product HCl gas can remove the impurity phases (such as Li2CO3, LiOH, Li2O) on the surface of the oxide solid electrolyte, exposing the lithiumophilic phase, improving the compatibility between the oxide solid electrolyte and the polymer electrolyte / binder, thereby reducing the interfacial impedance of the oxide solid electrolyte, enabling high-rate charge and discharge, and improving the Coulomb efficiency of the solid-state battery. When lithium dendrites grow along the tantalum-containing interface layer of the oxide solid electrolyte, the amorphous and non-crystalline halide electrolyte will react with the lithium dendrites, consuming the lithium dendrites to form a self-healing phenomenon, preventing the formation of dead lithium from lithium ions, further improving the Coulomb efficiency, and also improving the safety of the solid-state battery. Additionally, without affecting the ionic conductivity of the oxide solid electrolyte, the tantalum-containing interface layer performs secondary coating on the oxide solid electrolyte, avoiding the reaction between the halide electrolyte coating layer and the lithium metal negative electrode, obtaining an interface phase that is doubly stable to the positive and negative electrodes, improving the stability of the lithium metal negative electrode, and further improving the safety of the solid-state battery.

[0056] In one embodiment, the metal halide salt includes a composition of one or more of AlCl3, CaCl2, CrCl5, GaCl3, ZnCl2, MgCl2, and WCl5; the first metal element includes one or more of aluminum, calcium, chromium, gallium, zinc, magnesium, and tungsten; the metal halide salt can be coated on the grain boundaries of the oxide solid electrolyte in an amorphous form, blocking electron migration without affecting ion transport and inhibiting the growth of lithium dendrites.

[0057] In one embodiment, the polymeric metal halide salt includes a composition of one or more of AlCl3·nH2O, CaCl2·nH2O, CrCl2·nH2O, CuCl2·nH2O, CoCl2·nH2O, SnCl2·nH2O, RhCl2·nH2O, VCl2·nH2O, and FeCl2·nH2O, where 1 ≤ n ≤ 6; the second metal element includes one or more of aluminum, calcium, chromium, copper, cobalt, tin, rhodium, vanadium, and iron. If the first metal element is the same as the second metal element, Li a X b Y c The value of b or c in OCl is 0. For example, if both the first metal element and the second metal element are Al, then Li a X b Y c OCl is represented as Li a Al b OCl or Li a Al cOCl; The polymeric metal halide salt can coat the grain boundaries of the oxide solid electrolyte in an amorphous form, block electron migration without affecting ion transport, and inhibit the growth of lithium dendrites. In addition, the polymeric metal halide salt will hydrolyze and generate HCl gas, which can remove the heterogeneous phases (such as Li2CO3, LiOH, Li2O) on the surface of the oxide solid electrolyte, expose the lithiumophilic phase, improve the compatibility between the oxide solid electrolyte and the polymer electrolyte / binder, thereby reducing the interfacial impedance of the oxide solid electrolyte and improving the Coulombic efficiency of the solid-state battery.

[0058] In one embodiment, N is zirconium and titanium, is zirconium, or is titanium, that is, the oxide solid electrolyte LLNO includes a composition of one or more of lithium lanthanum zirconium oxide (LLZO), lithium lanthanum titanium oxide (LLTO), and lithium lanthanum zirconium titanium oxide (LLZTO); the oxide solid electrolyte in this embodiment has a high ionic conductivity (reaching the 10 -3 S / cm level) and high chemical and electrochemical stability with the lithium metal negative electrode.

[0059] In a second aspect, the present application provides a method for preparing a solid electrolyte as described in any one of the content of the first aspect, including:

[0060] S10, mixing lithium chloride, metal halide salt, and polymeric metal halide salt according to a preset molar ratio, and adding the obtained halogenated mixture to a ball mill for ball milling.

[0061] S20, during the ball milling process, add the oxide solid electrolyte in multiple portions at a first preset interval time until the mass ratio of the oxide solid electrolyte to the halogenated mixture reaches a preset mass ratio, and the mass of the oxide solid electrolyte added each time is 5% - 15% of the mass of the halogenated mixture.

[0062] S30, during the continued ball milling process, pause the ball milling every second preset interval time, and keep the ball mill at a preset temperature in an inert gas atmosphere to obtain electrolyte powder.

[0063] S40, press the electrolyte powder into a mold to obtain an electrolyte.

[0064] S50, etch the electrolyte to a preset depth.

[0065] S60, sinter the etched electrolyte and the water-absorbing molecular sieve in a tantalum vapor atmosphere in a tubular furnace to obtain a solid electrolyte with an amorphous non-crystalline phase halide electrolyte coating the oxide solid electrolyte.

[0066] The solid electrolyte particles obtained by the prior art preparation method have high mechanical strength and hardness, and LiOH is easily generated in the oil-based solvent for the oxide solid electrolyte, and LiOH will cause the binder / polymer to denature. Therefore, the oxide solid electrolyte is not suitable as an inorganic filler for polymers; this results in very poor interfacial contact between the solid electrolyte and the electrode, leading to a high interfacial impedance. In addition, the preparation method of the solid electrolyte in the prior art uses complex hot pressing and sintering methods to prepare the electrolyte layer, increasing the manufacturing cost.

[0067] For the solid electrolyte obtained by the preparation method of the solid electrolyte in this embodiment, since the amorphous halide electrolyte Li a X b Y c OCl, when ball-milling and vacuum heating and holding with the oxide solid electrolyte for synthesis, the polymeric metal halide salt will hydrolyze and react to generate HCl gas. The by-product HCl gas will remove the impurity phases (such as Li2CO3, LiOH, Li2O) on the surface of the oxide solid electrolyte, exposing the lithiophilic phase, improving the compatibility between the oxide solid electrolyte and the polymer electrolyte / binder, thereby reducing the interfacial impedance of the oxide solid electrolyte, enabling high-rate charge and discharge, and improving the Coulomb efficiency of the solid-state battery; when lithium dendrites grow along the tantalum-containing interface layer of the oxide solid electrolyte, the amorphous halide electrolyte will react with the lithium dendrites to consume the lithium dendrites to form a self-healing phenomenon, avoiding the formation of dead lithium by lithium ions, further improving the Coulomb efficiency, and also improving the safety of the solid-state battery. In addition, without affecting the ionic conductivity of the oxide solid electrolyte, the tantalum-containing interface layer performs a surface treatment of secondary coating on the oxide solid electrolyte, avoiding the reaction between the halide electrolyte coating layer and the lithium metal negative electrode, obtaining an interface phase that is double-stable to the positive and negative electrodes, improving the stability of the lithium metal negative electrode, and further improving the safety of the solid-state battery. At the same time, in this embodiment, the cold pressing method is used to prepare the electrolyte layer, and the polymeric metal halide salt with crystal water is used to introduce oxygen atoms, without using battery-grade raw materials, further reducing the cost of the solid-state battery.

[0068] In one embodiment, the shape of the solid electrolyte is sheet-like or cake-like. Among them, the thickness of the solid electrolyte is 20 μm to 150 μm. Since the ionic conductivity of the amorphous halide electrolyte Li a X b Y c OCl is also at the 10 -3 S / cm level, and at the same time, the texture is relatively soft. When pressed into shape, it can fill the gaps between the oxide solid electrolyte particles, improve the compaction density, and form a sheet-like or cake-like solid electrolyte with few voids and high density, thereby improving the energy density of the solid-state battery.

[0069] In one embodiment, the preset molar ratio of lithium chloride, metal halide salt, and polymeric metal halide salt is (1 to 10)﹕(1 to 20)﹕1; adopting the molar ratio range of this embodiment can avoid generating more HCl gas, reduce the treatment cost; and can also maintain the balance between lithium and metal salt, improving the ionic conductivity of the solid-state battery.

[0070] In one embodiment, the ball-to-material ratio of ball milling is (10 to 40)﹕1, the ball milling time is 20 min to 2400 min, and the ball milling rate is 1 r / min to 1000 r / min; adopting the ball milling parameters of this embodiment can better mix the halide electrolyte and the oxide solid electrolyte and obtain a particle size that meets the requirements.

[0071] In one embodiment, the first preset interval time is 10 min to 30 min; the preset mass ratio of the oxide solid electrolyte to the halide mixture is 10﹕(0.1 to 5); the D50 of the oxide solid electrolyte is 700 nm to 1500 nm; adopting the first preset interval time of this embodiment can better mix the halide electrolyte and the oxide solid electrolyte, improving the coating rate; and the mass of the oxide solid electrolyte is greater than the mass of the halide mixture, ensuring the electrochemical performance of the solid-state battery; maintaining the D50 particle size of the oxide solid electrolyte can increase the contact area, thereby reducing the interfacial impedance.

[0072] In one embodiment, the second preset interval time is 5 min to 10 min; the preset temperature is 100℃ to 300℃, and the heat preservation time of inert gas heat preservation is 10 min to 60 min; adopting the heat preservation temperature and time of this embodiment can allow the polymeric metal halide salt to undergo complete hydrolysis and allow the generated HCl gas to undergo complete reaction to better remove the impurity phase on the surface of the oxide solid electrolyte.

[0073] In one embodiment, the preset depth is 3 nm to 7 nm; in this embodiment, through the etching process, the preset depth is etched on the surface of the electrolyte, thereby removing the impurity phase formed on the surface of the electrolyte due to ball milling and tablet pressing, enabling the tantalum-containing vapor to form a good interfacial phase with the halide electrolyte and making the interfacial phase more compact.

[0074] In one embodiment, the tantalum-containing vapor includes tantalum pentaiodide vapor or tantalum pentafluoride vapor; the sintering parameters are: the sintering temperature is 400℃ to 1200℃, and the sintering time is 2 h to 24 h; the introduction of the tantalum-containing vapor can prevent the reaction between the halide electrolyte coating layer and the lithium metal negative electrode, improving the stability of the lithium metal negative electrode.

[0075] The technical solutions of the present application will be described below through specific examples and comparative examples.

[0076] Example 1

[0077] A preparation method of a solid electrolyte, comprising:

[0078] Step 1, mix lithium chloride LiCl, AlCl3 (metal halide salt), and AlCl3·5H2O (polymeric metal halide salt) in a molar ratio of 6:8:1. Add the obtained halogenated mixture to a ball milling tank for gentle mixing ball milling. The material of the ball milling tank is agate, the ball-to-material ratio of ball milling is 20:1, the ball milling time is 360 min, and the ball milling rate is 50 r / min.

[0079] Step 2, during the ball milling process, add the oxide solid electrolyte in multiple times at 20-min intervals until the mass ratio of the oxide solid electrolyte to the halogenated mixture reaches 10:0.5. The mass of the oxide solid electrolyte added each time is 10% of the mass of the halogenated mixture. The D50 of the oxide solid electrolyte is 700 nm, and the oxide solid electrolyte is lithium lanthanum zirconium oxide (LLZO) electrolyte.

[0080] Step 3, during the continued ball milling process, allow the oxide solid electrolyte and the halogenated mixture to be fully mixed. Pause the ball milling every 20-min interval. Place the ball milling tank in a vacuum oven under an inert gas atmosphere for heat preservation at 260 °C to obtain electrolyte powder, and the heat preservation time is 30 min.

[0081] Step 4, press the electrolyte powder into a sheet in a tablet pressing mold to obtain an electrolyte sheet.

[0082] Step 5, place the electrolyte sheet in an etching machine and perform etching on the surface of the electrolyte sheet to a depth of 7 nm.

[0083] Step 6, place the etched electrolyte sheet in a crucible with a water-absorbing molecular sieve. The particles of the water-absorbing molecular sieve cover the electrolyte sheet. Place the crucible in a tantalum pentaiodide vapor atmosphere in a tube furnace for sintering to obtain a solid electrolyte with an amorphous non-crystalline phase halide electrolyte coating the oxide solid electrolyte. The sintering temperature is 700 °C, the sintering time is 10 h, and the molecular formula of the solid electrolyte is TaI5-LiAl 1.5 OCl 3.5 @LLZO.

[0084] Figure 2 It is the particle element distribution map after ball milling of the halogenated mixture and the oxide solid electrolyte, which are the raw materials of the amorphous non-crystalline phase halide electrolyte in Example 1; most of the aluminum element covers the surface of the oxide solid electrolyte, indicating that the amorphous non-crystalline phase halide electrolyte coats the oxide solid electrolyte.

[0085] Figure 3 For the amorphous non-crystalline phase halide electrolyte LiAl 1.5 OCl3.5 (abbreviated as LAOC) and the oxide solid electrolyte LLZO to synthesize the comparison diagram of the HCl concentration generated by the co-reaction and the HCl concentration generated by the reaction of LAOC alone; as Figure 3 shown, since the HCl concentration synthesized by the co-reaction of LAOC and LLZO is lower than the HCl concentration synthesized by the reaction of LAOC alone, it shows that the HCl generated by the co-reaction of LAOC and LLZO can remove the oxide impurities on the surface of LLZO particles.

[0086] Figure 4 The comparison diagram of the electrolyte impedance of the co-ball milling synthesis reaction of LAOC and LLZO in Example 1 and the electrolyte impedance of the initial LLZO particles, as Figure 4 shown, the electrolyte impedance of the co-synthesis reaction of LAOC and LLZO in Example 1 is lower than the electrolyte impedance of LLZO, indicating that after the chloride electrolyte removes the oxide impurities on the surface of LLZO particles and LAOC coats LLZO, the elastic modulus of the oxide electrolyte is reduced, thereby improving the ionic conductivity of the solid electrolyte.

[0087] Example 2: The difference from Example 1 is that the raw materials of the amorphous halide electrolyte are increased and some process parameters are changed;

[0088] A preparation method of a solid electrolyte, comprising:

[0089] Step 1, mix lithium chloride LiCl, AlCl3 (metal halide salt), RhCl3·5H2O (polymeric metal halide salt), and VCl3·5H2O (polymeric metal halide salt) in a molar ratio of 9:14:0.5:0.5, and add the obtained halogenated mixture to a ball milling tank for gentle mixing and ball milling. The material of the ball milling tank is agate, the ball-to-material ratio of the ball milling is 40:1, the ball milling time is 540 min, and the ball milling rate is 300 r / min.

[0090] Step 2, during the ball milling process, add the oxide solid electrolyte in multiple times at 30 min intervals until the mass ratio of the oxide solid electrolyte to the halogenated mixture reaches 10:2. The mass of each added oxide solid electrolyte is 10% of the mass of the halogenated mixture. The D50 of the oxide solid electrolyte is 1500 nm, and the oxide solid electrolyte is a lithium lanthanum titanium oxide (LLTO) electrolyte.

[0091] Step 3, during the continuous ball milling process, allow the oxide solid electrolyte and the halogenated mixture to be fully mixed. Pause the ball milling every 20 min interval, and place the ball milling tank in a vacuum oven under an inert gas atmosphere for heat preservation at 260 °C to obtain electrolyte powder, and the heat preservation time is 30 min.

[0092] Step 4: Press the electrolyte powder into a sheet in a tablet press mold to obtain an electrolyte sheet.

[0093] Step 5: Place the electrolyte sheet in an etching machine and perform etching to a depth of 3 nm on the surface of the electrolyte sheet.

[0094] Step 6: Place the etched electrolyte sheet in a crucible with a water-absorbing molecular sieve. The particles of the water-absorbing molecular sieve cover the electrolyte sheet. Place the crucible in a tantalum pentafluoride vapor atmosphere in a tube furnace for sintering to obtain a solid electrolyte with an amorphous non-crystalline phase halide electrolyte coating an oxide solid electrolyte. The molecular formula of the solid electrolyte is TaF5-Li 1.5 Al 1.25 Rh 0.625 V 0.625 OCl7@LLTO, the sintering temperature is 700 °C, and the sintering time is 10 h.

[0095] Example 3: The difference from Example 1 is that the raw materials of the amorphous non-crystalline phase halide electrolyte are increased, and some process parameters are changed;

[0096] A method for preparing a solid electrolyte, comprising:

[0097] Step 1: Mix lithium chloride LiCl, CaCl3 (halide metal salt), and AlCl3·5H2O (polymeric halide metal salt) in a molar ratio of 6:11:1. Add the obtained halide mixture to a ball mill jar for gentle mixing and ball milling. The material of the ball mill jar is agate, the ball-to-material ratio of ball milling is 35:1, the ball milling time is 280 min, and the ball milling rate is 250 r / min.

[0098] Step 2: During the ball milling process, add the oxide solid electrolyte in multiple portions at 60-min intervals until the mass ratio of the oxide solid electrolyte to the halide mixture reaches 10:0.15. The mass of the oxide solid electrolyte added each time is 10% of the mass of the halide mixture. The oxide solid electrolyte is a lithium lanthanum titanium oxide (LLTO) electrolyte and a lithium lanthanum zirconium oxide (LLZO) electrolyte. The D50 of the oxide solid electrolyte is 1000 nm, and the mass ratio of the lithium lanthanum titanium oxide (LLTO) electrolyte to the lithium lanthanum zirconium oxide (LLZO) electrolyte is 0.45:0.55.

[0099] Step 3: During the continued ball milling process, allow the oxide solid electrolyte and the halide mixture to be fully mixed. Pause the ball milling every 20-min interval, and place the ball mill jar in a vacuum oven under an inert gas atmosphere for heat preservation at 260 °C to obtain electrolyte powder. The heat preservation time is 30 min.

[0100] Step 4: Press the electrolyte powder into a sheet in a tablet press mold to obtain an electrolyte sheet.

[0101] Step 5: Place the electrolyte sheet into an etching machine and perform etching on the surface of the electrolyte sheet to a depth of 5 nm.

[0102] Step 6: Place the etched electrolyte sheet into a crucible with water-absorbing molecular sieves. The particles of the water-absorbing molecular sieves cover the electrolyte sheet. Place the crucible in a tantalum vapor atmosphere in a tube furnace for sintering to obtain a solid electrolyte with an amorphous non-crystalline phase halide electrolyte coating an oxide solid electrolyte. The molecular formula of the solid electrolyte is TaI5 / TaF5-LiCa 1.83 Al 0.17 OCl5@LLTO-LLZO. The sintering temperature is 700 °C, the sintering time is 10 h, the tantalum vapor is tantalum pentaiodide vapor and tantalum pentafluoride vapor, and the mass ratio of tantalum pentaiodide to tantalum pentafluoride is 5:95.

[0103] Comparative Example 1: The difference from Example 1 is that the raw material of the amorphous non-crystalline phase halide electrolyte does not include AlCl3 (metal halide salt).

[0104] Comparative Example 2: The difference from Example 1 is that the raw material of the amorphous non-crystalline phase halide electrolyte does not include AlCl3·5H2O (polymeric metal halide salt).

[0105] Comparative Example 3: The difference from Example 1 is that the molar ratio of lithium chloride LiCl, AlCl3 (metal halide salt), and AlCl3·5H2O (polymeric metal halide salt) is 11:21:1.

[0106] Comparative Example 4: The difference from Example 2 is that the mass ratio of the oxide solid electrolyte to the halogenated mixture is 1:1.

[0107] Comparative Example 5: The difference from Example 2 is that the oxide solid electrolyte is lithium aluminum titanium phosphate.

[0108] Comparative Example 6: The difference from Example 2 is that the D50 of the oxide solid electrolyte is 300 nm.

[0109] Comparative Example 7: The difference from Example 3 is that it does not include the tablet pressing in Step 4 and the etching in Step 5, and the electrolyte powder is sintered according to Step 6.

[0110] Comparative Example 8: The difference from Example 3 is that in Step 6, an argon atmosphere of inert gas is used instead of a tantalum vapor atmosphere.

[0111] Comparative Example 9: The difference from Example 3 is that the sintering temperature in Step 6 is 200 °C.

[0112] Data testing:

[0113] The electrolyte sheets obtained in Examples 1 to 3 and Comparative Examples 1 to 9 were assembled into all-solid-state batteries. NCM811 was used as the active material for the positive electrode, polyvinylidene fluoride (PVDF) as the binder, and super P as the conductive agent. Lithium metal foil with a thickness of 20 μm was used for the negative electrode. They were assembled in a mold battery with an assembly pressure of 5 Mpa. Charge-discharge cycle tests were carried out at 45 °C with a rate of 0.33 C for charging and 0.33 C for discharging. Coulombic efficiency = (discharge capacity / charge capacity) × 100%; The Coulombic efficiency and capacity retention rate of the charge-discharge cycles of each example and each comparative example were obtained, as shown in Table 1.

[0114]

[0115] As shown in Table 1, the Coulombic efficiency and capacity retention rate of the all-solid-state batteries corresponding to the solid electrolytes prepared in Examples 1 to 3 were significantly higher than those of each comparative example.

[0116] Figure 5 Schematic diagrams of the impedance of the solid electrolytes prepared by using tantalum pentaiodide vapor in Example 1 and using argon gas, an inert gas, without using tantalum pentaiodide vapor in Comparative Example 8, respectively.

[0117] Figure 6 Schematic diagrams of the cycles of Li / SE / Li symmetric batteries assembled with the solid electrolytes prepared in Example 1, Comparative Example 8, and Comparative Example 9. The voltage stability of the electrolyte sheet of Example 1 towards lithium metal was much higher than that of the electrolyte sheets of Comparative Examples 8 and 9 towards lithium metal.

[0118] Figure 7 Schematic diagram for comparing the capacity retention rate of all-solid-state batteries assembled with the solid electrolyte sheets prepared in Example 2 and Comparative Example 6 respectively; It shows that the D50 particles of the solid electrolyte need to be maintained within a certain range, and exceeding this range will cause a decline in the electrochemical performance of the all-solid-state battery.

[0119] It should be understood that the magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0120] In the above embodiments, the descriptions of each embodiment have their own focuses. For parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0121] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A solid electrolyte, characterized in that The solid electrolyte comprises an amorphous amorphous halide electrolyte, an oxide solid electrolyte and a tantalum-containing interface layer, wherein the amorphous amorphous halide electrolyte covers the oxide solid electrolyte, and the powder of the amorphous amorphous halide electrolyte covering the oxide solid electrolyte is pressed into a shape, and the tantalum-containing interface layer is coated on the surface of the pressed electrolyte; The molecular formula of the solid electrolyte is TaM5-Li a X b Y c OCl@LLNO; Among them, Li a X b Y c OCl is the amorphous non-crystalline halide electrolyte, LLNO is the oxide solid electrolyte, TaM5 is the tantalum-containing interface layer, M is iodine or fluorine, X is a first metal element, the first metal element is derived from a raw material halogenated metal salt, Y is a second metal element, the second metal element is derived from a raw material polymerized halogenated metal salt, N is zirconium and / or titanium, 1≤ a≤2, 0≤b≤5, 0≤c≤5, and at least one of b and c is greater than 0; The raw materials for preparing the solid electrolyte include lithium chloride, a metal halide salt and a polymerized metal halide salt, and the preset molar ratio of lithium chloride, the metal halide salt and the polymerized metal halide salt is (1-10) : (1-20) : 1; The D50 of oxide solid electrolytes is 700 nm~1500 nm; The polymerized metal halide salt includes one or more of AlCl3·nH2O, CaCl2·nH2O, CrCl2·nH2O, CuCl2·nH2O, CoCl2·nH2O, SnCl2·nH2O, RhCl2·nH2O, VCl2·nH2O, FeCl2·nH2O, wherein 1≤n≤6; The first metal element includes one or more of aluminum, calcium, chromium, gallium, zinc, magnesium, and tungsten.

2. The solid electrolyte according to claim 1, characterized in that The second metal element includes one or more of aluminum, calcium, chromium, copper, cobalt, tin, rhodium, vanadium, and iron; If the first metal element is the same as the second metal element, the value of b or c is 0.

3. The solid electrolyte according to claim 1, characterized in that The oxide solid electrolyte includes a combination of one or more of lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, and lithium lanthanum zirconium titanium oxide; The halogenated metal salt includes a combination of one or more of AlCl3, CaCl2, CrCl5, GaCl3, ZnCl2, MgCl2, and WCl5.

4. A method for preparing a solid electrolyte according to any one of claims 1 to 3, characterized in that: include: Mixing lithium chloride, a metal halide salt, and a polymerized metal halide salt according to a preset molar ratio, and adding the obtained halogenated mixture into a ball mill for ball milling; During the ball milling process, adding the oxide solid electrolyte multiple times at a first preset interval until the mass ratio of the oxide solid electrolyte to the halogenated mixture reaches a preset mass ratio, and the mass of the oxide solid electrolyte added each time is 5% to 15% of the mass of the halogenated mixture; During the ball milling process, the ball milling is stopped every second preset interval, and the ball mill is kept warm at a preset temperature under an inert gas atmosphere to obtain an electrolyte powder; Pressing the electrolyte powder into a shape to obtain an electrolyte; Etching the electrolyte to a preset depth; The etched electrolyte and the water-absorbing molecular sieve are sintered in a tantalum-containing steam atmosphere in a tube furnace to obtain a solid electrolyte.

5. The method for preparing a solid electrolyte according to claim 4, characterized in that: The ball-to-material ratio of the ball mill is (10~40) : 1, the ball milling time is 20 min~2400 min, and the ball milling speed is 1 r / min~1000 r / min.

6. The method for preparing a solid electrolyte according to claim 4, characterized in that: The first preset interval time is 10 min~30 min; The preset mass ratio of the oxide solid electrolyte to the halogenated mixture is 10:(0.1-5).

7. The method for preparing a solid electrolyte according to claim 4, characterized in that: The second preset interval time is 5 min to 10 min; The preset temperature is 100 ~300 The insulation time of the inert gas insulation is 10 min~60 min.

8. The method for preparing a solid electrolyte according to claim 4, characterized in that: The preset depth is 3nm~7nm.

9. The method for preparing a solid electrolyte according to claim 4, characterized in that: The tantalum-containing vapor includes tantalum pentaiodide vapor or tantalum pentafluoride vapor; The sintering parameters are: sintering temperature is 400 ~1200 , the sintering time is 2 h~24 h.

10. A solid-state lithium battery, characterized in that: The invention comprises the solid electrolyte as claimed in any one of claims 1 to 3, or the solid electrolyte obtained by the preparation method of the solid electrolyte as claimed in any one of claims 4 to 9.

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