Lithium-lanthanum-zirconium-oxygen-based solid electrolyte, composite solid electrolyte containing same, electrochemical device and electric device

Abstract

The invention discloses a lithium-lanthanum-zirconium-oxygen-based solid electrolyte, a composite solid electrolyte containing the lithium-lanthanum-zirconium-oxygen-based solid electrolyte, an electrochemical device and an electric device, and belongs to the technical field of electrochemical energy storage. According to the lithium lanthanum zirconium oxygen-based solid electrolyte provided by the invention, the coating layer is introduced to at least part of the surface of the oxide layer, and the coating layer comprises calcium fluoride, so that in an electrochemical device obtained through subsequent preparation, under the driving of an electric field, the calcium fluoride in the coating layer can react with lithium carbonate in the oxide layer to generate lithium fluoride and calcium carbonate; therefore, while the structural stability of the lithium lanthanum zirconium oxygen-based solid electrolyte is improved, the generated lithium fluoride can also effectively help to improve the ionic conductivity and reduce the interface impedance; in addition, generated calcium carbonate can also help to stabilize the structure, and damage of lithium dendrites is avoided; therefore, the cycle performance of the prepared electrochemical device is effectively improved.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, and in particular to lithium lanthanum zirconium oxy-based solid electrolytes, composite solid electrolytes containing the same, and electrochemical devices and electrical devices. Background Technology

[0002] Solid-state batteries, which use non-flammable solid electrolytes instead of organic electrolytes, hold promise for breaking through the energy density bottleneck of lithium-ion batteries and fundamentally solving safety issues, making them an important direction for next-generation energy storage technology. Current development focuses on improving the ionic conductivity of solid electrolytes and optimizing the solid-solid interface compatibility and stability between electrodes and electrolytes.

[0003] Garnet-type Li7La3Zr2O 12 LLZO solid-state electrolytes are considered key materials for next-generation high-energy-density lithium batteries due to their high ionic conductivity, good stability to lithium metal, and wide electrochemical window. However, LLZO is highly sensitive to H2O and CO2 in the air, and an inert Li2CO3 layer easily forms on its surface, resulting in extremely high interfacial impedance. Composites of LLZO with polymers as inorganic fillers are an effective strategy for preparing flexible solid-state electrolytes; however, the Li2CO3 layer on the LLZO surface severely hinders ion transport between the filler and the polymer matrix, becoming a "dead zone" for ion migration in the composite electrolyte and significantly reducing overall ionic conductivity. This leads to increased battery polarization, capacity decay, and may induce lithium dendrite growth, severely hindering its practical application. Summary of the Invention

[0004] The purpose of this application is to solve the technical problem that the lithium carbonate oxide layer formed by the lithium lanthanum zirconium oxy solid electrolyte in the prior art generates a large interfacial impedance, resulting in poor cycle performance of subsequent electrochemical devices (such as solid-state batteries) and a large number of lithium dendrites. The application proposes a lithium lanthanum zirconium oxy solid electrolyte, a composite solid electrolyte containing the electrolyte, an electrochemical device, and an electrical device, which have high ionic conductivity, low interfacial impedance, long lithium dendrite suppression lifetime, and excellent cycle performance of the prepared electrochemical device.

[0005] To achieve the above objectives, a first aspect of this application provides a lithium lanthanum zirconium oxy-oxide solid electrolyte, the lithium lanthanum zirconium oxy-oxide solid electrolyte comprising an LLZO core, an oxide layer disposed on at least a portion of the surface of the core, and a coating layer disposed on at least a portion of the surface of the oxide layer; The oxide layer includes Li2CO3; The coating layer includes CaF2.

[0006] As an embodiment of this application, the lithium lanthanum zirconium oxy-oxide solid electrolyte satisfies 10 ≤ D / T ≤ 80; Where D nm is the diameter of the kernel; T nm is the thickness of the coating layer.

[0007] As an embodiment of this application, the diameter D nm of the kernel is 100-5000.

[0008] As an embodiment of this application, the thickness T nm of the coating layer is 10-500.

[0009] As an embodiment of this application, the thickness of the oxide layer is 2-20 nm.

[0010] As an embodiment of this application, the mass percentage of CaF2 is 5-90% based on the total mass of the lithium lanthanum zirconium oxide solid electrolyte.

[0011] As an embodiment of this application, the average particle size of the CaF2 is 5-200 nm.

[0012] A second aspect of this application provides a composite solid electrolyte, including the lithium lanthanum zirconium oxy-oxide solid electrolyte described in this application.

[0013] As an embodiment of this application, the mass percentage of the lithium lanthanum zirconium oxy-based solid electrolyte is 30-70% based on the total mass of the composite solid electrolyte.

[0014] As an embodiment of this application, the composite solid electrolyte further includes a lithium salt and a polymer matrix.

[0015] A third aspect of this application provides an electrochemical device comprising a positive electrode, a negative electrode, and a composite solid electrolyte membrane, wherein the composite solid electrolyte membrane comprises the composite solid electrolyte described in this application.

[0016] As an embodiment of this application, the electrochemical device satisfies: 2≤Y≤400; Where Y = (H × T) / R; H μm is the thickness of the composite solid electrolyte membrane; T nm is the thickness of the coating layer; R nm is the average particle size of CaF2.

[0017] As an embodiment of this application, the thickness of the composite solid electrolyte membrane is 1-30 μm.

[0018] In a fourth aspect, this application provides an electronic device, which includes the electrochemical device described in this application.

[0019] Compared with the prior art, the beneficial effects of this application are: The lithium lanthanum zirconium oxide solid electrolyte provided in this application introduces a coating layer on at least a portion of the surface of the oxide layer, and the coating layer includes calcium fluoride. In the subsequently prepared electrochemical device, under the drive of an electric field, the calcium fluoride in the coating layer can react with the lithium carbonate in the oxide layer to generate lithium fluoride and calcium carbonate. This improves the structural stability of the lithium lanthanum zirconium oxide solid electrolyte, while the generated lithium fluoride can effectively help improve ionic conductivity and reduce interfacial impedance. In addition, the generated calcium carbonate can also help stabilize the structure and avoid damage from lithium dendrites, thereby effectively improving the cycle performance of the prepared electrochemical device. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] The term "polymer" refers to a polymeric compound prepared by polymerizing the same or different types of monomers. The general term "polymer" includes the terms "homopolymer," "copolymer," "trimer," and "interpolymer."

[0022] The term "binder" refers to a substance used to bind inorganic fillers to or to porous substrate materials.

[0023] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0024] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0025] As used herein, the terms “approximately,” “generally,” “substantially,” and “about” are used to describe and indicate small variations. When used in conjunction with an event or situation, the terms may refer to examples in which the event or situation occurred precisely and examples in which the event or situation occurred very approximately. For example, when used in conjunction with numerical values, the terms may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. For example, if the difference between two values ​​is less than or equal to ±10% of the average of the values ​​(e.g., less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%), then the two values ​​can be considered "substantially" the same.

[0026] Furthermore, for ease of description, "first," "second," "third," etc., can be used in this document to distinguish one or a series of different components. "First," "second," "third," etc., are not intended to describe the corresponding components.

[0027] Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format in this document. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only the numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0028] In the detailed description and claims, a list of items connected by the terms "one of," "among," "a kind of," or other similar terms may mean any of the listed items. For example, if items A and B are listed, then the phrase "one of A and B" means only A or only B. In another example, if items A, B, and C are listed, then the phrase "one of A, B, and C" means only A; only B; or only C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0029] In the detailed description and claims, the list of items connected by the term "at least one of" can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.

[0030] In the following description, all figures disclosed in this application are approximate values, regardless of whether the terms "about" or "approximately" are used in conjunction. They may vary by 1%, 2%, 5%, or sometimes 10% to 20%. Whenever a range of values ​​with a lower limit (RL) and an upper limit (RU) is disclosed, any values ​​falling within that range are specifically disclosed. Specifically, the following values ​​within this range are specifically disclosed: R = RL + k × (RU - RL), where k is a variable with a 1% increment from 1% to 100%, i.e., k is 1%, 2%, 3%, 4%, 5%, ..., 50%, 51%, 52%, ..., 95%, 96%, 97%, 98%, 99%, or 100%. Furthermore, any range of values ​​defined by the two R values ​​as defined above are also specifically disclosed.

[0031] Throughout this specification, references to "implementation," "partial implementation," "one implementation," "another implementation," "specific method," or "partial method" mean that at least one implementation or embodiment in this application includes the specific features, structures, materials, or characteristics described in that implementation or embodiment.

[0032] In this application, numerical ranges are involved. Unless otherwise specified, the numerical ranges mentioned above are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form a range not explicitly stated.

[0033] Unless otherwise specified, all reagents or instruments used in this application are commercially available products.

[0034] In one embodiment of this application, a first aspect of this application provides a lithium lanthanum zirconium oxy-oxide solid electrolyte, the lithium lanthanum zirconium oxy-oxide solid electrolyte comprising an LLZO core, an oxide layer disposed on at least a portion of the surface of the core, and a coating layer disposed on at least a portion of the surface of the oxide layer; The oxide layer includes Li2CO3; The coating layer includes CaF2.

[0035] The lithium lanthanum zirconium oxide solid electrolyte provided in this application introduces a coating layer on at least a portion of the surface of the oxide layer, and the coating layer includes calcium fluoride. In the subsequently prepared electrochemical device, under the drive of an electric field, the calcium fluoride in the coating layer can react with the lithium carbonate in the oxide layer to generate lithium fluoride and calcium carbonate. This improves the structural stability of the lithium lanthanum zirconium oxide solid electrolyte, while the generated lithium fluoride can effectively help improve ionic conductivity and reduce interfacial impedance. In addition, the generated calcium carbonate can also help stabilize the structure and avoid damage from lithium dendrites, thereby effectively improving the cycle performance of the prepared electrochemical device.

[0036] Specifically, calcium fluoride in the coating layer reacts with lithium carbonate in the oxide layer under an electric field, specifically Li₂CO₃ + CaF₂ → 2LiF + CaCO₃. This allows for the introduction of lithium fluoride with good ionic conductivity while consuming high-resistivity lithium carbonate, thereby improving the overall ion conduction level. Furthermore, the formed calcium carbonate has a stable structure, stabilizing the lithium lanthanum zirconium oxide solid electrolyte, thus further reducing interfacial impedance and improving overall ionic conductivity. Additionally, the formed calcium carbonate stabilizes the formed lithium fluoride / calcium carbonate interface layer, enhancing its stability and improving the structural stability of the subsequently obtained composite solid electrolyte membrane, preventing lithium dendrite damage in the later stages of cycling. This effectively improves the cycling performance of the electrochemical device.

[0037] It should be noted that the substances in the oxide layer and the coating layer are obtained by X-ray diffraction. For example, the presence of a diffraction peak at approximately 21.32° in the XRD diffraction pattern indicates that the oxide layer contains Li2CO3, and the presence of diffraction peaks at approximately 28.27°, 47.00°, and 55.76° in the XRD diffraction pattern indicates that the coating layer contains CaF2.

[0038] In one embodiment, the lithium lanthanum zirconium oxy-oxide solid electrolyte satisfies 1 ≤ D / T ≤ 200; Where D nm is the diameter of the kernel; T nm is the thickness of the coating layer.

[0039] It should be noted that the test method for the diameter of the core and the thickness of the coating layer is as follows: by using a high-resolution transmission electron microscope (TEM) and an energy dispersive spectroscopy (EDS) to perform a line scan along the direction perpendicular to the particle surface, the intensity distribution curves of La, Zr, O, Ca and F elements are plotted; the length of the plateau interval of the curve corresponds to the size of the LLZO core, and the width of the Ca / F signal rising from the background value to the peak value and then falling back to the background value is the coating layer thickness.

[0040] For example, D / T can be any point value between 1 and 200 or a range value between any two points, such as 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, etc.

[0041] In one embodiment, the lithium lanthanum zirconium oxy-oxide solid electrolyte satisfies 10 ≤ D / T ≤ 30.

[0042] For example, D / T can be any point value between 10 and 30 or a range value between any two points, such as 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, etc.

[0043] This study found that the D / T ratio affects several factors. First, it influences the efficiency of the LLZO layer, thus affecting ionic conductivity and interfacial impedance. It also affects the degree to which calcium fluoride consumes lithium carbonate from the oxide layer under an electric field, further impacting ionic conductivity and interfacial impedance. Second, the ratio affects the amount of calcium carbonate produced by the reaction of calcium fluoride and lithium carbonate under an electric field, thus influencing structural stability. Finally, it affects the coating effect on the LLZO, thereby impacting the extent of side reactions during cycling and the stability of the LLZO structure. When the D / T ratio is further selected within the aforementioned range, especially within a more optimized range, the resulting solid-state battery exhibits superior cycle performance.

[0044] In one embodiment, the diameter D nm of the kernel is 100-5000.

[0045] For example, the diameter D nm of the kernel can be any point value between 100 and 5000 or a range value between any two points, such as 100, 200, 400, 600, 800, 1000, 1200, 1500, 1800, 2000, 2200, 2500, 2800, 3000, 3200, 3500, 3800, 4000, 4200, 4500, 4800, 5000, etc.

[0046] In one embodiment, the diameter D nm of the kernel is 2000-3000. For example, it can be 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, 3000, etc.

[0047] This study found that the diameter of the core affects its packing density during the subsequent formation of the composite solid electrolyte membrane, thereby influencing the interfacial impedance and resistance to lithium dendrite penetration. It also affects the core's specific surface area, thus impacting its ability to undergo side reactions and consequently its structural stability. Further selection of the core diameter within the aforementioned range, particularly within a more optimized range, results in a solid-state battery with superior overall performance.

[0048] In one embodiment, the thickness T nm of the coating layer is 10-500.

[0049] For example, the thickness T nm of the coating layer can be any point value between 10 and 500 or a range value between any two points, such as 10, 20, 50, 80, 100, 120, 150, 180, 200, 220, 250, 280, 300, 320, 350, 380, 400, 420, 450, 480, 500, etc.

[0050] In one embodiment, the thickness T nm of the coating layer is 100-200. For example, it can be 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, etc.

[0051] This study found that the thickness of the coating layer affects the overall particle size of the lithium lanthanum zirconium oxide solid electrolyte, thus influencing the density of the formed composite solid electrolyte film and consequently its resistance to lithium dendrite penetration and ionic conductivity. It also affects the ability to consume lithium carbonate in the oxide layer on the LLZO core surface and the isolation capability of the LLZO core. Furthermore, during the subsequent fabrication of solid-state batteries, it affects the reactivity with lithium carbonate in the SEI layer on the negative electrode surface, thereby affecting interfacial impedance and ion transport efficiency, as well as the density of the SEI, thus impacting its ability to resist lithium dendrite penetration. When the coating layer thickness is further selected within the above-mentioned range, especially within a more preferred range, the cycle performance of the subsequently fabricated electrochemical device is superior.

[0052] In one embodiment, the thickness of the oxide layer is 2-8 nm.

[0053] It should be noted that the method for testing the thickness of the oxide layer is as follows: the LLZO core with clear lattice fringes and the interface layer of the oxide layer can be clearly observed by high-resolution TEM, and the interface thickness of the oxide layer can be directly measured.

[0054] For example, the thickness of the oxide layer can be any point value between 2 and 8 nm or a range between any two points, such as 2 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, etc.

[0055] This study found that the thickness of the oxide layer affects the ionic conductivity of the lithium lanthanum zirconium oxide solid electrolyte, as well as the amount of lithium fluoride and calcium carbonate subsequently formed, thereby further affecting the ionic conductivity and the overall structural stability of the material. When the oxide layer thickness is further selected within the above-mentioned range, the overall performance of the resulting electrochemical device is superior.

[0056] In one embodiment, the mass percentage of CaF2 is 5-90% based on the total mass of the lithium lanthanum zirconium oxy-oxide solid electrolyte.

[0057] It should be noted that, based on the total mass of the lithium lanthanum zirconium oxy-coated solid electrolyte, the method for testing the mass percentage of CaF2 is as follows: by inductively coupled plasma (ICP) analysis, the lithium lanthanum zirconium oxy-coated solid electrolyte is first acid-digested, and then the concentrations of Ca and F elements in the sample are tested, and finally the mass percentage of CaF2 is calculated.

[0058] For example, based on the total mass of the lithium lanthanum zirconium oxy-oxide solid electrolyte, the mass percentage of CaF2 can be any point value between 5% and 90% or a range between any two points, such as 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, etc.

[0059] In one embodiment, the mass percentage of CaF2 is 40-60% based on the total mass of the lithium lanthanum zirconium oxy-oxide solid electrolyte. For example, it can be 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, etc.

[0060] This study found that the mass percentage of calcium fluoride in the lithium lanthanum zirconium oxide solid electrolyte affects the consumption of lithium carbonate in the oxide layer on the LLZO core surface and its isolation ability from the LLZO core. Furthermore, during the subsequent fabrication of solid-state batteries, it also affects the reactivity with lithium carbonate in the SEI layer on the negative electrode surface, thereby influencing interfacial impedance and ion transport efficiency, as well as the density of the SEI, thus affecting its ability to prevent lithium dendrite penetration. When the mass percentage of calcium fluoride in the lithium lanthanum zirconium oxide solid electrolyte is further selected within the above-mentioned range, and especially within a further preferred range, the cycle performance of the subsequently prepared electrochemical device is superior.

[0061] In one embodiment, the average particle size of the CaF2 is 5-200 nm.

[0062] It should be noted that the average particle size of CaF2 is measured by using TEM to clearly observe the LLZO core and the CaF2 coating layer. The particle size of three particles at each of the four positions of the outermost layer is directly measured, and the average value is taken as the average particle size of CaF2.

[0063] For example, the average particle size of the CaF2 can be any point value between 5 and 200 nm or a range between any two points, such as 5 nm, 15 nm, 25 nm, 35 nm, 45 nm, 55 nm, 65 nm, 75 nm, 85 nm, 95 nm, 105 nm, 115 nm, 125 nm, 135 nm, 145 nm, 155 nm, 165 nm, 175 nm, 185 nm, 195 nm, 200 nm, etc.

[0064] In one embodiment, the average particle size of the CaF2 is 50-100 nm. For example, it can be 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, etc.

[0065] This study found that the average particle size of calcium fluoride affects its ability to react with lithium carbonate in the oxide layer and the SEI film under an electric field, as well as the surface uniformity of the coating layer and its ability to protect the LLZO core. When the average particle size of calcium fluoride is further selected within the above-mentioned range, and especially within a more preferred range, the overall performance of the resulting electrochemical device is superior.

[0066] In one embodiment, the preparation method of the lithium lanthanum zirconium oxy-oxide solid electrolyte includes the following steps: (1) The lithium source, lanthanum source and zirconium source were mixed in stoichiometric ratio and then ball-milled. After ball milling, the mixture was calcined, ground and sieved to obtain LLZO cores. (2) The LLZO core and calcium fluoride were mixed in proportion and ball-milled to obtain lithium lanthanum zirconium oxide solid electrolyte.

[0067] In some embodiments, in step (1), the lithium source includes lithium carbonate; the lanthanum source includes lanthanum oxide; and the zirconium source includes zirconium oxide.

[0068] In some embodiments, in step (1), the dispersant used for ball milling includes ethanol; the ball milling time is 20-28 hours, and the ball milling speed is 150-450 rpm.

[0069] In some embodiments, in step (1), the calcination temperature is 850-950℃ and the calcination time is 8-12h.

[0070] In some embodiments, in step (2), the ball milling medium includes zirconium oxide; the ball milling time is 10-14 hours, and the ball milling speed is 300-500 rpm.

[0071] It should be noted that the diameter of the LLZO core can be controlled by adjusting the grinding time and the sieve mesh size in step (1).

[0072] It should be noted that the thickness of the oxide layer can be controlled by adjusting the grinding time in step (1) and whether it is exposed to air.

[0073] It should be noted that by adjusting the particle size of calcium fluoride in step (2), the average particle size of calcium fluoride in the coating layer can be changed.

[0074] It should be noted that by adjusting the amount of calcium fluoride and LLZO core added in step (2), the mass percentage of calcium fluoride in the lithium lanthanum zirconium oxide solid electrolyte and the thickness of the coating layer can be changed; at the same time, the thickness of the coating layer can also be changed by adjusting the speed and time of the ball mill.

[0075] A second aspect of this application provides a composite solid electrolyte, said composite solid electrolyte including the lithium lanthanum zirconium oxy-oxide solid electrolyte described in this application.

[0076] In one embodiment, the lithium lanthanum zirconium oxy-based solid electrolyte comprises 30-70% by mass of the total mass of the composite solid electrolyte.

[0077] It should be noted that, based on the total mass of the composite solid electrolyte, the test method for the mass percentage of the lithium lanthanum zirconium oxy solid electrolyte is as follows: First, weigh and record the total mass M of the composite solid electrolyte; second, dissolve the composite solid electrolyte in N-methylpyrrolidone (NMP) to remove the lithium salt and polymer matrix from the composite solid electrolyte; filter and dry to obtain the lithium lanthanum zirconium oxy solid electrolyte and weigh and record its mass as Ms; finally, the ratio of Ms / M is the mass percentage of the lithium lanthanum zirconium oxy solid electrolyte in the composite solid electrolyte.

[0078] For example, based on the total mass of the composite solid electrolyte, the mass percentage of the lithium lanthanum zirconium oxy-oxide solid electrolyte can be any point value between 30% and 70% or a range between any two points, such as 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc.

[0079] This study found that the mass percentage of lithium lanthanum zirconium oxy-based solid electrolyte in the composite solid electrolyte affects its performance, such as influencing ionic conductivity and interfacial impedance, as well as structural stability. When the mass percentage of lithium lanthanum zirconium oxy-based solid electrolyte in the composite solid electrolyte is further selected within the aforementioned range, the resulting electrochemical device exhibits superior overall performance.

[0080] In one embodiment, the composite solid electrolyte further includes a lithium salt and a polymer matrix.

[0081] This application does not have any special requirements for the selection of lithium salt. For example, the lithium salt may be LiTFSI, LiFSI, LiDFOB, LiClO4, LiBF4, LiPF6, etc.

[0082] This application does not have any special requirements for the polymer matrix. For example, the polymer matrix may be PVDF, PVDF-HFP, PEO, PMMA, PAN, PPC, PEC, PVC, PCL, etc.

[0083] In one embodiment, the method for preparing the composite solid electrolyte membrane includes the following steps: The polymer matrix was dissolved in NMP, and then lithium salt and lithium lanthanum zirconium oxy-based solid electrolyte were added and stirred. The mixture was then cast and dried to obtain a composite solid electrolyte membrane.

[0084] In some embodiments, the polymer matrix has a mass percentage of 5-15% in NMP.

[0085] In some embodiments, the stirring time is 10-14 hours.

[0086] In some embodiments, the drying is vacuum drying, with a drying temperature of 55-100°C and a drying time of 20-28 hours.

[0087] It should be noted that the mass percentage of lithium lanthanum zirconium oxy-based solid electrolyte in the composite solid electrolyte can be changed by adjusting the amount of lithium lanthanum zirconium oxy-based solid electrolyte added.

[0088] A third aspect of this application provides an electrochemical device comprising a positive electrode, a negative electrode, and a composite solid electrolyte membrane, wherein the composite solid electrolyte membrane comprises the composite solid electrolyte described in this application.

[0089] In one embodiment, the electrochemical device satisfies: 2≤Y≤400; Where Y = (H × T) / R; H μm is the thickness of the composite solid electrolyte membrane; T nm is the thickness of the coating layer; R nm is the average particle size of CaF2.

[0090] This study found that further limiting the electrochemical device to satisfy 2≤(H×T) / R≤400 enables the composite solid electrolyte membrane in the electrochemical device to not only meet certain mechanical strength requirements, but also ensure the integrity of the coating layer, excellent interface stability, and suitable ion transport pathway. Furthermore, the calcium fluoride in the coating layer can further undergo a cation exchange reaction with the lithium carbonate in the SEI film on the lithium metal anode surface, forming high-modulus lithium fluoride and a stable and tough SEI rich in calcium carbonate at the interface layer, thereby achieving dense lithium deposition and further improving the cycle performance of the electrochemical device.

[0091] In one embodiment, the thickness of the composite solid electrolyte membrane is 1-30 μm.

[0092] It should be noted that the test method for the thickness of the composite solid electrolyte membrane is as follows: measure the thickness of the composite solid electrolyte membrane at 5 different locations using a micrometer, and then take the average value as the thickness of the composite solid electrolyte membrane.

[0093] For example, the thickness of the composite solid electrolyte membrane can be any point value or a range between any two points between 1 and 30 μm, such as 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, etc.

[0094] This study found that the thickness of the composite solid electrolyte membrane affects its ion transport resistance, as well as its mechanical strength and safety as a physical barrier; when the thickness of the composite solid electrolyte membrane is further selected within the above range, the overall performance of the resulting electrochemical device is better.

[0095] In one embodiment, the positive electrode sheet includes a current collector and a positive active material layer disposed on at least one surface of the current collector, the positive active material layer including a positive active material, a positive conductive agent, and a positive binder.

[0096] This application does not have any special requirements for the selection of the positive electrode active material; conventionally available positive electrode active materials in the art can be used. For example, the positive electrode active material may be selected from LiCoO2, LiNiO2, or LiNi. x Mn y O2, Li 1+z Ni x Mn y Co 1-x- y O2, LiNi x Co y Al z The group consisting of O2, LiV2O5, LiMnO2, LiMn2O4, Li2MnO3, LiFeO2, LiFePO4, LiMnPO4, and combinations thereof, wherein each x is independently 0.2 to 0.9; each y is independently 0.1 to 0.45; and each z is independently 0 to 0.2. The positive electrode active material of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as positive electrode active materials.

[0097] Alternatively, the positive electrode active material can be selected from LiCoO2, LiNiO2, or LiNi. x Mn y O2, Li 1+z NixMnyCo 1-x-y O2, LiNi x Co y Al z The group consisting of O2, LiV2O5, LiMnO2, LiMn2O4, LiFeO2, LiFePO4 and combinations thereof, wherein each x is independently 0.4 to 0.6; each y is independently 0.2 to 0.4; and each z is independently 0 to 0.1.

[0098] Or the positive electrode active material is Li 1+x Ni a Mn b Co c Al (1-a-b-c)O2; where -0.2≤x≤0.2, 0≤a<1, 0≤b<1, 0≤c<1 and a+b+c≤1.

[0099] Or the positive electrode active material is Li 1+x Ni a Mn b Co c Al (1-a-b-c) O2, where 0.33≤a≤0.92, 0.33≤a≤0.9, 0.33≤a≤0.8, 0.5≤a≤0.92, 0.5≤a≤0.9, 0.5≤a≤0.8, 0.6≤a≤0.92 or 0.6≤a≤0.9; 0≤b≤0.5, 0≤b≤0.3, 0.1≤b≤0.5, 0.1≤b≤0.4, 0.1≤b≤0.3, 0.1≤b≤0.2 or 0.2≤b≤0.5; 0≤c≤0.5, 0≤c≤0.3, 0.1≤c≤0.5, 0.1≤c≤0.4, 0.1≤c≤0.3, 0.1≤c≤0.2 or 0.2≤c≤0.5.

[0100] In some embodiments, the positive electrode active material is doped with a dopant selected from the group consisting of Fe, Ni, Mn, Al, Mg, Zn, Ti, La, Ce, Sn, Zr, Ru, Si, Ge, and combinations thereof. In some embodiments, the dopant is not Fe, Ni, Mn, Mg, Zn, Ti, La, Ce, Ru, Si, or Ge. In some embodiments, the dopant is not Al, Sn, or Zr.

[0101] In some embodiments, the positive electrode active material may include LiNi. 0.33 Mn 0.33 Co 0.33 O2, LiNiO2, LiNi 0.4 Mn 0.4 Co 0.2 O2, LiNi 0.5 Mn 0.3 Co 0.2 O2, LiNi 0.6 Mn 0.2 Co 0.2 O2, LiNi 0.7 Mn 0.15 Co 0.15 O2, LiNi 0.8 Mn 0.1 Co 0.1 O2, LiNi 0.92 Mn 0.04 Co 0.04 O2, LiNi 0.8 Co 0.15 Al 0.05At least one of O2.

[0102] This application does not have specific requirements for the selection of the positive electrode binder; conventionally available positive electrode binders in the art can be used. Exemplarily, the positive electrode binder may be at least one of the following: polyvinylidene fluoride (PVDF), poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, polyacrylic acid, polyacrylonitrile, polyimide, polyurethane, polyvinyl butyral, polyvinylpyrrolidone (PVP), acrylic acid-acrylonitrile-acrylamide copolymer, and acrylic acid-acrylonitrile-acrylate copolymer. The positive electrode binder in this application is not limited to the above materials and also includes other materials that can be used as battery positive electrode binders.

[0103] This application does not have any special requirements for the selection of the positive electrode conductive agent; conventionally available positive electrode conductive agents in the art can be used. For example, the positive electrode conductive agent may be at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon nanotubes, carbon nanotubes, activated carbon, and mesoporous carbon. The positive electrode conductive agent in this application is not limited to the above materials and also includes other materials that can be used as positive electrode conductive agents in batteries.

[0104] In some embodiments, the negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector.

[0105] In some embodiments, the negative current collector is a metal foil or a composite current collector. In some embodiments, the metal foil is a copper foil. The composite current collector may include a metal foil substrate and a conductive layer disposed on at least one side of the metal foil substrate.

[0106] In some embodiments, the conductive layer may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fiber, carbon nanofiber, graphitized carbon sheet, carbon tube, carbon nanotube, activated carbon, and mesoporous carbon.

[0107] In some embodiments, the negative electrode active material may include natural graphite particles, synthetic graphite particles, hard carbon, soft carbon, mesophase carbon microspheres (MCMB), Sn, SnO2, SnO, Li4Ti5O 12 The negative electrode active material is selected from at least one of LTO, Si material, silicon-carbon (Si-C) composite material, silicon-nitrogen (Si-N) composite material, and silicon-oxygen (Si-O) composite material. The negative electrode active material of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as negative electrode active materials for batteries.

[0108] In some embodiments, the negative electrode binder may include at least one of polyacrylic acid, polymethacrylic acid, polyacrylate, polymethacrylate, polyacrylamide, styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylic acid-acrylonitrile-acrylamide copolymer, acrylic acid-acrylonitrile-acrylate copolymer, acrylonitrile-butadiene rubber, nitrile rubber, acrylonitrile-styrene-butadiene copolymer, acryloyl rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyvinyl alcohol, polyvinyl acetate, polyepoxychloropropane, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, carboxymethyl chitosan, polyester, polyamide, polyether, polyimide, polycarboxylic acid ester, polycarboxylic acid, polyurethane, alginate, fluorinated polymer, chlorinated polymer, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropylene. The negative electrode binder of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as battery negative electrode binders.

[0109] In some embodiments, the negative electrode conductive agent may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon nanotubes, carbon nanotubes, activated carbon, and mesoporous carbon. The negative electrode conductive agent of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as battery negative electrode conductive agents.

[0110] In a third aspect, this application provides an electronic device, which includes the electrochemical device described in this application.

[0111] The electronic device described in this application is not particularly limited and may be any electronic device known in the prior art.

[0112] The application of the electrochemical device of the present invention is not particularly limited, and it can be used in any electronic device known in the prior art. According to some embodiments of the present invention, the electronic devices include, but are not limited to, mobile phones, smartphones, laptops, tablets, wearable devices, smartwatches, smart bracelets, smart glasses, power banks, televisions, game consoles, game controllers, digital cameras, smart speakers, headphones, keyboards, mice, monitors, drones, audio equipment, home appliances, toys, power tools, automobiles, motorcycles, electric bicycles, bicycles, robots, robot dogs, industrial robots, android robots, etc.

[0113] Example 1 This application provides a lithium lanthanum zirconium oxy-based solid electrolyte, a composite solid electrolyte membrane, and a solid-state battery. The preparation method of the lithium lanthanum zirconium oxy-based solid electrolyte, the composite solid electrolyte membrane, and the solid-state battery includes the following steps: (1) Preparation of lithium lanthanum zirconium oxy-based solid electrolyte S1. Li2CO3, La2O3, and ZrO2 were mixed in a stoichiometric ratio of Li:La:Zr = 7:3:2. Ethanol was added as a dispersant, and the mixture was ball-milled for 24 hours (300 rpm). Then, the mixture was calcined at 900°C for 10 hours. After that, it was crushed and sieved to obtain LLZO particles with an average diameter of 2000 nm. The thickness of the oxide layer formed by the LLZO during the crushing and sieving process was 5 nm. S2. Mix LLZO particles and CaF2 powder (average particle size 50 nm) at a mass ratio of 60:40 (CaF2 accounts for 40% of the total mass of the composite filler), put them into a ball mill jar, use zirconia balls as the medium, and ball mill for 12 hours (400 rpm) to obtain a coating layer with a thickness of 100 nm. (2) Preparation of composite solid electrolyte membrane S3. Dissolve PVDF in NMP to form a 10 wt% solution, then add LiTFSI (50% of the mass of PVDF), and then add lithium lanthanum zirconium oxy-based solid electrolyte (50% of the total mass of PVDF, lithium salt, and lithium lanthanum zirconium oxy-based solid electrolyte). Stir for 12 h to form a uniform slurry. Cast the slurry onto a glass plate and then vacuum dry at 60 °C for 24 h to obtain a composite solid electrolyte membrane with a thickness of 20 μm. (3) Preparation of solid-state batteries First, a uniform slurry is prepared by dispersing LiCoO2, conductive agent Super P, and binder polyvinylidene fluoride in NMP solvent at a mass ratio of 97:1.5:1.5. This slurry is then coated onto an aluminum current collector. After vacuum drying to remove NMP and moisture, it is rolled and cut into small discs with a diameter of 14 mm, which serve as the positive electrode of the solid electrolyte. The negative electrode is a lithium-copper composite strip with a lithium metal layer thickness of 50 μm, cut into small discs with a diameter of 16 mm. The composite electrolyte membrane is dried and then cut into small discs with a diameter of 19 mm. Finally, the negative electrode, the composite solid electrolyte membrane, and the positive electrode are stacked sequentially to assemble a CR2032 coin cell, which is the solid-state battery.

[0114] Examples 2-4 This application provides a lithium lanthanum zirconium oxy-based solid electrolyte, a composite solid electrolyte membrane, and a solid battery. The difference between the preparation method of the lithium lanthanum zirconium oxy-based solid electrolyte, the composite solid electrolyte membrane, and the solid battery and that of Example 1 is that the crushing and sieving process in step S1 is adjusted to change the diameter of the LLZO core, so as to achieve the parameters in Table 1.

[0115] Examples 5-7 This application provides a lithium lanthanum zirconium oxy-based solid electrolyte, a composite solid electrolyte membrane, and a solid battery. The preparation method of the lithium lanthanum zirconium oxy-based solid electrolyte, the composite solid electrolyte membrane, and the solid battery differs from that of Example 1 in that the amount of calcium fluoride added in step S2 and the rotation speed and time of the ball mill are adjusted to change the coating thickness and the mass percentage of calcium fluoride in the lithium lanthanum zirconium oxy-based solid electrolyte, so as to achieve the parameters in Table 1.

[0116] Examples 8-9 This application provides a lithium lanthanum zirconium oxide solid electrolyte, a composite solid electrolyte membrane, and a solid battery. The preparation method of the lithium lanthanum zirconium oxide solid electrolyte, the composite solid electrolyte membrane, and the solid battery differs from that of Example 1 in that the pulverization time in step S1 is adjusted or the time of exposing the pulverized LLZO particles to air is adjusted to change the oxide layer thickness, so as to achieve the parameters in Table 1.

[0117] Examples 10-12 This application provides a lithium lanthanum zirconium oxy-based solid electrolyte, a composite solid electrolyte membrane, and a solid battery. The preparation method of the lithium lanthanum zirconium oxy-based solid electrolyte, the composite solid electrolyte membrane, and the solid battery differs from that of Example 1 in that the average particle size of calcium fluoride in step S2 is adjusted to change the average particle size of calcium fluoride in the lithium lanthanum zirconium oxy-based solid electrolyte, so as to achieve the parameters in Table 1.

[0118] Examples 13-14 This application provides a lithium lanthanum zirconium oxy-based solid electrolyte, a composite solid electrolyte membrane, and a solid battery. The preparation method of the lithium lanthanum zirconium oxy-based solid electrolyte, the composite solid electrolyte membrane, and the solid battery differs from that of Example 1 in that the amount of lithium lanthanum zirconium oxy-based solid electrolyte added in step S3 is adjusted to change the mass percentage of lithium lanthanum zirconium oxy-based solid electrolyte in the composite solid electrolyte membrane, so as to achieve the parameters in Table 1.

[0119] Examples 15-16 This application provides a lithium lanthanum zirconium oxy-based solid electrolyte, a composite solid electrolyte membrane, and a solid battery. The difference between the preparation method of the lithium lanthanum zirconium oxy-based solid electrolyte, the composite solid electrolyte membrane, and the solid battery and that of Example 1 is that the thickness of the composite solid electrolyte membrane is changed by adjusting the casting thickness in step S3 to achieve the parameters in Table 1.

[0120] Comparative Example 1 This application provides a comparative example of a lithium lanthanum zirconium oxy-based solid electrolyte, a composite solid electrolyte membrane, and a solid battery. The difference between the preparation method of the lithium lanthanum zirconium oxy-based solid electrolyte, the composite solid electrolyte membrane, and the solid battery and that of Example 1 is that the atmosphere of pulverization and sieving in step S1 is adjusted so that no oxide layer is generated, in order to achieve the parameters in Table 1.

[0121] Comparative Example 2 This application provides a comparative example of a lithium lanthanum zirconium oxy-based solid electrolyte, a composite solid electrolyte membrane, and a solid battery. The difference between the preparation method of the lithium lanthanum zirconium oxy-based solid electrolyte, the composite solid electrolyte membrane, and the solid battery and that of Example 1 is that no coating layer is introduced.

[0122] Comparative Example 3 This application provides a comparative example of a lithium lanthanum zirconium oxy-based solid electrolyte, a composite solid electrolyte membrane, and a solid battery. The difference between the preparation method of the lithium lanthanum zirconium oxy-based solid electrolyte, the composite solid electrolyte membrane, and the solid battery and that of Example 1 is that calcium oxide is used instead of calcium fluoride.

[0123] The core diameter D, coating layer thickness T, D / T, oxide layer thickness h, average calcium fluoride particle size R, CaF2 mass percentage W1 based on the total mass of the lithium lanthanum zirconium oxy-coated solid electrolyte, lithium lanthanum zirconium oxy-coated solid electrolyte mass percentage W2 based on the total mass of the composite solid electrolyte, and the thickness H and Y of the composite solid electrolyte membrane in each embodiment and comparative example are shown in Table 1.

[0124] Table 1 The performance of the lithium lanthanum zirconium oxy-based solid electrolyte, composite solid electrolyte, and solid battery prepared in the examples and comparative examples is shown in Table 2; the test methods include the following steps: 1) Ionic conductivity testing: The ionic conductivity of the prepared composite solid electrolyte membrane was tested using electrochemical impedance spectroscopy (EIS) with a stainless steel blocking electrode (SS|composite solid electrolyte membrane|SS). The frequency range was 0.1 Hz-1 MHz, and the amplitude was 10 mV. The formula for calculating ionic conductivity (σ) is: σ = L / (R×A), where L is the thickness of the composite solid electrolyte membrane, R is the volume resistance, and A is the effective contact area between the composite solid electrolyte membrane and the stainless steel blocking electrode.

[0125] 2) Interface impedance test: The impedance of the interface between the composite solid electrolyte membrane and the lithium metal anode is tested. Specifically, a lithium metal symmetric battery (Li|composite electrolyte|Li) is assembled, and the interface impedance (R) is measured by EIS with a frequency range of 0.1Hz-1MHz and an amplitude of 10mV.

[0126] 3) Lithium dendrite suppression lifetime test: The lithium dendrite suppression lifetime of the composite solid electrolyte membrane was tested, specifically by applying a constant current density of 0.1 mA / cm² in a lithium metal symmetric cell. 2 For each cycle of 1 hour (0.5 hours of charging and discharging), the time when the battery overpotential suddenly drops or short-circuit is recorded as the battery life.

[0127] 4) Cyclic performance test: The prepared solid-state battery is subjected to a cycle performance test, specifically by cycling at a current density of 0.5C and calculating the capacity retention rate after 300 cycles.

[0128] Table 2 As can be seen from Table 2, when the technical solution provided in this application is adopted, the obtained composite solid electrolyte membrane has excellent comprehensive performance, and the solid battery subsequently prepared also has excellent cycle performance; specifically, the obtained composite solid electrolyte membrane has an ionic conductivity of more than 0.63 mS / cm, an interfacial impedance with the lithium metal anode of less than 126Ω, a lithium dendrite suppression lifetime of more than 1123h, and a cycle capacity retention rate of more than 84% for the obtained solid battery. As can be seen from the examples and comparative examples 1-2, when no oxide layer or coating layer is introduced, the ionic conductivity of the obtained composite solid electrolyte membrane decreases significantly, the interfacial impedance with the lithium metal anode increases significantly, the lithium dendrite suppression lifetime is also shortened significantly, and the cycle capacity retention rate of the obtained solid battery also decreases significantly. As can be seen from the examples and comparative example 3, when it is not calcium fluoride as described in this application, the obtained composite solid electrolyte membrane and the corresponding solid battery cannot achieve the effects of this application.

[0129] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of this application and not to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.

Claims

1. A lithium lanthanum zirconium oxide solid state electrolyte characterized by, The lithium lanthanum zirconium oxide-based solid electrolyte comprises an LLZO core, an oxidation layer arranged on at least part of a surface of the core, and a cladding layer arranged on at least part of a surface of the oxidation layer. The oxidation layer comprises Li2CO3. The cladding layer comprises CaF2.

2. The lithium lanthanum zirconium oxide solid state electrolyte of claim 1, wherein, The lithium lanthanum zirconium oxide-based solid electrolyte satisfies 1≤D / T≤200. D nm is a diameter of the core; T nm is a thickness of the cladding layer.

3. The lithium lanthanum zirconium oxide solid state electrolyte of claim 2, wherein, The diameter D nm of the core is 100-5000; And / or, the thickness T nm of the cladding layer is 10-500.

4. The lithium lanthanum zirconium oxide solid state electrolyte of claim 1, wherein, The thickness of the oxidation layer is 2-20 nm; And / or, a mass percentage of the CaF2, based on a total mass of the lithium lanthanum zirconium oxide-based solid electrolyte, is 5-90%; And / or, an average particle size of the CaF2 is 5-200 nm.

5. A composite solid-state electrolyte, characterized by, The composite solid electrolyte comprises the lithium lanthanum zirconium oxide-based solid electrolyte according to any one of claims 1-4.

6. The composite solid-state electrolyte of claim 5, wherein, A mass percentage of the lithium lanthanum zirconium oxide-based solid electrolyte, based on a total mass of the composite solid electrolyte, is 30-70%; And / or, the composite solid electrolyte further comprises a lithium salt and a polymer matrix.

7. An electrochemical device, characterized by The electrochemical device comprises a positive electrode sheet, a negative electrode sheet, and a composite solid electrolyte film, the composite solid electrolyte film comprising the composite solid electrolyte according to any one of claims 5-6.

8. The electrochemical device of claim 7, wherein, The electrochemical device satisfies 2≤Y≤400; Y=(H×T) / R; H μm is a thickness of the composite solid electrolyte film; T nm is a thickness of the cladding layer; R nm is an average particle size of the CaF2.

9. The electrochemical device of claim 8, wherein, The thickness of the composite solid electrolyte film is 1-30 μm.

10. An electrical device, characterized by The electric device comprises the electrochemical device according to any one of claims 7-9.

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