Multi-element interface-stable high-voltage all-solid-state battery cathode material, preparation method, and electrochemical device

Abstract

A multi-element interface-stabilized high-voltage all-solid-state battery cathode material, preparation method, and electrochemical device, the cathode material comprising a core and a doped layer located on the surface of the core, wherein the core is a lithium-containing layered oxide and the doped layer is a perovskite-like multi-element high-entropy oxide interface layer. The cathode material has a perovskite-like high-entropy oxide interface layer, which effectively mitigates interfacial side reactions between the cathode material and the solid electrolyte, suppresses volume changes in the cathode material during charge and discharge, reduces the risk of poor contact at the solid-solid interface on the cathode side, improves the cycling performance of the cathode material, and thus enhances the stability of the cathode interface. Simultaneously, the interface layer mitigates the irreversible phase transition and lattice oxygen loss of the cathode material during high-voltage cycling, increases the upper cutoff voltage of the cathode material, and realizes an all-solid-state battery with high specific energy and long cycle life.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular to a multi-element interface-stabilized high-voltage all-solid-state battery positive electrode material, a preparation method, and an electrochemical device. Background Art

[0002] In recent years, driven by energy demands and environmental protection requirements, the design and manufacture of chemical power sources with high energy storage capacity and high safety has become a highly sought-after research topic in the new century. Lithium-ion batteries, due to their excellent performance, play a vital role in consumer electronics, electric vehicles, aerospace, and other fields. However, traditional liquid lithium-ion batteries have numerous drawbacks in terms of energy density, safety, and environmental friendliness.

[0003] In contrast, all-solid-state batteries based on metallic lithium negative electrodes have attracted much attention due to their high safety and high energy density, and have become a current research hotspot. However, all-solid-state batteries still face some key problems in practical applications, such as two difficulties: serious interfacial reactions and poor interfacial contact between the positive electrode material and the solid electrolyte, which affect the performance of all-solid-state batteries. Researchers suppress interfacial side reactions and mechanical stability by surface coating and element doping of the positive electrode. However, traditional surface coatings and single element doping are difficult to match the volume changes and irreversible phase changes of the positive electrode material during high-voltage cycling, and have limited inhibitory effects on the escape of positive electrode lattice oxygen.

[0004] It should be noted that the information disclosed in the above background technology section is only used to understand the background of this application, and therefore may include information that does not constitute prior art known to ordinary technicians in this field. Summary of the Invention

[0005] The main purpose of the present invention is to solve at least one of the above technical problems and provide a multi-element interface stable high-voltage all-solid-state battery positive electrode material, a preparation method and an electrochemical device.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] In the first aspect of the present invention, a multi-element interface-stabilized high-voltage all-solid-state battery positive electrode material is provided, which comprises a core and a doping layer located on the surface of the core, wherein the core is a lithium-containing layered oxide, and the doping layer is a multi-element high-entropy oxide interface layer of a perovskite-like phase.

[0008] In some optional embodiments, the doping layer contains doping elements, and the doping elements include at least five of La, Ca, Mg, Lu, Eu, Al, Mo, Ta, Ti, V, Cr, Fe, Cu, Zn, Zr and Nb.

[0009] In some optional embodiments, the doping elements are composed of La, Ca, Mg, Lu and Eu; the molar amount of each element in the doping elements is 5% to 20% of the molar amount of lithium element in the core.

[0010] In some optional embodiments, the thickness of the doping layer is 20 nm to 30 nm.

[0011] In a second aspect of the present invention, a method for preparing a multi-element interface-stabilized high-voltage all-solid-state battery cathode material comprises the following steps:

[0012] dissolving a doping metal source in water or an organic reagent to obtain a precursor solution, wherein the doping metal source includes a doping element;

[0013] Adding lithium-containing positive electrode particles to the precursor solution and mixing to generate solid particles, which are then dried to obtain a powder material; and

[0014] The powder material is sintered to obtain the multi-element interface-stabilized high-voltage all-solid-state battery positive electrode material, wherein in the multi-element interface-stabilized high-voltage all-solid-state battery positive electrode material, the doping element is located on the surface of the lithium-containing positive electrode particles to form a doping layer, and the doping layer is a multi-element high-entropy oxide interface layer of a perovskite-like phase.

[0015] In some optional embodiments, the doping elements include at least five of La, Ca, Mg, Lu, Eu, Al, Mo, Ta, Ti, V, Cr, Fe, Cu, Zn, Zr and Nb.

[0016] In some optional embodiments, the doping element consists of La, Ca, Mg, Lu and Eu;

[0017] The molar amount of each element in the doping element is 5% to 20% of the molar amount of the lithium element in the core.

[0018] In some optional embodiments, in the step of adding the lithium-containing positive electrode particles to the precursor solution and mixing them, the mixing temperature is 25° C. to 100° C., and the mixing time is 6 h to 24 h.

[0019] In some optional embodiments, the sintering heating rate is 1°C / min to 5°C / min, the sintering temperature is 400°C to 800°C, the sintering time is 4h to 8h, and the sintering atmosphere is an oxygen atmosphere.

[0020] In the third aspect of the present invention, an electrochemical device includes a positive electrode plate, a negative electrode plate and a solid electrolyte, wherein the positive electrode plate includes a positive electrode material, and the positive electrode material is the multi-element interface-stabilized high-voltage all-solid-state battery positive electrode material as described above.

[0021] The present invention has the following beneficial effects:

[0022] The present invention provides a multi-element interface-stabilized high-voltage all-solid-state battery positive electrode material, and its preparation method and application. The positive electrode material includes a core and a doped layer located on the surface of the core, wherein the core is a lithium-containing layered oxide and the doped layer is a multi-element high-entropy oxide interface layer. The positive electrode material has a perovskite-like high-entropy oxide interface layer, which effectively alleviates the interface side reactions between the positive electrode material and the solid electrolyte, inhibits the volume change of the positive electrode material during the charge and discharge process, reduces the risk of poor contact of the solid-solid interface on the positive electrode side, improves the cycle performance of the positive electrode material, and thus enhances the stability of the positive electrode interface. At the same time, the interface layer alleviates the irreversible phase change and lattice oxygen loss of the positive electrode material during the high-voltage cycle process, increases the upper cutoff voltage of the positive electrode material, and realizes an all-solid-state battery with high specific energy and long cycle life.

[0023] Compared to the prior art, the multi-element interface-stabilized high-voltage all-solid-state battery positive electrode material provided by the present invention has a doped layer, which is a multi-element high-entropy oxide interface layer of a perovskite-like phase, with high electronic conductivity and low oxygen ion conductivity, which can serve as the oxygen ion buffer layer of the kernel, alleviating the escape of lattice oxygen on the surface of the positive electrode material during charge and discharge, and helping to enhance the interface stability between the positive electrode material and the solid electrolyte. By increasing the entropy value of the interface layer, the interface side reaction between the positive electrode material and the solid electrolyte is effectively alleviated, while suppressing the volume change of the positive electrode material during charge and discharge, reducing the risk of poor contact of the solid-solid interface on the positive electrode side, and improving the cycle performance of the positive electrode material, thereby enhancing the stability of the positive electrode interface of the electrochemical device (such as an all-solid-state battery).

[0024] Other beneficial effects of the embodiments of the present invention will be further described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a process flow chart of a method for preparing a multi-element interface-stabilized high-voltage all-solid-state battery positive electrode material provided in an embodiment of the present application.

[0026] Figure 2 1 and 2. These are the XRD patterns of the positive electrode materials prepared in Example 1, Example 2, and Comparative Example 1 of the present application.

[0027] Figure 3AThis is a comparison chart of the long cycle performance of all-solid-state batteries based on Li3InCl6 solid electrolyte at 0.5C for the positive electrode materials prepared in Example 1, Example 2 and Comparative Example 1 of the present application.

[0028] Figure 3B This is a comparison chart of the long cycle performance of the all-solid-state battery based on Li3InCl6 solid electrolyte at 0.5C for the positive electrode materials prepared in Example 3 of the present application and Comparative Example 2.

[0029] Figure 4A This is a comparison chart of the rate performance of all-solid-state batteries based on Li3InCl6 solid electrolyte, the positive electrode materials prepared in Example 1, Example 2, Comparative Example 1 and Comparative Example 3 of the present application.

[0030] Figure 4B This is a comparison chart of the rate performance of all-solid-state batteries based on Li3InCl6 solid electrolyte, the positive electrode materials prepared in Example 3 and Comparative Example 2 of the present application.

[0031] Figure 5 This is a comparison chart of the high-voltage cycling performance of all-solid-state batteries based on Li3InCl6 solid electrolyte and the positive electrode materials prepared in Example 1 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0032] The following is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is only exemplary and is not intended to limit the scope of the present invention and its application.

[0033] It should be noted that the present invention is based on the following findings: The inventors discovered that bulk doping of a single element in the cathode material has limited effectiveness in suppressing interfacial side reactions and can result in a loss of cathode material capacity. Furthermore, surface coating of the cathode is difficult to achieve a completely uniform thin layer, and the coating layer struggles to adapt to volume changes in the cathode material during cycling. Even with bulk doping or surface coating of the cathode material, problems still exist, such as poor solid-solid interface contact, severe side reactions, volume changes in the cathode material during cycling, and poor stability at high voltages.

[0034] An embodiment of the present application provides a multi-element interface-stabilized high-voltage all-solid-state battery positive electrode material, which includes a core and a doping layer located on the surface of the core, wherein the core is a lithium-containing layered oxide and the doping layer is a multi-element high-entropy oxide interface layer of a perovskite-like phase.

[0035] In some embodiments, the lithium-containing layered oxide core can be lithium cobalt oxide and / or a nickel-cobalt-manganese ternary cathode material. These materials are used as cathode core materials in all-solid-state lithium-ion batteries because of their stable structure and good conductivity, ensuring the energy density and safety of all-solid-state lithium-ion batteries. However, these cathode materials can pose serious challenges with solid-state electrolytes, including interfacial reactions, poor contact, and space charge layers.

[0036] To this end, the embodiment of the present application performs multi-element surface high entropy doping on the lithium-containing layered oxide to form a doped layer. The atomic arrangement in the doped layer is random and disordered, resulting in an increase in the configurational entropy of the doped layer and causing lattice distortion. These microstructural features enable the positive electrode material to exhibit excellent performance, such as chemical stability, good cycle performance, rate performance, and high-voltage stability. The doped layer is a perovskite-like phase. This multi-component, structurally stable perovskite-like phase interface layer has high lithium ion conductivity, high electronic conductivity, and low oxygen ion conductivity. It can act as an oxygen ion buffer layer, alleviate the escape of lattice oxygen on the positive electrode surface during charging and discharging, hinder the diffusion of solid electrolyte decomposition byproducts, and help enhance the interface stability between the positive electrode material and the solid electrolyte. In all-solid-state batteries, the interface between the positive electrode material and the solid electrolyte is crucial to battery performance. A stable interface can reduce the polarization and resistance of the battery during charging and discharging, which is beneficial to improving the battery's cycle performance and long-term stability. The interface layer also has a large number of oxygen vacancies, which can prevent the loss of lattice oxygen in the positive electrode material during charging and discharging. At the same time, the interface layer has higher ionic conductivity and electronic conductivity than the layered structure of the inner core, which helps promote the rapid transmission of ions and electrons on the positive electrode side, thereby improving the rate performance of the prepared battery.

[0037] Specifically, the doping elements contained in the doping layer may include at least five of La, Ca, Mg, Lu, Eu, Al, Mo, Ta, Ti, V, Cr, Fe, Cu, Zn, Zr, and Nb. The high-entropy oxide doping layer formed by different doping elements has certain differences in electrochemical properties, and the above doping elements can be selected according to actual needs.

[0038] Among them, La, Lu, Eu, Mo, Ta, Ti, V, Cr, Fe, Cu, Zn, Zr, and Nb are transition metal elements. Doping with these transition metal elements can change the electronic structure and charge transport characteristics of layered oxide cathode materials, thereby improving their electrochemical performance, such as increasing discharge capacity and cycle stability. They can also stabilize the layered structure, inhibiting the structural evolution of the material during cycling and the capacity decay of the electrode material, thereby extending the life of the battery. At the same time, they can fine-tune the lattice parameters and crystal structure of the cathode material, improving the distribution of electrochemically active sites and electrochemical performance of the cathode material. La, Lu, and Eu are all lanthanide elements with similar chemical properties, which is beneficial for enhancing the crystal structure stability of the cathode material and reducing structural defects caused by doping.

[0039] Ca, Mg and Al are non-transition metals. + The presence of elements such as Ca, Mg, and Al in the cathode material can enhance the electronic conductivity of the cathode material and promote rapid electron transport, thereby increasing the energy density and charge / discharge rate of the battery. Furthermore, Ca and Mg are elements of the same family and have similar chemical properties, which helps to enhance the crystal structure stability of the cathode material and reduce structural defects caused by doping.

[0040] Furthermore, the doping elements can be composed of La, Ca, Mg, Lu and Eu. The above five elements are used for doping. Since La, Lu and Eu are all lanthanide elements, and Ca and Mg are also alkaline earth metal elements, they all have similar chemical properties. Together, they complete the construction of the interface structure of the perovskite-like high entropy oxide layer, which is beneficial to enhancing the crystal structure stability of the positive electrode material.

[0041] In some embodiments, the thickness of the doping layer may be 20 nm to 30 nm, further 20 nm to 25 nm, and illustratively may be 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, or 30 nm, etc. Within the above range, the doping layer can effectively stabilize the reaction interface between the positive electrode material and the solid electrolyte.

[0042] In some embodiments, the molar amount of each doping element in the doping layer may be 5% to 20% of the molar amount of the lithium element in the doping layer, for example, 5% to 7% or 12% to 15%, and illustratively, may be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%, etc. Controlling the molar amount of each doping element in the doping layer to be within the range of 5% to 20% of the molar amount of the lithium element can reduce the volume expansion and side effects of chemical reactions of the battery during the charge and discharge process, thereby improving the safety of the battery and extending its service life.

[0043] Furthermore, the molar amounts of each element in the doping element in the doping layer can be similar, and further, the molar amounts of each element in the doping element can be the same. Controlling the molar amounts of each element to be similar or the same can maximize the entropy effect in the material, ensure the random distribution and arrangement of multiple elements in the doping elements, and increase the irregularity of the structure and properties of the doping layer. This irregularity can increase the thermal stability and electrochemical stability of the positive electrode material, and improve the energy density and power density. The doping design with the same molar amount of each element helps to maintain the balance and stability of the material structure, avoid uneven reactions caused by local excess elements, and thus improve the long-term stability and reliability of the battery.

[0044] Compared with the prior art, the multi-element interface-stabilized high-voltage all-solid-state battery cathode material provided by the embodiments of the present application has the following beneficial effects:

[0045] 1. The positive electrode material has a multi-element high-entropy oxide interface layer as a doping layer, which effectively alleviates the interfacial side reactions between the positive electrode material and the solid electrolyte, while suppressing the serious volume change and irreversible phase change of the positive electrode material during high-voltage cycling, reducing the risk of poor contact at the solid-solid interface on the positive electrode side, and improving the high-voltage cycling performance of the positive electrode material, thereby enhancing the stability of the positive electrode interface of electrochemical devices (such as all-solid-state batteries).

[0046] 2. By doping with multiple elements and controlling the content of the doping elements, the entropy value of the doping layer is further increased, a high-entropy oxide interface layer is constructed, which ensures the interface stability between the positive electrode and the solid electrolyte, significantly improves the cycle performance of the all-solid-state battery, and provides a new idea for the interface modification of all-solid-state batteries.

[0047] 3. The doped layer is a perovskite-like phase, which has high ionic and electronic conductivity and low oxygen ion conductivity. It can act as an oxygen ion buffer layer, alleviating the escape of lattice oxygen on the positive electrode surface during charging and discharging, hindering the diffusion of decomposition byproducts of the solid electrolyte layer, and helping to enhance the interface stability between the positive electrode material and the solid electrolyte.

[0048] See also Figure 1As shown, the embodiment of the present application provides a method for preparing a multi-element interface-stabilized high-voltage all-solid-state battery positive electrode material, which specifically includes the following steps:

[0049] Step S1, dissolving a doping metal source in water or an organic reagent to obtain a precursor solution, wherein the doping metal source includes a doping element.

[0050] Specifically, a doping metal source is weighed and dissolved in deionized water or an organic reagent according to a certain molar ratio, and stirred to fully dissolve to obtain a precursor solution. The doping metal source contains doping elements, and the doping elements may include at least five of La, Ca, Mg, Lu, Eu, Al, Mo, Ta, Ti, V, Cr, Fe, Cu, Zn, Zr, and Nb. An appropriate amount of transition metal elements (such as L a The layered oxide cathode material can be doped with La, Ca, Mg, Lu, and Eu) and non-transition metal elements (Ca, Al, and Mg). Further, the doping elements can be composed of La, Ca, Mg, Lu, and Eu.

[0051] In some embodiments, the doping metal source can be a chloride of the doping element. The chloride of the doping element has good solubility in water or organic solvents, can provide stable doping metal ions, and these metal ions can be evenly dispersed in the solution, which is beneficial to the uniformity and efficiency of subsequent reactions.

[0052] In some embodiments, the organic reagent may include one of anhydrous ethanol and N,N-dimethylacetamide (DMF). These organic reagents all have good solubility and can effectively dissolve the doping metal source to form a uniform solution. For example, DMF has good solubility and is particularly suitable for dissolving metal salts. It can also provide relatively mild reaction conditions, which is conducive to controlling factors such as temperature and solution pH during the doping process, thereby avoiding unnecessary structural damage to the material or side effects of chemical reactions.

[0053] In step S2, lithium-containing positive electrode particles are added to the precursor solution, mixed, and the upper clear liquid is filtered off to obtain solid particles, which are then dried to obtain a powder material.

[0054] Specifically, a certain amount of lithium-containing positive electrode particles is added to the mixed solution obtained in step S1, the mixed solution is heated, fully mixed at a certain temperature, and a liquid-phase ion exchange reaction is carried out. After the ion exchange reaction is completed, the obtained reaction product is subjected to solid-liquid separation, the upper clear liquid is filtered out, and the retained solid particles are washed with deionized water, and then dried in a blast oven at 80-100°C to obtain a powder material. The filtered upper clear liquid contains the unreacted mixed solution and newly generated LiCl, and the obtained powder material is the doped positive electrode material. It can be understood that the method of heating the mixed solution includes but is not limited to an oil bath, a water bath or a metal bath, and any method that can achieve uniform heating of the solution is acceptable.

[0055] In some embodiments, the lithium-containing positive electrode particles can be lithium cobalt oxide positive electrode or nickel-cobalt-manganese ternary positive electrode, etc.

[0056] Ion exchange reaction refers to the lithium ion (Li + ) and metal ions in the precursor solution (such as La 3+ , Ca 2+ Mg 2+ 、Lu 3+ 、Eu 3+ 、Al 3+ and Mo 6+ For example, lithium cobalt oxide is used as the lithium-containing positive electrode particle, and the reaction can be expressed as follows:

[0057] LiCoO2+MCl x →MCoO2+LiCl

[0058] Where M represents the metal ion in the solution and x represents the coordination number in the corresponding compound.

[0059] In some embodiments, the mixing temperature can be 25°C to 100°C, and further can be 70°C to 90°C. For example, it can be 25°C, 35°C, 50°C, 70°C, 80°C, 90°C or 100°C, etc. Under the above temperature conditions, it is beneficial to increase the reaction rate, accelerate the diffusion of ions and the reaction.

[0060] In some embodiments, the mixing time can be 6 hours to 24 hours, and can further be 12 hours to 24 hours. For example, it can be 6 hours, 9 hours, 12 hours, 15 hours, 18 hours, 21 hours or 24 hours. Within the above time range, sufficient time can be guaranteed for the ion exchange reaction to ensure the effective replacement of lithium ions in the lithium-containing positive electrode particles with metal ions in the precursor solution.

[0061] In some embodiments, the molar amount of each component in the doping element is 5% to 20% of the molar amount of lithium in the lithium-containing positive electrode particles, for example, it can be 5% to 7% or 12% to 15%, and illustratively, it can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, etc. Controlling the molar amount of the doping element in the doping metal source in step S1 to be within the range of 5% to 20% of the molar amount of the lithium element can ensure that the doping element effectively replaces the lithium element in the lithium-containing positive electrode particles, reducing the volume expansion, irreversible phase change and side decomposition reaction of the battery during high-voltage cycling, thereby improving the safety of the battery and extending its service life; it can also effectively improve the electrochemical properties of the positive electrode material, such as increasing the energy density, discharge capacity and cycle stability.

[0062] Furthermore, the molar amount of each element in the doping element can be the same. Similar element contents can increase the irregularity of the structure and properties of the doping layer, thereby increasing the entropy value of the doping layer.

[0063] In step S3, the powder material is sintered to obtain a multi-element interface-stable high-voltage all-solid-state battery positive electrode material, wherein in the positive electrode material, the doping elements are located on the surface of the lithium-containing positive electrode particles to form a doping layer, and the doping layer is a multi-element high-entropy oxide interface layer of a perovskite-like phase.

[0064] Specifically, the dried powder material is placed in a heating device (such as a tubular atmosphere furnace), sintered under certain sintering conditions in an oxygen atmosphere, and then cooled to room temperature to obtain a surface high-entropy doped positive electrode material.

[0065] In some embodiments, the sintering heating rate is 1°C / min to 5°C / min, and further can be 2°C / min to 4°C / min, and can be 1°C / min, 1.5°C / min, 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, 4°C / min, 4.5°C / min, or 5°C / min, etc. During the sintering process, an appropriate heating rate can reduce thermal stress caused by temperature gradients in the material during the heating process and help promote reaction uniformity and diffusion of substances.

[0066] In some embodiments, the sintering temperature is 500°C to 700°C, and can further be 550°C to 650°C, and can be 500°C, 550°C, 600°C, 650°C or 700°C, for example. The above temperature range is conducive to the reaction and diffusion of the doping elements and the lithium-containing positive electrode particles, forming a uniform perovskite-like high-entropy doped metal oxide layer on the surface of the positive electrode material, and helping to ensure the structural stability of the positive electrode material and the progress of phase change.

[0067] In some embodiments, the sintering time is 4 to 8 hours, and further can be 5 to 7 hours, and illustratively can be 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours, etc. Sufficient time can ensure that the doping element is fully diffused and reacts with the lithium-containing positive electrode particles to form a high-entropy oxide interface layer.

[0068] In some embodiments, the sintering atmosphere is an oxygen atmosphere, which can provide a sufficiently oxidizing environment, help promote the oxidation reaction, maintain the stability and uniformity of oxygen in the material, and thus ensure the formation of the doping layer and the stability of the material structure.

[0069] Compared with the prior art, the method for preparing a multi-element interface-stabilized high-voltage all-solid-state battery cathode material provided in the embodiments of the present application has the following beneficial effects:

[0070] 1. By using a variety of metal elements to perform high-entropy doping on layered oxide cathode materials, a cathode material with a high-entropy doped structure on the surface of a perovskite-like phase is obtained, which effectively alleviates the interfacial side reactions between the cathode material and the solid electrolyte, and at the same time inhibits the severe volume change and irreversible phase change of the cathode material during high-voltage cycling, reduces the risk of poor solid-solid contact on the cathode side, and improves the stability of the cathode interface of the all-solid-state battery prepared with the cathode material.

[0071] 2. The liquid phase ion exchange method is used to prepare the positive electrode material, and the molar ratio of each doping element to the lithium element is adjusted at the same time to allow a full replacement reaction to occur. This method has high uniformity and ensures that the elements are uniformly doped into the positive electrode material by controlling the reaction conditions in the solution; it has strong controllability and can precisely control the reaction conditions, including solution concentration and temperature; the reaction speed is fast, which is conducive to the efficient doping of doping elements.

[0072] 3. The preparation method has simple process, low cost, and easy control of the production process, and is suitable for large-scale industrial production of positive electrode materials.

[0073] The present application also provides an electrochemical device (e.g., a solid-state battery) comprising a positive electrode sheet, a negative electrode sheet, and a solid-state electrolyte. The positive electrode sheet comprises a positive electrode material, which is a multi-element interface-stabilized high-voltage all-solid-state battery positive electrode material as described above. Due to the advantages of good chemical / electrochemical stability, good rate performance, and structural stability, this positive electrode material improves the safety, cycle life, and rate performance of lithium-ion batteries at high voltages.

[0074] The following is a further description of the aforementioned multi-element interface-stabilized high-voltage all-solid-state battery positive electrode material and its preparation method through specific examples.

[0075] Example 1

[0076] Step 1: Weigh a certain amount of metal chlorides (LaCl3, CaCl2, MgCl2, LuCl3, and EuCl3) in equal molar ratios and add them to 5 mL of deionized water. Stir to fully dissolve them to obtain a precursor solution in which the ion concentration of each element is 0.2 mol / L.

[0077] Step 2: Add 1 g of lithium cobalt oxide positive electrode material to the precursor solution obtained in step 1, heat it in an oil bath, and perform ion exchange reaction at 90°C for 24 hours. The reaction product is separated into solid and liquid, and the solid particles are washed with deionized water. Then, the solid particles are dried in a blast oven at 80°C to obtain a powder material.

[0078] Step 3: Place the powder material obtained in step 2 into a tubular atmosphere furnace, heat it to 600°C at a heating rate of 5°C / min in an oxygen atmosphere, and calcine it for 6 hours, then cool it to room temperature to obtain a surface high entropy doped lithium cobalt oxide positive electrode material (HE-LCO-90°C).

[0079] Example 2

[0080] Step 1: Weigh a certain amount of metal chlorides (LaCl3, CaCl2, MgCl2, LuCl3, and EuCl3) in equal molar ratios and add them to 5 mL of deionized water. Stir to fully dissolve them to obtain a precursor solution in which the ion concentration of each element is 0.2 mol / L.

[0081] Step 2: Add 1 g of lithium cobalt oxide positive electrode material to the precursor solution obtained in step 1, carry out ion exchange reaction at a temperature of 25°C for 24 hours, perform solid-liquid separation on the reaction product, and wash the solid particles with deionized water. Then, dry them in a blast oven at 80°C to obtain a powder material.

[0082] Step 3: Place the powder material obtained in step 2 into a tubular atmosphere furnace, heat it to 600°C at a heating rate of 5°C / min in an oxygen atmosphere, and calcine it for 6 hours, then cool it to room temperature to obtain a surface high entropy doped lithium cobalt oxide positive electrode material (HE-LCO-25°C).

[0083] Example 3

[0084] Step 1: Weigh a certain amount of metal chlorides (LaCl3, CaCl2, MgCl2, LuCl3 and EuCl3) in an equimolar ratio and add them to 5 mL of DMF solvent, stirring to fully dissolve them to obtain a precursor solution, in which the ion concentration of each element is 0.2 mol / L.

[0085] Step 2: 1gLiNi 0.8 Co 0.1 Mn0.1 The O2 positive electrode material was added to the precursor solution obtained in step 1, and the ion exchange reaction was carried out at a temperature of 25°C for 24 hours. The reaction product was subjected to solid-liquid separation, and the solid particles were washed with a DMF solvent. Then, the solid particles were dried in a blast oven at 80°C to obtain a powder material.

[0086] Step 3: The powder material obtained in step 2 was placed in a tubular atmosphere furnace, heated to 600°C at a heating rate of 5°C / min in an oxygen atmosphere, and calcined for 6 hours, and then cooled to room temperature to obtain surface high entropy doped LiNi 0.8 Co 0.1 Mn 0.1 O2 positive electrode material (HE-NCM811).

[0087] Comparative Example 1

[0088] Step 1: Add 1 g of lithium cobalt oxide positive electrode material to deionized water, heat it in an oil bath, stir it at 90°C for 24 hours, perform solid-liquid separation on the reaction product, wash the solid particles with deionized water, and then dry them in a blast oven at 80°C to obtain a powder material.

[0089] Step 2: Place the powder material obtained in step 1 into a tubular atmosphere furnace, heat it to 600°C at a heating rate of 5°C / min in an oxygen atmosphere, and calcine it for 6 hours, then cool it to room temperature to obtain an undoped lithium cobalt oxide positive electrode material (Bare-LCO).

[0090] Comparative Example 2

[0091] Step 1: 1g LiNi 0.8 Co 0.1 Mn 0.1 The O2 positive electrode material was added to the DMF solvent and stirred at 25°C for 24 hours. The reaction product was subjected to solid-liquid separation. The solid particles were washed with DMF solvent and then dried in a blast oven at 80°C to obtain a powder material.

[0092] Step 2: The powder material obtained in step 1 was placed in a tubular atmosphere furnace, heated to 600°C at a heating rate of 5°C / min in an oxygen atmosphere, and calcined for 6 hours, and then cooled to room temperature to obtain undoped LiNi 0.8 Co 0.1 Mn 0.1 O2 positive electrode material (Bare-NCM811).

[0093] Comparative Example 3

[0094] Step 1: Weigh a certain amount of metal chlorides (LaCl3 and CaCl2) in an equimolar ratio and add them to 5 mL of deionized water. Stir to fully dissolve them to obtain a precursor solution in which the ion concentration of each element is 0.2 mol / L.

[0095] Step 2: Add 1 g of lithium cobalt oxide positive electrode material to the precursor solution obtained in step 1, carry out ion exchange reaction at a temperature of 25°C for 24 hours, perform solid-liquid separation on the reaction product, and wash the solid particles with deionized water. Then, dry them in a blast oven at 80°C to obtain a powder material.

[0096] Step 3: Place the powder material obtained in step 2 into a tubular atmosphere furnace, heat it to 600°C at a heating rate of 5°C / min in an oxygen atmosphere, and calcine it for 6 hours, then cool it to room temperature to obtain La and Ca element-doped lithium cobalt oxide positive electrode material (LCO-LaCa).

[0097] Comparative testing

[0098] The following tests were performed on the positive electrode materials obtained in Examples 1-3 and Comparative Examples 1-3, and corresponding test results were obtained.

[0099] 1. X-ray diffraction tests were performed on Example 1, Example 2 and Comparative Example 1. The results are as follows: Figure 2 Comparative analysis of the results shows that the XRD patterns of Example 1, Example 2 and Comparative Example 1 are consistent, indicating that the addition of doping metal elements does not change the structure of the lithium cobalt oxide material.

[0100] 2. The positive electrode materials obtained in Examples 1-3 and Comparative Examples 1-3 were used to prepare all-solid-state batteries and perform electrochemical tests:

[0101] According to the mass ratio of positive electrode material: lithium indium chlorine solid electrolyte = 70:30, manual grinding for 10 minutes is made into a mixed positive electrode powder, which is then installed into a solid-state mold battery. The specific process of solid-state battery installation is as follows: 80mg of solid electrolyte powder is placed in a battery mold with a diameter of 10mm and pressed under a pressure of 1t. Then 10mg of positive electrode composite powder is added to one side of the LIC particle and pressed at a pressure of 3.5t. Finally, a piece of Li-In foil is placed on the other side of the LIC particle and pressed at a pressure of 0.5t. In order to avoid In 3+ The possible effect of redox conversion between Li and In is to add Li between the Li-In negative electrode and the solid electrolyte. 10 GeP2S 12 The electrochemical performance of the assembled solid-state battery was tested at 25°C.

[0102] (1) The batteries prepared with the positive electrode materials in Examples 1-3 and Comparative Examples 1-2 were subjected to a long cycle test at a rate of 0.5C. The results are as follows: Figure 3A and Figure 3B shown.

[0103] Long-cycle performance test method: At room temperature (25°C), the battery is charged and discharged at a current density of 0.5C in the charge and discharge range of 3.0 to 4.3V to obtain the battery's specific capacity and coulombic efficiency. The lithium-ion battery is charged to 4.3V at a constant current of 0.5C (C represents the current rate, 1C = 160mA / g), and the charge capacity is recorded; then discharged at 0.5C to a cut-off voltage of 3.0V, and the discharge capacity is recorded. This cycle is repeated 250 times. The 0.5C specific capacity of the positive electrode material is calculated based on the discharge capacity, and the coulombic efficiency of the battery is calculated according to the following formula: Coulombic efficiency = (discharge capacity / charge capacity) * 100%.

[0104] The results show that in the voltage range of 3-4.3V, 25°C, and 0.5C rate, the batteries prepared with the cathode materials obtained in Examples 1 and 2 exhibited superior cycling stability compared to Comparative Example 1; Example 3 also exhibited superior cycling stability compared to Comparative Example 2. This is because the high-entropy doping layer formed in the cathode materials of Examples 1-3 ensures the interfacial stability between the cathode and the solid electrolyte, significantly improving the cycling performance of the batteries.

[0105] (2) The rate performance of the batteries prepared with the positive electrode materials in Examples 1-3 and Comparative Examples 1-3 was tested. The results are as follows: Figure 4A and Figure 4B shown.

[0106] Rate performance test method: Under normal temperature conditions of 25°C, the battery is charged and discharged at a current density of 0.1C / 0.2C / 0.5C / 1C / 0.1C in the charge and discharge range of 3-4.3V. 5 cycles are performed under each current density condition to obtain the battery's specific capacity and coulombic efficiency. The lithium-ion battery is charged to 4.3V at a constant current of 0.1C / 0.2C / 0.5C / 1C / 0.1C (C represents the current rate, 1C = 160mA / g). Charging is stopped and the charge capacity is recorded; then the battery is discharged at a current density of 0.1C / 0.2C / 0.5C / 1C / 0.1C to a cut-off voltage of 3.0V, and the discharge capacity is recorded. The 0.1C specific capacity of the positive electrode material is calculated based on the first discharge capacity, and the coulombic efficiency of the battery is calculated according to the following formula: Coulombic efficiency = (first discharge capacity / first charge capacity) * 100%.

[0107] Compared to Comparative Examples 1 and 3, the batteries prepared with the cathode materials obtained in Examples 1 and 2 exhibited superior rate performance; compared to Comparative Example 2, Example 3 also exhibited superior rate performance. This is due to the multi-element high-entropy doping of the cathode materials in Examples 1-3, which improved the rate performance of the batteries.

[0108] (3) The battery prepared with the positive electrode materials in Example 1 and Comparative Example 1 was subjected to a high voltage cycle performance test. The results are as follows: Figure 5 shown.

[0109] Test method: Under normal temperature conditions of 25°C, charge the battery to 4.5V at a constant current of 0.5C (C represents the current rate, 1C = 160mA / g), stop charging, and record the charge capacity; then discharge the battery at 0.5C to a cut-off voltage of 3.0V, record the discharge capacity, and calculate the coulombic efficiency of the battery according to the following formula: Coulombic efficiency = (initial discharge capacity / initial charge capacity) * 100%.

[0110] The results show that compared with Comparative Example 1, the battery prepared with the positive electrode material obtained in Example 1 exhibits better high-voltage cycling performance because the perovskite-like high-entropy oxide interface layer of the positive electrode material alleviates the irreversible phase change and lattice oxygen loss of the positive electrode material during high-voltage cycling.

[0111] The above description further details the present invention in conjunction with specific / preferred embodiments, and the specific implementation of the present invention should not be construed as being limited to these descriptions. Persons skilled in the art will appreciate that, without departing from the spirit of the present invention, they may make various substitutions or modifications to the described embodiments, and these substitutions or modifications should be considered to fall within the scope of protection of the present invention. Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "preferred embodiments," "examples," "specific examples," or "some examples" indicates that the specific features, structures, materials, or characteristics described in conjunction with such embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Persons skilled in the art may combine and assemble the different embodiments or examples described in this specification, as well as features of different embodiments or examples, without conflicting opinions. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications may be made herein without departing from the scope of protection of the patent application.

Claims

1. A multi-element interface-stable high-voltage all-solid-state battery cathode material, characterized in that: The invention comprises a core and a doping layer located on the surface of the core, wherein the core is a lithium-containing layered oxide, the doping layer is a multi-element high-entropy oxide interface layer of a perovskite-like phase, and the doping layer contains doping elements, which are composed of La, Ca, Mg, Lu and Eu; the molar amount of each element in the doping elements is 5% to 20% of the molar amount of lithium in the lithium-containing layered oxide.

2. The multi-element interface-stabilized high-voltage all-solid-state battery cathode material according to claim 1, characterized in that: The thickness of the doping layer is 20nm-30nm.

3. A method for preparing a multi-element interface-stable high-voltage all-solid-state battery cathode material, characterized in that: include: Dissolving a plurality of doping metal sources in water or an organic reagent to obtain a precursor solution, wherein the doping metal sources comprise doping elements; the doping elements are composed of La, Ca, Mg, Lu, and Eu, and the molar amount of each doping element is 5% to 20% of the molar amount of lithium in the lithium-containing layered oxide; Adding the lithium-containing layered oxide to the precursor solution and mixing to generate solid particles, which are then dried to obtain a powder material; and The powder material is sintered to obtain the multi-element interface-stabilized high-voltage all-solid-state battery positive electrode material, wherein in the multi-element interface-stabilized high-voltage all-solid-state battery positive electrode material, the doping element is located on the surface of the lithium-containing layered oxide to form a doping layer, and the doping layer is a multi-element high-entropy oxide interface layer of a perovskite-like phase.

4. The method for preparing a multi-element interface-stabilized high-voltage all-solid-state battery cathode material according to claim 3, characterized in that: In the step of adding the lithium-containing layered oxide to the precursor solution and mixing them, the mixing temperature is 25° C. to 100° C., and the mixing time is 6 h to 24 h.

5. The method for preparing a multi-element interface-stabilized high-voltage all-solid-state battery cathode material according to any one of claims 3 to 4, characterized in that: The sintering temperature rise rate is 1°C / min~5°C / min, the sintering temperature is 400°C~800°C, the sintering time is 4h~8h, and the sintering atmosphere is an oxygen atmosphere.

6. An electrochemical device, characterized in that The electrochemical device includes a positive electrode plate, a negative electrode plate and a solid electrolyte, wherein the positive electrode plate includes a positive electrode material, and the positive electrode material is a multi-element interface-stabilized high-voltage all-solid-state battery positive electrode material as described in any one of claims 1 to 2 or a positive electrode material prepared by the preparation method of the multi-element interface-stabilized high-voltage all-solid-state battery positive electrode material as described in any one of claims 3 to 5.

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