Fast ion conductor-carbon synergistically coated ternary positive electrode material and preparation method thereof, battery and electric equipment

Abstract

The invention provides a fast ion conductor-carbon synergistically coated ternary positive electrode material and a preparation method thereof, a battery and electric equipment, and relates to the technical field of batteries. The fast ion conductor-carbon synergistically coated ternary positive electrode material comprises an inner core and a composite coating layer, the inner core is a ternary positive electrode material, the chemical general formula of the ternary positive electrode material is LiNi < x > Mn < y > Co < z > O < 2 >, and the composite coating layer is composed of NASICON type fast ion conductor nanocrystals and amorphous carbon; the chemical general formula of the NASICON type fast ion conductor nanocrystal is LiM2 (PO4) 3, wherein M is one or more of Ti, Zr and Ge. According to the fast ion conductor-carbon synergistically coated ternary positive electrode material provided by the invention, an ion-electron double-conduction network is constructed, and the dynamic bottleneck is solved; mechanical contact failure is inhibited through tough interface combination; the chemical stability is excellent, and the interface side reaction is blocked.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a fast ion conductor-carbon co-coated ternary cathode material and its preparation method, battery and electrical equipment. Background Technology

[0002] Layered ternary oxide cathode materials are key to achieving high-energy-density lithium-ion batteries. However, when matched with solid-state electrolytes, especially sulfide solid-state electrolytes, to construct all-solid-state batteries, they face severe interfacial compatibility challenges. Sulfide solid-state electrolytes possess excellent mechanical ductility and high ionic conductivity comparable to liquid electrolytes, making them one of the most promising electrolyte materials for achieving high-energy-density all-solid-state batteries. However, the main problems that urgently need to be solved in the application of ternary cathode materials in solid-state batteries are as follows: 1. Severe interfacial side reactions and space charge layer effect: An electrochemical potential difference exists between the ternary cathode material and the sulfide electrolyte. Direct contact easily leads to the formation of a space charge layer, resulting in uneven lithium-ion distribution and a sharp increase in interfacial contact resistance. Simultaneously, the cathode generates reactive oxygen species under high-voltage charging conditions. These reactive oxygen species undergo violent interfacial side reactions with the sulfide electrolyte, generating substances such as Li₂S and P₂S. x A high-impedance interface layer can reduce the electrolyte interface conductivity by several orders of magnitude, severely degrading battery performance.

[0003] 2. Mechanical contact failure during cycling: Ternary materials undergo irreversible phase transitions during lithium-ion insertion and extraction, causing repeated expansion and contraction of the cell volume. While sulfide electrolytes have some flexibility, they are still relatively rigid and cannot perfectly accommodate this dynamic volume change, resulting in fewer solid-solid contact points and broken ion transport channels. This not only leads to a continuous increase in interfacial impedance but also causes excessively high local current density, triggering lithium dendrite growth and other problems, severely impairing the battery's cycle life and safety.

[0004] 3. Traditional inorganic coatings introduce new performance bottlenecks: To isolate side reactions, coating with traditional oxides such as Al2O3 and MgO is a common strategy. However, these coating materials have zero intrinsic ionic conductivity, severely hindering lithium-ion interfacial transport, significantly reducing battery kinetic performance, and affecting rate performance and capacity utilization. More importantly, these coatings typically only have physical adsorption bonding with the cathode substrate, resulting in weak interfacial adhesion. Under long-term cycling and volume change stress, the coating is prone to cracking and peeling off from the substrate, causing the protected active material to be re-exposed and accelerate its degradation, leading to a sharp drop in capacity retention.

[0005] In summary, developing a novel coating layer that can efficiently conduct lithium ions, firmly bond with the cathode substrate to suppress side reactions and volume changes, and at the same time not sacrifice interfacial dynamics performance is key to overcoming the bottleneck of ternary materials in solid-state batteries. Summary of the Invention

[0006] The purpose of this application is to provide a fast ion conductor-carbon co-coated ternary cathode material, its preparation method, battery, and electrical device to solve the above-mentioned problems.

[0007] To achieve the above objectives, this application adopts the following technical solution: A fast-ion conductor-carbon co-coated ternary cathode material, comprising a core and a composite coating layer; The core is a ternary cathode material, and the general chemical formula of the ternary cathode material is LiNi. x Mn y Co z O2, where x+y+z=1, and x>0.5, y>0, z>0; The composite coating layer is composed of NASICON-type fast ion conductor nanocrystals and amorphous carbon. The general chemical formula of the NASICON-type fast ion conductor nanocrystal is LiM2(PO4)3, where M is one or more of Ti, Zr, and Ge.

[0008] Preferably, the fast ion conductor-carbon co-coated ternary cathode material satisfies one or more of the following conditions: (1) The thickness of the composite coating layer is 5-20 nm, preferably 10-30 nm; Optionally, the thickness of the composite coating layer can be any value between 5nm, 10nm, 15nm, 20nm, or 5-20nm; (2) The composite coating layer accounts for 0.5%-10% of the total mass of the fast ion conductor-carbon synergistic coating ternary cathode material, preferably 1%-5%; Optionally, the proportion of the composite coating layer to the total mass of the fast ion conductor-carbon co-coated ternary cathode material can be any value between 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or 0.5%-10%. (3) The amorphous carbon accounts for 5%-40% of the total mass of the composite coating layer.

[0009] Optionally, the proportion of amorphous carbon to the total mass of the composite coating layer can be any value between 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or 5%-40%.

[0010] This application also provides a method for preparing the fast ion conductor-carbon co-coated ternary cathode material, comprising: A precursor sol was obtained by mixing a lithium source, an M-source metal salt, a phosphorus source, an organic carbon source, water, and anhydrous ethanol. The ternary cathode material is mixed with the precursor sol and mechanically dispersed to obtain a slurry. The slurry is dried to obtain a dry gel-coated precursor, which is then pre-calcined in air and sintered in an inert atmosphere to obtain the fast ion conductor-carbon co-coated ternary cathode material.

[0011] Preferably, the preparation method of the fast ion conductor-carbon co-coated ternary cathode material satisfies one or more of the following conditions: (1) The lithium source includes lithium nitrate and / or lithium acetate; (2) The M source metal salt includes one or more of tetrabutyl titanate, tetraisopropyl titanate, zirconium oxychloride, and tetraethyl germanate; (3) The phosphorus source includes one or more of phosphoric acid, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate; (4) The organic carbon source includes one or more of citric acid, oxalic acid, sucrose, and polyvinylpyrrolidone, preferably citric acid.

[0012] Preferably, the preparation method of the fast ion conductor-carbon co-coated ternary cathode material satisfies one or more of the following conditions: (1) The amounts of the lithium source, the M source metal salt, and the phosphorus source are measured according to the molar ratio of Li, M, and P as (0.8-1.2):(1.8-2.2):(2.8-3.2); Optionally, the molar ratio of Li, M, and P can be any value between 0.8:1.8:2.8, 1:2:3, 1.2:2.2:3.2, or (0.8-1.2):(1.8-2.2):(2.8-3.2). (2) The total molar ratio of the organic carbon source to the metal ions is (0.8-1.5):1; Optionally, the ratio of the total molar amount of the organic carbon source to the metal ions can be any value between 0.8:1, 1:1, 1.5:1, or (0.8-1.5):1; (3) The volume ratio of the water to the anhydrous ethanol is 1:(2-4); Optionally, the volume ratio of water to anhydrous ethanol can be any value between 1:2, 1:3, 1:4 or 1:(2-4); (4) The ratio of the volume of the precursor sol to the mass of the ternary cathode material is (0.5-2) mL / g.

[0013] Optionally, the ratio of the volume of the precursor sol to the mass of the ternary cathode material can be any value between 0.5 mL / g, 1 mL / g, 1.5 mL / g, 2 mL / g, or (0.5-2) mL / g.

[0014] Preferably, the preparation method of the fast ion conductor-carbon co-coated ternary cathode material satisfies one or more of the following conditions: (1) The mechanical dispersion is ball milling or shear mixing for 0.5-3 hours; Optionally, the mechanical dispersion time can be any value between 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, or 0.5-3h; (2) The drying temperature is 60-120℃ and the time is 2-12h; Optionally, the drying temperature can be any value between 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃ or 60-120℃, and the time can be any value between 2h, 4h, 6h, 8h, 10h, 12h or 2-12h. (3) The pre-firing temperature is 300-450℃ and the time is 1-4h; Optionally, the pre-firing temperature can be any value between 300℃, 350℃, 400℃, 450℃ or 300-450℃, and the time can be any value between 1h, 2h, 3h, 4h or 1-4h. (4) The inert atmosphere includes argon and / or nitrogen.

[0015] Preferably, the sintering includes: heating to 700-850°C at a heating rate of 1-5°C / min and holding at that temperature for 2-8 hours.

[0016] Optionally, the heating rate can be any value between 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min or 1-5℃ / min, and the holding temperature can be any value between 700℃, 750℃, 800℃, 850℃ or 700-850℃.

[0017] This application also provides a battery comprising the fast-ion conductor-carbon co-coated ternary cathode material.

[0018] Preferably, the battery is a solid-state battery.

[0019] This application also provides an electrical device, including the aforementioned battery.

[0020] Compared with the prior art, the beneficial effects of this application include: The fast-ion conductor-carbon co-coated ternary cathode material and its preparation method provided in this application have the following advantages: 1. "Ion-Electron" Dual Conductive Network to Solve the Kinetic Bottleneck: The LTP+carbon composite coating layer created in this invention provides a high-speed lithium-ion channel with LTP and in-situ generated carbon to construct an electronic conductive network. This solves the problems of slow ion transport and poor electron contact at the interface, avoids the decline in kinetic performance caused by traditional insulating coating layers, and significantly improves the rate performance and capacity utilization of the battery.

[0021] 2. Strong interfacial bonding, suppressing mechanical contact failure: Through the sol-gel method and subsequent heat treatment, the composite coating layer and the ternary matrix achieve a strong chemical bond, forming a strong and tough interface. This structure can better adapt to the volume changes of the active material during cycling, effectively preventing the coating layer from cracking or peeling due to stress, maintaining the long-term integrity and stability of the interface, thereby suppressing excessive local current and lithium dendrite growth caused by contact failure.

[0022] 3. The metal source used for in-situ synthesis of the coating layer will dop the transition metal sites of the ternary cathode material, effectively suppressing the irreversible phase transition during the cycling process of the cathode material.

[0023] 4. Excellent chemical stability and blocking of interfacial side reactions: The uniform and dense composite coating layer acts as a physical barrier, which can effectively isolate the direct contact between the ternary cathode and the sulfide electrolyte, fundamentally avoiding the aggravation of the space charge layer effect and the side reactions caused by reactive oxygen species, protecting the sulfide electrolyte and maintaining its high ionic conductivity.

[0024] 5. High versatility and wide protection scope: This invention can effectively coat and improve the performance of ternary materials with different nickel contents (Ni>0.5), covering a wide range of applications from medium nickel to high nickel, and has high technical versatility.

[0025] 6. Process Innovation: This invention utilizes in-situ carbonization of organic carbon sources under an inert atmosphere to simultaneously generate crystalline fast ion conductors and conductive carbon in a one-step process, which is simple and efficient. Compared with traditional coating technologies, it achieves superior performance without increasing process complexity. Detailed Implementation

[0026] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0027] Example 1 This embodiment provides a fast ion conductor-carbon co-coated ternary cathode material, specifically a LiTi2(PO4)3+ amorphous carbon composite coated NCM622 cathode material (Ni content 60%), with a coating amount of 3wt%.

[0028] The preparation method is as follows: 1. Formulation Calculation and Weighing: Based on coating 10g of NCM622, 0.3g of LTP is required. Calculations show the following required components: 0.053g lithium nitrate, 0.527g tetrabutyl titanate, and 0.267g ammonium dihydrogen phosphate. Citric acid is added at a 1:1 molar ratio to total metal ions (Li+Ti), amounting to 0.446g.

[0029] 2. Sol preparation: Dissolve lithium source, phosphorus source, and citric acid in 3.75 mL of deionized water. Dissolve titanium source in 11.25 mL of anhydrous ethanol. Under vigorous stirring, slowly add the ethanol solution dropwise to the aqueous solution, and continue stirring for 30 minutes to obtain a clear sol.

[0030] 3. Wet coating: Mix 10g of NCM622 with all the above sol and ball mill for 2 hours (300 rpm).

[0031] 4. Drying and pre-firing: Dry at 80℃ for 12 hours, then pre-firing in air at 350℃ for 2 hours.

[0032] 5. Inert atmosphere sintering: The pre-fired powder is placed in a tube furnace and heated to 775°C at 2°C / min under an argon atmosphere. The temperature is held for 6 hours and then cooled with the furnace to obtain the final product.

[0033] Comparative Example 1 Uncoated NCM622 cathode material.

[0034] Comparative Example 2 Except for step S4, which is carried out in an oxygen atmosphere, the other steps are exactly the same as in Example 1, resulting in carbon-free pure LTP coating.

[0035] Comparative Example 3 The traditional wet impregnation method was adopted, using aluminum isopropoxide as the aluminum source, to coat the surface of NCM622 with 3wt% Al2O3, and then sintering in air at 500℃ for 4 hours.

[0036] Comparative Example 4 NCM622 was dissolved in 15 mL of a water-ethanol mixture with an equal amount of citric acid (0.446 g) from the aforementioned formula. After drying and sintering at 775 °C under an argon atmosphere, NCM622 with only amorphous carbon coating was obtained.

[0037] The cathode materials obtained in each embodiment and the comparative example were assembled with Li6PS5Cl sulfide solid electrolyte to form solid-state mold batteries for testing. The test results are shown in Table 1 below: Table 1 Test Data

[0038] As shown in the table above, the composite coated cathode material prepared in Example 1 of this invention exhibits significantly superior overall performance compared to the comparative examples in terms of initial discharge capacity, first-cycle coulombic efficiency, rate performance, and long-cycle stability. Specifically, the performance improvement of Example 1 compared to Comparative Example 2 (pure LTP coating) lies in the introduction of amorphous carbon, which effectively improves the overall electronic conductivity of the coating layer, constructs a continuous electron transport path, and allows electron transport at the interface and ion transport via LTP to proceed in synergy, maintaining charge balance and thus significantly improving the initial capacity and discharge performance at high rates. The performance advantage of Example 1 compared to Comparative Example 4 (pure carbon coating) lies in the in-situ generated LiTi2(PO4)3 fast ion conductor having a three-dimensional ion diffusion channel, providing a rapid pathway for lithium ion migration between the core active material and the solid electrolyte. Although the carbon layer itself possesses good electronic conductivity and mechanical flexibility, its ability to block reactive oxygen species in the cathode is limited, making it difficult to effectively inhibit their continuous oxidative erosion of the sulfide electrolyte, resulting in a continuous increase in interfacial impedance with cycling. Therefore, the rate performance and long-term cycling stability of Comparative Example 4 are inferior to those of Example 1. The advantage of Example 1 over Comparative Example 3 (Al2O3 coating) lies in the fact that the LTP and amorphous carbon synergistic coating structure used in this invention successfully constructs an "ion-electron" dual continuous conductive network, which greatly reduces the interfacial impedance. In contrast, the Al2O3 coating layer used in Comparative Example 3 is essentially a dual insulator of ions and electrons, which introduces a significant charge transport barrier at the interface, leading to severe electrochemical polarization. Therefore, its initial capacity and rate performance are far inferior to those of Example 1.

[0039] Example 2 Using NCM811 cathode material (Ni content 80%), the remaining steps were exactly the same as in Example 1. The resulting material also exhibited excellent cycle stability (capacity retention of >83% after 100 cycles) and rate performance (1C / 0.1C >87%), proving the effectiveness of the present invention for high-nickel materials.

[0040] Example 3 The fast ion conductor type was changed to LiZr2(PO4)3, and the remaining steps were the same as in Example 1. The resulting material also exhibited electrochemical performance superior to that of conventional coated materials.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A ternary cathode material synergistically coated with a fast ion conductor-carbon, characterized in that, comprise a kernel and a composite coating layer; The inner core is a ternary positive electrode material, the chemical general formula of the ternary positive electrode material is LiNi x Mn y Co z O2, wherein x+y+z=1, and x>0.5, y>0, and z>0; the composite coating layer is composed of NASICON-type fast ionic conductor nanocrystals and amorphous carbon; the NASICON-type fast ionic conductor nanocrystals have a general chemical formula of LiM2(PO4)3, wherein M is one or more of Ti, Zr and Ge. 2.The ternary cathode material coated with fast-ion conductor-carbon synergistically according to claim 1, characterized in that, satisfy one or more of the following conditions: (1) the thickness of the composite coating layer is 5-20 nm, preferably 10-30 nm; (2) the composite coating layer accounts for 0.5%-10%, preferably 1%-5% of the total mass of the fast ionic conductor-carbon synergistically coated ternary positive electrode material; (3) the amorphous carbon accounts for 5%-40% of the total mass of the composite coating layer.

3. A method for preparing a ternary cathode material coated with a fast-ion conductor-carbon synergistically, according to claim 1 or 2, characterized in that, comprise: mixing a lithium source, an M source metal salt, a phosphorus source, an organic carbon source, water and anhydrous ethanol to obtain a precursor sol; mixing the ternary positive electrode material with the precursor sol and mechanically dispersing to obtain a slurry; drying the slurry to obtain a dry gel coated precursor, and then pre-burning in an air atmosphere and sintering in an inert atmosphere to obtain the fast ionic conductor-carbon synergistically coated ternary positive electrode material.

4. The preparation method of the fast-ion conductor-carbon synergistically coated ternary cathode material according to claim 3, characterized in that, satisfy one or more of the following conditions: (1) the lithium source comprises lithium nitrate and / or lithium acetate; (2) the M source metal salt comprises one or more of tetrabutyl titanate, tetraisopropyl titanate, zirconium oxychloride and tetraethyl germanate; (3) the phosphorus source comprises one or more of phosphoric acid, ammonium dihydrogen phosphate and diammonium hydrogen phosphate; (4) the organic carbon source comprises one or more of citric acid, oxalic acid, sucrose and polyvinylpyrrolidone, preferably citric acid.

5. The preparation method of the fast-ion conductor-carbon synergistically coated ternary cathode material according to claim 3, characterized in that, satisfy one or more of the following conditions: (1) the lithium source, the M source metal salt and the phosphorus source are measured according to the molar ratio of Li, M and P as (0.8-1.2):(1.8-2.2):(2.8-3.2); (2) the total molar amount ratio of the organic carbon source to metal ions is (0.8-1.5):1; (3) the volume ratio of the water to the anhydrous ethanol is 1:(2-4); (4) the volume of the precursor sol to the mass of the ternary positive electrode material is (0.5-2) mL / g.

6. The method for preparing the ternary cathode material coated with fast-ion conductor-carbon synergy according to claim 3, characterized in that, satisfy one or more of the following conditions: (1) the mechanical dispersion is ball milling or shear mixing, and the time is 0.5-3 h; (2) the drying temperature is 60-120℃, and the time is 2-12 h; (3) the pre-burning temperature is 300-450℃, and the time is 1-4 h; (4) the inert atmosphere comprises argon and / or nitrogen.

7. The method for preparing the ternary cathode material coated with fast-ion conductor-carbon synergistically according to any one of claims 3-6, characterized in that, the sintering comprises: increasing the temperature to 700-850℃ at a temperature increasing rate of 1-5℃ / min, and keeping the temperature for 2-8 h.

8. A battery, characterized by comprise the fast ionic conductor-carbon synergistically coated ternary positive electrode material of claim 1 or 2.

9. The battery of claim 8, wherein, the battery is a solid-state battery.

10. An electrical device, comprising: comprise the battery of claim 8 or 9.

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