Lithium-rich cation disordered rock salt positive electrode material as well as preparation method and application thereof

Abstract

The invention discloses a lithium-rich cation disordered rock salt positive electrode material as well as a preparation method and application thereof, and belongs to the technical field of preparation of lithium ion battery positive electrode materials. The method comprises the following steps: mixing a lithium source, a vanadium source and a titanium source according to a stoichiometric ratio of a general formula Li1 + xVyTizO2, carrying out ethanol wet grinding and drying, and pressing into a pure inorganic precursor green sheet under the condition of not adding a carbon source; clamping the precursor sheet between two carbon plates, initiating a reaction by using Joule heat conducted by the external carbon plates, executing multi-cycle short-time pulse heating, and realizing ultra-fast high-temperature sintering; and cooling the product, and performing ball-milling compounding on the cooled product and conductive carbon to obtain the target positive electrode material. The material prepared by the method is highly consistent with a product prepared by a traditional solid phase method in crystal structure, microstructure and electrochemical performance, and is an efficient and low-energy-consumption alternative scheme with great industrialization prospects.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode material preparation technology, and particularly relates to a lithium-rich cation disordered rock salt cathode material, its preparation method and application. Background Technology

[0002] Cation-Disordered Rocksalt (DRX) cathode materials are widely recognized as core potential materials for next-generation high-energy-density lithium-ion batteries due to their high theoretical specific capacity and the ability to utilize elements such as vanadium and titanium. However, the current mainstream traditional high-temperature solid-state method has significant technical drawbacks: this method requires high-temperature calcination for more than 10 hours to ensure sufficient atomic diffusion, which not only consumes a lot of energy but also results in low production efficiency; in addition, during the long-term high-temperature treatment and slow cooling process, lithium volatilization easily occurs on the material surface, and it reacts with H2O and CO2 in the air to generate residual lithium (mainly Li2CO3 and LiOH), resulting in poor air stability of the material, which in turn severely restricts its processing performance.

[0003] In recent years, Joule heating technology with rapid heating rates has been gradually introduced into this field in an attempt to solve the aforementioned problems. However, existing Joule heating processes still have significant limitations: most require the carbon source (such as acetylene black) to be mixed into the precursor to achieve conductivity, a typical example being the scheme of directly mixing acetylene black with the cathode precursor powder and then performing Joule heating sintering. This method of internally mixing the carbon source not only increases the complexity of precursor preparation, but also, because carbon is a strong reducing agent at high temperatures, the inertness requirements of the reaction atmosphere are extremely stringent. If not properly controlled, it may lead to abnormal valence states of transition metals, affecting material properties.

[0004] Therefore, developing a new process that can maintain the high performance of solid-state products while significantly reducing atmosphere sensitivity and improving preparation efficiency has become an urgent need in this field. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a lithium-rich cation disordered rock salt cathode material, its preparation method, and its applications. This invention employs an external carbon plate heating mode, abandoning the traditional design of premixed carbon sources within the precursor, significantly reducing the stringent requirements for the sintering atmosphere. Simultaneously, leveraging the ultra-fast reaction characteristics of pulsed Joule heating technology, the preparation cycle is compressed to a fraction of the time required by traditional processes, successfully constructing an efficient and low-cost alternative to the traditional solid-state method, and the resulting product exhibits excellent air stability.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A lithium-rich cation-disordered rock salt cathode material with the general chemical formula Li 1+x Vy Ti z O2(LVTO), where 0.1≤x≤0.3, 0.3≤y≤0.7, and 0.2≤z≤0.5.

[0008] The material provided by this invention belongs to the lithium-rich cation disordered rock salt system, inheriting the core advantage of high theoretical specific capacity of this system, and can make resource-based use of common elements such as vanadium and titanium, providing core potential materials for the next generation of high energy density lithium-ion batteries; the element ratio range in the general formula is precisely matched to the requirements of atomic diffusion and phase formation, ensuring the stability of the material's crystal structure and the consistency of its electrochemical performance.

[0009] Furthermore, the chemical formula of the lithium-rich cation disordered rock salt cathode material includes: Li 1.2 V 0.4 Ti 0.40 O2, Li 1.17 V 0.50 Ti 0.33 O2 or Li 1.13 V 0.60 Ti 0.26 O2.

[0010] This invention specifies three concrete compositions, making the material composition more precise and controllable, which facilitates quality control in industrial production. The materials with these concrete compositions have been experimentally verified to have a crystal structure in the Fm-3m space group, exhibiting excellent electrochemical performance (such as high discharge specific capacity and a gentle cycle decay trend) and outstanding air stability.

[0011] This invention also provides a method for preparing a lithium-rich cation disordered rock salt cathode material, comprising the following steps:

[0012] According to the general chemical formula Li 1+x V y Ti z Lithium source, vanadium source and titanium source were weighed in stoichiometric proportions for O2, and anhydrous ethanol was added for wet grinding. After natural air drying to remove the anhydrous ethanol, the resulting mixed powder was pressed into shape, and a green precursor sheet was obtained without adding any carbon source and conductive agent.

[0013] The green precursor sheet is sandwiched between two carbon plates and subjected to Joule heating sintering under a protective atmosphere (current is applied to the carbon plates under a protective atmosphere, and the Joule heat generated by the carbon plates is used to initiate the precursor reaction through heat conduction, and a multi-cycle short-time pulse heating program is executed to achieve ultra-fast high-temperature sintering); after the reaction is completed, heating is stopped and the material is cooled to room temperature; the sintered product is mixed with conductive carbon material and ball-milled to obtain the lithium-rich cation disordered rock salt cathode material.

[0014] This invention abandons the "internal carbon source" design of traditional Joule heating process and adopts external carbon plate heat transfer, simplifying the precursor preparation process and reducing the inertness requirements of the sintering atmosphere (no need for an extremely high-purity atmosphere), thus improving process tolerance and industrial feasibility. Multi-cycle short-time pulse Joule heating sintering achieves ultra-fast preparation, compressing the preparation cycle of more than 10 hours in the traditional solid-state method to a few hundredths, significantly reducing energy consumption and improving production efficiency. The product is highly consistent with the product of the traditional solid-state method in terms of crystal structure, microstructure and electrochemical performance, and the "fast burning and fast cooling" reduces the formation of residual lithium on the surface, resulting in significantly better air stability than the product of the traditional process.

[0015] Furthermore, the lithium source is selected from at least one of lithium carbonate (Li2CO3), lithium hydroxide, lithium oxide, and lithium nitrate; to eliminate the impact of lithium loss during heating, an excess of 3% of the lithium source is weighed.

[0016] Furthermore, the vanadium source is selected from at least one of vanadium pentoxide, vanadium trioxide (V2O3), vanadium dioxide, and ammonium metavanadate.

[0017] Furthermore, the titanium source is selected from at least one of titanium dioxide (TiO2) and titanium hydroxide.

[0018] The lithium source (lithium carbonate, etc.), vanadium source (vanadium pentoxide, etc.), and titanium source (titanium dioxide, etc.) specified in this invention are all conventional raw materials that are readily available in the market, widely sourced, and cost-controllable, facilitating industrial mass production. The raw materials have stable chemical properties and are suitable for processes such as wet grinding and high-temperature sintering, ensuring the uniformity of precursor mixing and guaranteeing the sufficiency of subsequent reactions and the stability of product performance.

[0019] Furthermore, the pressing pressure is 5-20 MPa; the thickness of the green precursor sheet is 0.5-2.0 mm.

[0020] The pressure limit allows the precursor powder to form a dense and uniform green body structure, which is conducive to the efficient conduction of Joule heat and avoids insufficient local sintering. Reasonable green body morphology parameters ensure uniform atomic diffusion paths during sintering, improve the crystallinity and microstructure consistency of the product, and reduce unreacted precursor residues.

[0021] Furthermore, the carbon plate is a high-purity graphite plate or a graphene composite plate.

[0022] High-purity graphite plates or graphene composite plates have excellent electrical and thermal conductivity, enabling them to quickly generate and conduct Joule heat, ensuring the stability and controllability of ultra-fast sintering reactions. The external carbon plate does not directly contact the precursor, avoiding abnormal transition metal valence states that may be caused by internal carbon source mixing, thus ensuring the stability of the material's electrochemical performance from the source.

[0023] Furthermore, the specific operation steps of the Joule heating sintering are as follows: under an argon atmosphere, the sintering temperature is controlled at 900-1100℃, the single heating duration is 10-60 seconds, and the number of cyclic heating cycles is 2-5 times.

[0024] This parameter combination provides the transient high-temperature energy required for atomic diffusion while avoiding lithium volatilization and surface side reactions caused by prolonged high temperatures. The ultra-rapid heating and cooling characteristics significantly shorten the residence time of the material in the sensitive temperature range of 200-500℃ for residual lithium formation, significantly reduce the generation of surface impurities, and improve the air stability of the material. The multi-cycle short-time pulse mode ensures sufficient sintering, avoids insufficient crystallinity caused by short single heating time, and ensures that the product forms a pure Fm-3m space group rock salt phase structure.

[0025] Furthermore, the specific operating steps of the Joule heating sintering are as follows: under an argon atmosphere, the sintering temperature is controlled at 950°C, the single heating duration is 20 seconds, and the number of heating cycles is 3. The cumulative residence time of the green precursor sheet at a sintering temperature above 900°C does not exceed 300 seconds.

[0026] Furthermore, the conductive carbon material is selected from at least one of acetylene black, Ketjen black, superconducting carbon black, carbon nanotubes, and graphene; acetylene black is preferred.

[0027] Acetylene black, Ketjen black, and other conductive carbon materials have excellent electrical conductivity and can build a continuous conductive network inside the material, which significantly improves the electronic conduction efficiency of the target material and improves the charge-discharge kinetics performance.

[0028] Furthermore, the amount of the conductive carbon material added is 5-20 wt% of the mass of the sintered product, preferably 10 wt%.

[0029] Limiting the amount of conductive carbon material added allows for a precise balance between conductivity and intrinsic capacity, avoiding both poor conductivity due to insufficient addition and excessive addition that could reduce the volume of active material and decrease specific capacity.

[0030] Furthermore, the specific operation steps of the ball milling process are as follows: the sintered product is mixed with conductive carbon material and ball milled in a ball mill at a speed of 200-500 rpm for 2-10 hours.

[0031] The limitation of these ball milling parameters enables uniform composite formation of conductive carbon materials and sintered products, refining particle size and improving material dispersibility. The uniform composite effect and suitable particle size can optimize the contact area between the material and the electrolyte, reduce interfacial impedance, and further improve the charge-discharge efficiency and cycle stability of the battery.

[0032] Furthermore, the specific steps of the ball milling process are as follows: the sintered product is mixed with conductive carbon material and ball milled in a ball mill at a speed of 500 rpm for 5-10 hours.

[0033] The lithium-rich cation disordered rock salt cathode material prepared by the method of the present invention has an Fm-3m space group structure. After being exposed to an air environment at a temperature of 25°C and a relative humidity of 50% for 72 hours, its initial discharge capacity retention rate is not less than 80%.

[0034] This invention also provides an application of lithium-rich cation disordered rock salt cathode material in lithium-ion batteries.

[0035] This material combines high theoretical specific capacity, good cycle stability, and excellent air stability, which can significantly improve the energy density and lifespan of lithium-ion batteries. It is compatible with the industrial production process of lithium-ion batteries, providing high-performance cathode material solutions for lithium-ion batteries in high-energy demand scenarios (such as new energy vehicles and energy storage equipment), and promoting the industrial application of next-generation high-energy-density lithium-ion batteries.

[0036] This invention achieves precise control over the material structure and surface chemical state by combining a specific carbon-source-free precursor design with an external Joule heating process. The specific principle is as follows:

[0037] (1) Principle of Improved Atmosphere Tolerance and Simplified Process: This invention abandons the heating mode of "internal carbon source mixing" in traditional Joule heating technology, and adopts a scheme in which the precursor itself does not contain a carbon source and heat is transferred using an external carbon plate. Since there is no highly reducing carbon powder inside the precursor, the sensitivity of the carbothermic reduction reaction at high temperature to atmospheric fluctuations is eliminated. This design allows the sintering process to be carried out stably in an inert atmosphere with a purity of not less than 99.9%, without pursuing extreme purity, reducing the requirements for equipment airtightness and atmosphere purity, and eliminating the process of premixing carbon in the precursor, thus improving the simplicity and universality of the process.

[0038] (2) Principle of high air stability: Due to the slow cooling of traditional solid-state methods, the material remains in the 200-500℃ temperature range for a long time, which is the sensitive area for the formation of residual lithium (Li2CO3 / LiOH) on the surface. This invention utilizes the ultra-fast heating and cooling characteristics of Joule heating technology (>50℃ / s) to greatly reduce the residence time of the material in the sensitive temperature range for residual lithium formation. This "fast heating and fast cooling" process effectively locks in the clean surface structure at high temperature, significantly reduces the formation of non-electrochemically active surface impurities, and endows the material with excellent moisture resistance and air stability from the root.

[0039] (3) High-efficiency substitution and phase formation principle: This invention utilizes the transient high-temperature energy provided by Joule heating, which greatly improves the reaction kinetics. Experiments have shown that only about 1 minute of effective heating time is needed to drive lithium, vanadium, and titanium atoms to complete the diffusion and rearrangement across the potential barrier, constructing an Fm-3m rock salt phase structure that is completely consistent with the 10-hour solid-state method. In terms of microstructure, the pulsed high temperature is sufficient to induce normal nucleation and densification of grains, avoiding insufficient crystallinity caused by short time. This invention achieves "replacing hourly time with minute-level time", and the product performance is highly consistent with the solid-state method, possessing the potential to completely replace traditional high-energy-consuming processes.

[0040] Compared with the prior art, the present invention has the following advantages and technical effects:

[0041] (1) High preparation efficiency and low energy consumption: This invention shortens the preparation cycle by nearly 600 times and the prepared material is comparable to the solid-state method product in terms of crystal structure, microstructure and electrochemical performance, thus achieving high-efficiency preparation;

[0042] (2) Excellent air stability: Thanks to the ultrafast preparation process, the material surface is clean and its moisture resistance is significantly better than that of traditional solid-phase products;

[0043] (3) High process tolerance: The design without internal mixing carbon source reduces the sensitivity to sintering atmosphere, simplifies the pretreatment process, and is easy to control in industrial applications.

[0044] (4) High consistency of performance: The prepared materials are highly consistent with the solid-state product in terms of crystal structure, microstructure and electrochemical performance, and the performance is not sacrificed due to rapid preparation. Attached Figure Description

[0045] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0046] Figure 1 The XRD patterns of the cathode materials prepared in Example 1 and Comparative Example 1 are shown below.

[0047] Figure 2 SEM images of the cathode materials prepared in Example 1 and Comparative Example 1;

[0048] Figure 3 Batteries prepared using the cathode materials in Examples 1-3 and Comparative Examples 1-3 were tested at room temperature at 10 mA·g. -1 Comparison of the first three charge-discharge curves under current density;

[0049] Figure 4 A comparison of the capacity retention rates of batteries prepared with the cathode materials in Examples 1-3 and Comparative Examples 1-3 during long-term cycling.

[0050] Figure 5 The results are obtained by reassembling batteries after the cathode materials prepared in Example 1 and Comparative Example 1 were directly exposed to air for 3 days. Detailed Implementation

[0051] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0052] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0053] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0054] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This specification and embodiments are merely exemplary.

[0055] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0056] This invention provides a preparation step for a lithium-rich cation-disordered rock salt cathode material:

[0057] I. Basic Information of Materials

[0058] The lithium-rich cation-disordered rock salt cathode material prepared by this invention has the general chemical formula Li. 1+x V y Ti zO2 (LVTO), wherein the molar ratios of each element satisfy 0.1≤x≤0.3, 0.3≤y≤0.7, and 0.2≤z≤0.5; the preferred chemical formula is Li. 1.2 V 0.40 Ti 0.40 O2, Li 1.17 V 0.50 Ti 0.33 O2 or Li 1.13 V 0.60 Ti 0.26 O2.

[0059] II. Experimental Preparation Steps

[0060] (I) Precursor Preparation

[0061] 1. Raw material selection and weighing: According to the general chemical formula of the target material, Li 1+x V y Ti z To determine the stoichiometric ratio of O2, weigh out the lithium source, vanadium source, and titanium source. The lithium source is selected from at least one of lithium carbonate, lithium hydroxide, lithium oxide, and lithium nitrate (for example, lithium carbonate is selected). To eliminate the impact of lithium loss during heating, the lithium source should be weighed in excess by 3%. The vanadium source is selected from at least one of vanadium pentoxide, vanadium trioxide, vanadium dioxide, and ammonium metavanadate (for example, vanadium trioxide is selected). The titanium source is selected from at least one of titanium dioxide and titanium hydroxide (for example, titanium dioxide is selected).

[0062] 2. Mixing and drying: Add the weighed lithium source, vanadium source and titanium source to anhydrous ethanol, wet grind until uniformly mixed, and then air dry to remove anhydrous ethanol.

[0063] 3. Compression molding: Without adding any carbon source or conductive agent, the dried mixed powder is placed in a mold and compressed under a pressure of 5-20 MPa (exemplary, the pressure is set to 6 MPa) to obtain a green precursor sheet with a thickness of 0.5-2.0 mm.

[0064] (ii) Joule heating reaction

[0065] 1. Clamping and Atmosphere Control: The green precursor sheet is clamped between two high-purity graphite plates or graphene composite plates, and the whole assembly is placed in an argon protective atmosphere.

[0066] 2. Joule heating sintering: An electric current is applied to the carbon plate holding the green sheet, and the Joule heat generated by the carbon plate is used to initiate the precursor reaction through heat conduction. A multi-cycle, short-time pulse heating program is executed to achieve ultra-fast high-temperature sintering. The heating program is controlled as follows: sintering temperature 900-1100℃, single heating duration 10-60 seconds, and 2-5 cycles of heating; the preferred parameters are sintering temperature 950℃, single heating duration 20 seconds, 3 cycles of heating, and the cumulative residence time of the green precursor sheet at a sintering temperature above 900℃ does not exceed 300 seconds.

[0067] 3. Cooling: After the reaction is complete, stop heating and allow the sintered product to cool naturally to room temperature along with the carbon plate.

[0068] (III) Ball milling composite treatment

[0069] 1. Material mixing: The sintered product cooled to room temperature is mixed with a conductive carbon material, wherein the conductive carbon material is selected from at least one of acetylene black, Ketjen black, superconducting carbon black, carbon nanotubes and graphene (preferably acetylene black), and its addition amount is 5-20 wt% (preferably 10 wt%) of the mass of the sintered product.

[0070] 2. Ball milling: Place the mixed material into a ball mill and mill at a speed of 200-500 rpm for 2-10 hours; preferably at a speed of 500 rpm for 5-10 hours (e.g., 5 hours). After ball milling, the target lithium-rich cation disordered rock salt cathode material is obtained.

[0071] Unless otherwise specified, "room temperature" in this invention refers to 25±2℃.

[0072] All raw materials used in this invention were purchased from the market.

[0073] The technical solution of the present invention will be further illustrated by the following embodiments.

[0074] Example 1

[0075] A lithium-rich cation disordered rock salt cathode material (Li 1.2 V 0.40 Ti 0.40 The preparation of O2 is as follows:

[0076] (1) Preparation of green precursor sheets: according to the chemical formula Li 1.2 V 0.40 Ti 0.40 To determine the stoichiometric ratio of O2, weigh Li2CO3, V2O3, and TiO2, add anhydrous ethanol, and wet grind until uniformly mixed. Then, air dry to remove the anhydrous ethanol. Take 0.4g of the dried mixed powder and place it in a mold. Press it into a green precursor sheet with a diameter of 13mm and a thickness of 1.75mm under a pressure of 6MPa.

[0077] (2) Joule heating sintering: The green precursor sheet prepared in step (1) is sandwiched between two high-purity graphite plates and the whole is placed in an argon protective atmosphere. Current is applied to the carbon plate holding the green sheet, and the Joule heat generated by the carbon plate is used to initiate the precursor reaction through heat conduction. A multi-cycle short-time pulse heating program is executed to achieve ultra-fast high-temperature sintering. The heating program is controlled as follows: sintering temperature 950℃, single heating duration 20 seconds, 3 cycles of heating to achieve ultra-fast high-temperature sintering. After the reaction is completed, heating is stopped and the sintered product is allowed to cool naturally to room temperature with the carbon plate.

[0078] (3) Ball milling composite treatment: The sintered product cooled to room temperature in step (2) is mixed with acetylene black, and the amount of acetylene black added is 10 wt% of the mass of the sintered product; the mixed material is put into a ball mill and ball milled at 300 rpm for 5 hours to obtain the target lithium-rich cation disordered rock salt cathode material.

[0079] Example 2

[0080] A lithium-rich cation disordered rock salt cathode material (Li 1.17 V 0.50 Ti 0.33 The preparation of O2 is as follows:

[0081] (1) Preparation of green precursor sheets: according to the chemical formula Li 1.17 V 0.50 Ti 0.33 To determine the stoichiometric ratio of O2, weigh Li2CO3, V2O3, and TiO2, add anhydrous ethanol, and wet grind until uniformly mixed. Then, air dry to remove the anhydrous ethanol. Take 0.4g of the dried mixed powder and place it in a mold. Press it into a green precursor sheet with a diameter of 13mm and a thickness of 1.75mm under a pressure of 6MPa.

[0082] (2) Joule heating sintering: The green precursor sheet prepared in step (1) is sandwiched between two high-purity graphite plates and the whole is placed in an argon protective atmosphere. Current is applied to the carbon plate holding the green sheet, and the Joule heat generated by the carbon plate is used to initiate the precursor reaction through heat conduction. A multi-cycle short-time pulse heating program is executed to achieve ultra-fast high-temperature sintering. The heating program is controlled as follows: sintering temperature 950℃, single heating duration 20 seconds, 3 cycles of heating to achieve ultra-fast high-temperature sintering. After the reaction is completed, heating is stopped and the sintered product is allowed to cool naturally to room temperature with the carbon plate.

[0083] (3) Ball milling composite treatment: The sintered product cooled to room temperature in step (2) is mixed with acetylene black, and the amount of acetylene black added is 10 wt% of the mass of the sintered product; the mixed material is put into a ball mill and ball milled at 300 rpm for 5 hours to obtain the target lithium-rich cation disordered rock salt cathode material.

[0084] Example 3

[0085] A lithium-rich cation disordered rock salt cathode material (Li 1.13 V 0.60 Ti 0.26 The preparation of O2 is as follows:

[0086] (1) Preparation of green precursor sheets: according to the chemical formula Li 1.13 V 0.60 Ti 0.26 To determine the stoichiometric ratio of O2, weigh Li2CO3, V2O3, and TiO2, add anhydrous ethanol, and wet grind until uniformly mixed. Then, air dry to remove the anhydrous ethanol. Take 0.4g of the dried mixed powder and place it in a mold. Press it into a green precursor sheet with a diameter of 13mm and a thickness of 1.75mm under a pressure of 6MPa.

[0087] (2) Joule heating sintering: The green precursor sheet prepared in step (1) is sandwiched between two high-purity graphite plates and the whole is placed in an argon protective atmosphere. Current is applied to the carbon plate holding the green sheet, and the Joule heat generated by the carbon plate is used to initiate the precursor reaction through heat conduction. A multi-cycle short-time pulse heating program is executed to achieve ultra-fast high-temperature sintering. The heating program is controlled as follows: sintering temperature 950℃, single heating duration 20 seconds, 3 cycles of heating to achieve ultra-fast high-temperature sintering. After the reaction is completed, heating is stopped and the sintered product is allowed to cool naturally to room temperature with the carbon plate.

[0088] (3) Ball milling composite treatment: The sintered product cooled to room temperature in step (2) is mixed with acetylene black, and the amount of acetylene black added is 10 wt% of the mass of the sintered product; the mixed material is put into a ball mill and ball milled at 300 rpm for 5 hours to obtain the target lithium-rich cation disordered rock salt cathode material.

[0089] Comparative Example 1

[0090] A method for preparing Li using a traditional solid-state method 1.2 V 0.40 Ti 0.40 The steps for using O2 are as follows:

[0091] (1) Preparation of green precursor sheets: Same as in Example 1;

[0092] (2) High-temperature solid-state sintering: The green precursor sheet prepared in step (1) is placed in an alumina crucible and placed in a tube furnace. The temperature is raised to 950°C at 5°C / min under an argon atmosphere and held for 10 hours. Then it is naturally cooled to room temperature with the furnace (cooling takes about 5-8 hours).

[0093] (3) Ball milling composite treatment: The sintered product cooled to room temperature in step (2) is mixed with acetylene black, and the amount of acetylene black added is 10 wt% of the mass of the sintered product; the mixed material is put into a ball mill and ball milled at 300 rpm for 5 hours to obtain the cathode material.

[0094] Comparative Example 2

[0095] A method for preparing Li using a traditional solid-state method 1.17 V 0.50 Ti 0.33 The steps for using O2 are as follows:

[0096] (1) Preparation of green precursor sheets: Same as in Example 2;

[0097] (2) High-temperature solid-state sintering: The green precursor sheet prepared in step (1) is placed in an alumina crucible and placed in a tube furnace. The temperature is raised to 950°C at 5°C / min under an argon atmosphere and held for 10 hours. Then it is naturally cooled to room temperature with the furnace (cooling takes about 5-8 hours).

[0098] (3) Ball milling composite treatment: The sintered product cooled to room temperature in step (2) is mixed with acetylene black, and the amount of acetylene black added is 10 wt% of the mass of the sintered product; the mixed material is put into a ball mill and ball milled at 300 rpm for 5 hours to obtain the cathode material.

[0099] Comparative Example 3

[0100] A method for preparing Li using a traditional solid-state method 1.13 V 0.60 Ti 0.26 The steps for using O2 are as follows:

[0101] (1) Preparation of green precursor sheets: Same as in Example 3;

[0102] (2) High-temperature solid-state sintering: The green precursor sheet prepared in step (1) is placed in an alumina crucible and placed in a tube furnace. The temperature is raised to 950°C at 5°C / min under an argon atmosphere and held for 10 hours. Then it is naturally cooled to room temperature with the furnace (cooling takes about 5-8 hours).

[0103] (3) Ball milling composite treatment: The sintered product cooled to room temperature in step (2) is mixed with acetylene black, and the amount of acetylene black added is 10 wt% of the mass of the sintered product; the mixed material is put into a ball mill and ball milled at 300 rpm for 5 hours to obtain the cathode material.

[0104] Figure 1 The images show the XRD patterns of the cathode materials prepared in Example 1 and Comparative Example 1. Figure 1 It can be observed that although the effective heating time of Example 1 is only 1 minute, its diffraction peaks highly overlap with those of Comparative Example 1, and both match well with the standard cation disordered rock salt structure of the Fm-3m space group, with no obvious impurity peaks appearing.

[0105] Figure 2 SEM images of the cathode materials prepared in Example 1 and Comparative Example 1 are shown. Figure 2 As shown, the morphology of the sample in Example 1 was not significantly different from that in Comparative Example 1. Both samples consisted of well-sintered particles with dense surfaces and no obvious unreacted precursor residues. This indicates that shortening the preparation time did not affect the evolution of the material's microstructure. The transient high temperature provided by Joule heating was sufficient to support normal grain growth and densification, thus ensuring that the material had a compaction density and structural stability comparable to solid-state products.

[0106] Performance testing:

[0107] The materials prepared in Examples 1-3 and Comparative Examples 1-3 were used as positive electrode materials to fabricate coin cells, and their electrochemical performance was tested. The fabrication method of the coin cells is as follows:

[0108] The obtained positive electrode material was thoroughly mixed with polyvinylidene fluoride (PVDF) and conductive carbon (AB) at a mass ratio of 70:15:15. Then, 80 μL of N-methylpyrrolidone (NMP) was added dropwise to form a uniform slurry. The slurry was uniformly coated onto aluminum foil using a 100 μm doctor blade. The coated electrode sheet was dried in a vacuum oven at 70 °C to remove solvent components. The drying time was 12 h. After drying, the electrode sheet was cut to obtain the positive electrode sheet. The electrolyte was a LiPF6 solution with a concentration of 1 mol / L, wherein the solvent was diethylene glycol dimethyl ether solution. The lithium metal sheet was used as the counter electrode, and a polypropylene membrane was used as the separator.

[0109] In an argon-atmospheric glove box (water and oxygen content both <0.1ppm), CR2032 coin cells were assembled in the following order: positive electrode shell - positive electrode sheet - Celgard 2500 separator - lithium metal sheet - gasket - spring sheet - negative electrode shell. The assembled coin cells were then allowed to age statically before being tested for electrochemical performance on a Newway CT-4008Tn battery tester. The test voltage range was set to 1.5V-4.8V, and the test was conducted at room temperature at 10mA·g.-1 Constant current charge-discharge tests were performed using the current density, and the results showed that:

[0110] Figure 3 Batteries prepared using the cathode materials in Examples 1-3 and Comparative Examples 1-3 were tested at room temperature at 10 mA·g. -1 A comparison of the first three charge-discharge curves at different current densities. From Figure 3 It can be clearly observed that the charge-discharge curves of the samples in Examples 1-3 and the corresponding comparative examples 1-3 highly overlap. Both exhibit almost identical open-circuit voltage, charge-discharge voltage plateau, and specific capacity. The discharge specific capacity of Example 1 and Comparative Example 1 is around 120 mAh / g, and the voltage hysteresis is basically the same. Examples 2 and 3, compared to Comparative Examples 2 and 3, show higher discharge specific capacities than Examples 1 and Comparative Example 1 due to the increased vanadium content in the active material and the increased number of electrons participating in the redox reaction. The charge-discharge curves of Examples 2 and 3 are also highly similar to those of Comparative Examples 2 and 3. This high degree of similarity strongly proves that the Joule heating process of this invention shortens the high-temperature reaction time from 10 hours to about 1 minute while providing sufficient energy to drive the lithium, vanadium, and titanium atoms to complete sufficient diffusion and rearrangement. A lithium-rich cation disordered rock salt crystal structure and redox active sites are constructed that are completely consistent with the traditional long-time solid-state method. The Joule heating method does not sacrifice the intrinsic capacity of the material due to rapid preparation.

[0111] Figure 4 This is a comparison chart showing the capacity retention of batteries prepared using the cathode materials in Examples 1-3 and Comparative Examples 1-3 during long-cycle operation. Figure 4 It can be clearly observed that after 30 charge-discharge cycles, the capacity retention of the samples in Examples 1-3 is very close to that of the samples in Comparative Examples 1-3. The capacity decay trend of Examples 1-3 is gradual, without a sudden drop, indicating that the lattice structure formed under ultrafast thermal shock has good mechanical stability and electrochemical reversibility. Particularly noteworthy is that, due to the extremely short preparation time of the Joule heating method, the material surface is less susceptible to erosion by moisture in the air, and interfacial side reactions are suppressed. Therefore, in certain cycling stages, the coulombic efficiency and capacity retention of the sample examples show a trend superior to those of the comparative examples. The consistency of cycling performance further confirms that the material prepared by this invention has excellent structural stability.

[0112] Figure 5 The results are from the battery reassembly test after the cathode materials prepared in Example 1 and Comparative Example 1 were directly exposed to air for 3 days (72 hours at 25°C and 50% humidity). Figure 5It can be clearly observed that the initial capacity and capacity retention of Example 1 are both superior to those of Comparative Example 1, and remain stable in subsequent cycles. This is attributed to the extremely short high-temperature exposure time of the Joule heating method, which effectively suppresses the side reactions between the surface lithium source and moisture in the air, resulting in a cleaner and more stable material surface.

[0113] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A lithium-rich cation-disordered rock salt cathode material, characterized in that, Its general chemical formula is Li 1+x V y Ti z O2, where 0.1≤x≤0.3, 0.3≤y≤0.7, and 0.2≤z≤0.

5.

2. The lithium-rich cation disordered rock salt cathode material according to claim 1, characterized in that, The chemical formula of the lithium-rich cation-disordered rock salt cathode material includes: Li 1.2 V 0.40 Ti 0.40 O2, Li 1.17 V 0.50 Ti 0.33 O2 or Li 1.13 V 0.60 Ti 0.26 O2.

3. A method for preparing a lithium-rich cation-disordered rock salt cathode material as described in claim 1 or 2, characterized in that, Includes the following steps: Lithium source, vanadium source and titanium source were weighed according to the stoichiometric ratio of the general chemical formula, and anhydrous ethanol was added for wet grinding. After natural air drying to remove the anhydrous ethanol, the resulting mixed powder was pressed into shape to obtain a green precursor sheet. The green precursor sheet is sandwiched between two carbon plates and sintered by Joule heating under a protective atmosphere. After the reaction is completed, heating is stopped and the material is cooled to room temperature. The sintered product is mixed with conductive carbon material and ball-milled to obtain the lithium-rich cation disordered rock salt cathode material.

4. The preparation method according to claim 3, characterized in that, The lithium source is selected from at least one of lithium carbonate, lithium hydroxide, lithium oxide, and lithium nitrate; The vanadium source is selected from at least one of vanadium pentoxide, vanadium trioxide, vanadium dioxide, and ammonium metavanadate; The titanium source is selected from at least one of titanium dioxide and titanium hydroxide.

5. The preparation method according to claim 3, characterized in that, The pressing pressure is 5-20 MPa; the thickness of the green precursor sheet is 0.5-2.0 mm.

6. The preparation method according to claim 3, characterized in that, The carbon plate is a high-purity graphite plate or a graphene composite plate.

7. The preparation method according to claim 3, characterized in that, The specific operation steps of the Joule heating sintering are as follows: under an argon atmosphere, the sintering temperature is controlled at 900-1100℃, the single heating duration is 10-60 seconds, and the number of heating cycles is 2-5.

8. The preparation method according to claim 3, characterized in that, The conductive carbon material is selected from at least one of acetylene black, Ketjen black, superconducting carbon black, carbon nanotubes, and graphene. The amount of conductive carbon material added is 5-20 wt% of the mass of the sintered product.

9. The preparation method according to claim 3, characterized in that, The specific steps of the ball milling process are as follows: the sintered product is mixed with conductive carbon material and ball milled in a ball mill at a speed of 200-500 rpm for 2-10 hours.

10. The application of a lithium-rich cation disordered rock salt cathode material as described in claim 1 or 2 in a lithium-ion battery.

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