A high-power lithium-rich manganese-based positive electrode material and a preparation method and application thereof

Abstract

This invention provides a high-power lithium-rich manganese-based cathode material, its preparation method, and its application, belonging to the technical field of lithium-ion battery cathode materials. The invention involves mixing and stirring lithium-rich manganese-based powder with polyallylamine hydrochloride, allowing the polyallylamine hydrochloride to positively charge the surface of the lithium-rich manganese-based material particles, followed by the addition of Ti3C2T. x The dispersion was stirred and mixed to bring the surface of the positively charged lithium-rich manganese-based material particles into contact with Ti3C2T. x The high-power lithium-rich manganese-based cathode material is obtained by directional electrostatic adsorption of functional groups on the surface of nanosheets, followed by liquid nitrogen freeze-thaw treatment and freeze-drying. The process of this invention is simple and controllable, with high raw material utilization, avoiding complex high-temperature secondary treatments or chemical modification steps, and is easy to scale up for industrial production, showing promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode material technology, and particularly relates to a high-power lithium-rich manganese-based cathode material, its preparation method and application. Background Technology

[0002] Lithium-ion batteries, as a highly efficient energy storage device, have been widely used in electric vehicles, portable electronic devices, and large-scale energy storage power stations due to their advantages such as high energy density, long cycle life, and environmental friendliness. With the development of electric vehicles towards longer range and faster charging, and the stringent requirements for energy density and power performance in special batteries and electric aircraft, existing lithium-ion battery cathode materials are no longer sufficient to meet practical application needs. Developing cathode materials with high energy density, high power performance, and low cost has become a core trend in the industry.

[0003] The chemical formula of the lithium-rich manganese-based cathode material can be represented as xLi₂MnO₃•(1-x)LiMnO₂ (M = transition metal elements such as Ni, Co, and Mn). It is a nanoscale composite solid solution formed by Li₂MnO₃ and layered LiMO₂. Based on a unique oxygen anion redox reaction mechanism, its theoretical specific capacity can exceed 300 mAh g⁻¹. -1 It far exceeds the current mainstream ternary materials (200-220 mAh g). -1 ) and lithium iron phosphate materials (160-170 mAh g) -1 This material is expected to directly increase the energy density of power batteries by more than 50%. At the same time, it boasts significant advantages such as abundant manganese resources, low cost, and environmental friendliness, and is regarded by the industry as a "holy grail" technology route to break through the energy density ceiling, representing one of the important development directions for next-generation lithium-ion battery cathode materials.

[0004] However, in practical applications, especially under high-power conditions, lithium-rich manganese-based cathode materials still suffer from a series of intrinsic defects, which seriously restrict their industrialization and widespread application. The core issues are concentrated in the following aspects: First, the cycle voltage continuously decays. During the charge and discharge cycle, the migration and dissolution of transition metal ions will induce the irreversible evolution of the material's crystal structure from layered to spinel phase or even disordered rock salt structure, resulting in a continuous decline in the working voltage platform, which in turn causes the battery energy density to decay rapidly. Second, the rate performance is insufficient. The material has low intrinsic electronic conductivity and slow lithium-ion solid-phase diffusion rate, resulting in significant kinetic shortcomings. Under high current charge and discharge (high power conditions), the specific capacity decreases sharply, making it difficult to meet the requirements of fast charging and high power applications of power batteries. Third, during charge-discharge cycles, the material undergoes irreversible release of lattice oxygen, which is accompanied by side reactions at the electrolyte interface that consume active lithium, resulting in a large amount of irreversible loss of active lithium and significantly reducing the usable capacity of the battery.

[0005] Previous studies have attempted to use MXene materials for coating and modifying lithium-rich manganese-based cathode materials, for example, by using surfactants such as CTAB (hexadecyltrimethylammonium bromide) to achieve MXene coating through electrostatic adsorption. However, such methods still have the following shortcomings: CTAB is a small molecule surfactant, and its ability to modify the charge on the particle surface is limited, making it difficult to achieve a uniform and stable distribution of MXene nanosheets on the particle surface; at the same time, during conventional drying, MXene sheets are prone to recombination, resulting in a significant reduction in specific surface area and active sites, weakening the conductive network construction effect. To address these issues, this invention proposes a high-power lithium-rich manganese-based cathode material, its preparation method, and its applications. Summary of the Invention

[0006] To address the problems of poor electronic conductivity, insufficient rate performance, and structural instability during cycling in existing lithium-rich manganese-based cathode materials, this invention proposes a high-power lithium-rich manganese-based cathode material, its preparation method, and its applications. This invention features a simple and highly controllable process. It utilizes polyallylamine hydrochloride (PAH) to bond few-layer or monolayer Ti3C2T... x The material is uniformly coated in lithium-rich manganese-based cathode material to construct a protective layer with high conductivity, high ion transport, and stable material structure, thereby preparing lithium-rich manganese-based cathode material with high power and long cycle life.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a high-power lithium-rich manganese-based cathode material, comprising the following steps: Lithium-rich manganese-based powder was mixed and stirred with polyallylamine hydrochloride to positively charge the surface of the lithium-rich manganese-based material particles. Then Ti3C2T was added. x The dispersion was stirred and mixed to bring the surface of the positively charged lithium-rich manganese-based material particles into contact with Ti3C2T. x Functional groups on the surface of nanosheets undergo directional electrostatic adsorption to obtain a mixed solution; The mixed solution was subjected to liquid nitrogen freeze-thaw treatment and freeze-drying treatment in sequence to obtain the high-power lithium-rich manganese-based cathode material.

[0008] Liquid nitrogen freezing combined with freeze-drying technology is mainly used in existing technologies to maintain the microstructure of materials. However, in this invention, it is mainly used to solve the stacking problem of MXene coating layers and to achieve uniform coating of two-dimensional materials by controlling the polyelectrolyte interface. Specifically, in the preparation method of the high-power lithium-rich manganese-based cathode material of this invention, liquid nitrogen freezing can achieve "ultra-rapid freezing," inhibiting excessive ice crystal growth and preventing phase separation. This can instantly freeze ions and Ti3C2T in the solution. x The nanosheets are "locked in situ" in their originally uniformly dispersed state, avoiding macroscopic aggregation and phase separation. If conventional freezing is used instead, the mechanical action of ice crystal expansion easily compresses adjacent MXene sheets together, leading to severe stacking and significantly reducing active sites and ion transport channels. However, the tiny ice crystals formed by rapid liquid nitrogen freezing in this invention act like "support pillars" to expand the sheets, making it easier to obtain fewer or thinner layers of Ti3C2T after freeze-drying. x Encapsulation structure.

[0009] The core of this invention for preparing high-power lithium-rich manganese-based cathode materials lies in introducing polyallylamine hydrochloride as a cationic polyelectrolyte to positively charge the surface of lithium-rich manganese-based powder, thereby achieving efficient coupling and stable assembly between the lithium-rich manganese-based material and two-dimensional MXene nanosheets. Specifically, polyallylamine hydrochloride can dissociate into a large number of protonated amino groups (-NH3) in aqueous solution. + Cationic polymers of ). Wherein: (1) Protonated amino group (-NH3) + ) and deprotonated hydroxyl groups (-O) on the surface of lithium-rich manganese-based materials - Ion pair electrostatic adsorption occurs, forming a cation "coating layer" on the surface of the lithium-rich manganese-based material, completing the charge reversal from negative to positive charge; (2) The positively charged surface is further used as a "bridging site" to connect with the two-dimensional Ti3C2T x -O on the surface of nanosheets - Functional groups such as -F form stable ion pairs, achieving directional adsorption and interfacial anchoring, while also avoiding the stacking of MXene itself, greatly improving composite uniformity and interfacial binding force. (3) Polyallylamine hydrochloride, as a polymeric electrolyte, can improve the dispersibility of lithium-rich manganese-based powder in water and effectively prevent particle agglomeration. This is particularly useful in subsequent two-dimensional Ti3C2T... x Uniform coating of nanosheets provides better preconditions; Polyallylamine hydrochloride not only acts as a dispersant, but also plays a crucial role in the "interface construction and regulation core" of the system, enabling the realization of two-dimensional Ti3C2T by combining liquid nitrogen freeze-thaw method. xThe uniform coating and stable bonding of nanosheets to the surface of lithium-rich manganese-based particles significantly enhances the overall electrochemical performance of the material based on the aforementioned multiple synergistic effects. Compared with existing technologies using small molecule surfactants such as CTAB, the polyallylamine hydrochloride used in this invention is a high-molecular-weight polyelectrolyte that can form a more stable and uniform charge-modified layer on the particle surface, providing more MXene anchoring sites. Simultaneously, this invention innovatively introduces a liquid nitrogen freeze-thaw method, solving the industry-wide common problem of MXene sheets easily stacking during the drying process, achieving a dual guarantee of chemically directed adsorption and physical freeze-locking.

[0010] (4) In this invention, the interfacial electrical regulation of polyallylamine hydrochloride and the liquid nitrogen freeze-thaw treatment are not simply superimposed processes, but rather exhibit a significant synergistic effect. Specifically, PAH first constructs a uniform and stable cationic polyelectrolyte layer on the surface of lithium-rich manganese-based particles. This layer not only acts as a "charge reversal layer" and an "anchoring bridging layer" to guide Ti3C2T X The directional adsorption of nanosheets, through the steric hindrance effect of long polymer chains, pre-suppresses the spontaneous aggregation of MXene sheets in the liquid phase. Based on this, ultra-rapid freezing with liquid nitrogen instantly "freezes and locks" the uniformly dispersed PAH-MXene-particle composite system, preventing the MXene sheets from being compressed and stacked, and the PAH molecular chains from re-entanglement due to the slow growth of ice crystals during subsequent drying. Simultaneously, the mechanical stress of the micro-ice crystals generated by repeated freeze-thaw cycles further disperses residual weak MXene aggregates and promotes the full expansion and redistribution of PAH molecular chains on the particle surface. This synergistic strategy of "chemically directed adsorption + physical freeze-locking" cannot be achieved by using PAH alone (which easily stacks during drying without freeze-locking) or by using liquid nitrogen freeze-thaw alone (which results in disordered adsorption without uniform charge modification), demonstrating the core innovation of this invention that distinguishes it from existing technologies.

[0011] Furthermore, the liquid nitrogen freeze-thaw treatment includes: freezing the mixed solution with liquid nitrogen and then thawing it, followed by continuing to freeze it with liquid nitrogen. The liquid nitrogen freeze-thaw treatment process is repeated at least 3 times. The liquid nitrogen freezing is freezing the mixed solution with liquid nitrogen and placing it at a temperature of -20°C for 24 hours. The thawing is transferring the frozen mixed solution to room temperature to thaw it.

[0012] Taking three liquid nitrogen freeze-thaw cycles as an example, the process is as follows: the mixed solution is immersed in liquid nitrogen to freeze, causing the solution temperature to drop rapidly to -196°C for ultra-rapid freezing. Then, it is transferred to a -20°C freezer for one day. The frozen mixture is then transferred to room temperature to thaw. After thawing, it is further frozen with liquid nitrogen and placed in a -20°C freezer for one day. After that, the frozen mixture is transferred to room temperature to thaw. After thawing, it is further frozen with liquid nitrogen and placed in a -20°C freezer for one day. After that, the frozen mixture is transferred to room temperature to thaw again. After thawing, it is further frozen with liquid nitrogen and placed in a -20°C freezer for one day.

[0013] Furthermore, the mass ratio of the lithium-rich manganese-based powder to polyallylamine hydrochloride is 20:1.

[0014] Furthermore, the Ti3C2T x The amount of dispersion added makes Ti3C2T x The mass percentage of the high-power lithium-rich manganese-based cathode material is 1%.

[0015] Furthermore, the Ti3C2T x The dispersion was obtained by etching the Al layer in the MAX phase precursor Ti3AlC2 and then ultrasonically exfoliating it.

[0016] The Ti3C2T described in this invention x Ti3C2T in dispersion x few-layer or single-layer Ti3C2T x Few-layer or single-layer Ti3C2T x As a highly conductive structural framework, it can significantly improve the overall electron transport capability of the electrode and effectively suppress the structural degradation of lithium-rich manganese-based materials during cycling.

[0017] Furthermore, the lithium-rich manganese-based powder is a layered oxide synthesized by a high-temperature solid-state method. The precursor is a nickel-cobalt-manganese oxide coprecipitation precursor. The preparation method is as follows: the nickel-cobalt-manganese oxide coprecipitation precursor is dried and pretreated, then mixed and ground with lithium carbonate. The resulting mixture is sintered at 850°C for 12 hours in air atmosphere. After sintering, it is naturally cooled in the furnace to obtain the lithium-rich manganese-based powder.

[0018] This invention also provides a high-power lithium-rich manganese-based cathode material, prepared by the above method. The cathode material comprises lithium-rich manganese-based active material particles and Ti3C2T coated on the surface and between the active material particles. x The Ti3C2T x The interfacial electrochemical properties induced by polyallylamine hydrochloride are uniformly distributed on the surface of the active material particles and bind to the active material particles.

[0019] The present invention also provides an application of the high-power lithium-rich manganese-based cathode material described above in lithium-ion batteries.

[0020] The high-power lithium-rich manganese-based cathode material of this invention is cut to a diameter of 1.4 cm and has a mass in the range of 3.3 mg to 3.8 mg. Its operating voltage is 2-4.8 V, and after 500 cycles at 1C, its capacity remains at 229.5 mAh g. -1 It exhibits high chemical stability at low current densities.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects: (1) This invention realizes two-dimensional Ti3C2T by interfacial electrical regulation and structural construction induced by polyallylamine hydrochloride and uniform coating by liquid nitrogen freeze-thaw method. x The uniform distribution and stable bonding of nanosheets on the surface of lithium-rich manganese-based particles endow them with advantages such as high conductivity, high capacity and high stability, effectively improving the rate performance and stability of lithium ions, thus obtaining a highly stable lithium-ion cathode material with a long cycle life.

[0022] (2) The high-power lithium-rich manganese-based cathode material of the present invention is prepared by a combination of chemical coating, liquid nitrogen freeze-thaw and freeze-drying. The process is simple and controllable, the raw material utilization rate is high, and the complex high-temperature secondary treatment or chemical modification steps are avoided. It is easy to realize industrial scale-up production and has good application prospects. Attached Figure Description

[0023] 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: Figure 1 This is a schematic diagram of the preparation process of the high-power lithium-rich manganese-based cathode material in an embodiment of the present invention; Figure 2 SEM images of the high-power lithium-rich manganese-based cathode material prepared in Example 1 at different magnifications; Figure 3 This is a comparison chart of the rate performance of the cathode materials of Example 1 and Comparative Examples 1-3 at different rates; Figure 4 This is a comparison chart of the long-cycle performance of the cathode materials in Example 1, Comparative Examples 1 and 3 at 1C rate; Figure 5 The DC charge-discharge (GCD) curves of the cathode material in Example 1 at different numbers of cycles at 1C rate are shown. Figure 6 The results are the electrochemical impedance spectroscopy (EIS) test results of the cathode materials in Example 1, Comparative Examples 1 and 3. Detailed Implementation

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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 apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0028] 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.

[0029] This invention provides a method for preparing a high-power lithium-rich manganese-based cathode material, comprising the following steps: Lithium-rich manganese-based powder was mixed and stirred with polyallylamine hydrochloride (PAH) to positively charge the surface of the lithium-rich manganese-based material particles. Then, Ti3C2T was added. x The dispersion was stirred and mixed to bring the surface of the positively charged lithium-rich manganese-based material particles into contact with Ti3C2T. x Functional groups on the surface of nanosheets undergo directional electrostatic adsorption to obtain a mixed solution; The mixed solution was subjected to liquid nitrogen freeze-thaw treatment and freeze-drying treatment in sequence to obtain a high-power lithium-rich manganese-based cathode material.

[0030] In a preferred embodiment of the present invention, the liquid nitrogen freeze-thaw treatment includes: freezing the mixed solution with liquid nitrogen and then thawing it, followed by further freezing with liquid nitrogen. The liquid nitrogen freeze-thaw treatment process is repeated at least three times. Liquid nitrogen freezing involves freezing the mixed solution with liquid nitrogen and placing it at -20°C for 24 hours, while thawing involves transferring the frozen mixture to room temperature to thaw. Taking three liquid nitrogen freeze-thaw treatments as an example, specifically: immersing the mixed solution in liquid nitrogen to freeze it, rapidly lowering the solution temperature to -196°C for ultra-rapid freezing, then transferring it to a -20°C freezer for one day, transferring the frozen mixture to room temperature to thaw, and after thawing, further freezing with liquid nitrogen and placing it at -20°C for one day, then transferring the frozen mixture to room temperature to thaw, and after thawing, further freezing with liquid nitrogen and placing it at -20°C for one day, then transferring the frozen mixture to room temperature to thaw again, and after thawing, further freezing with liquid nitrogen and placing it at -20°C for one day.

[0031] In a preferred embodiment of the present invention, the mass ratio of lithium-rich manganese-based powder to polyallylamine hydrochloride is 20:1.

[0032] In a preferred embodiment of the present invention, Ti3C2T x The amount of dispersion added makes Ti3C2T x The mass percentage of high-power lithium-rich manganese-based cathode materials is 1%.

[0033] In a preferred embodiment of the present invention, Ti3C2T x The dispersion was obtained by etching the Al layer in the MAX phase precursor Ti3AlC2 and then ultrasonically exfoliating it; the specific preparation method was as follows: HF was generated in situ using LiF and dilute hydrochloric acid to etch the MAX phase Ti3AlC2, and after etching for 24 hours, multilayer Ti3C2T was obtained. x The dispersion solution will be used to etch the multilayer Ti3C2T x The dispersion was centrifuged with an appropriate amount of deionized water, and then ultrasonically treated for 4 hours to obtain few-layer or monolayer Ti3C2T. x Dispersion.

[0034] In a preferred embodiment of the present invention, the lithium-rich manganese-based powder is a layered oxide synthesized by a high-temperature solid-state method. The precursor is a nickel-cobalt-manganese oxide co-precipitation precursor. The preparation method is as follows: the nickel-cobalt-manganese carbonate precursor is pretreated by drying in a vacuum oven at 105°C for 12 hours. 1 g of the dried precursor and 0.433 g of lithium carbonate are weighed and thoroughly ground and mixed in a mortar. The mixture is placed in a muffle furnace and sintered at 850°C for 12 hours in an air atmosphere. After sintering, the mixture is naturally cooled with the furnace to obtain the lithium-rich manganese-based powder.

[0035] This invention also provides a high-power lithium-rich manganese-based cathode material, prepared by the above method. The cathode material includes lithium-rich manganese-based active material particles and Ti3C2T coated on the surface and between the active material particles. x Ti3C2T x The interfacial electrochemical properties induced by polyallylamine hydrochloride are uniformly distributed on the surface of active material particles and bind to the active material particles.

[0036] The high-power lithium-rich manganese-based cathode material prepared in the embodiments of the present invention can be used to prepare lithium-ion batteries.

[0037] All raw materials used in the embodiments of this invention were purchased commercially.

[0038] A schematic diagram of the preparation process of the high-power lithium-rich manganese-based cathode material in this invention is shown in the embodiment of the invention. Figure 1 .

[0039] The technical solution of the present invention will be further illustrated by the following embodiments.

[0040] Example 1 (1) The nickel cobalt manganese carbonate precursor was pretreated by drying in a vacuum oven at 105°C for 12 hours. 1 g of the dried precursor and 0.433 g of lithium carbonate were weighed and thoroughly ground and mixed in a mortar. The mixture was placed in a muffle furnace and sintered at 850°C for 12 hours in air atmosphere. After sintering, the mixture was naturally cooled with the furnace to obtain lithium-rich manganese-based powder (lithium-rich manganese-based active material). (2) The MAX phase Ti3AlC2 was generated in situ by LiF and dilute hydrochloric acid and etched with HF. After etching for 24 hours, a multilayer Ti3C2T was obtained. x The dispersion solution will be used to etch the multilayer Ti3C2T x The dispersion was centrifuged with deionized water, and then subjected to ultrasonic treatment for 4 hours to obtain few-layer or monolayer Ti3C2T. x Dispersion; (3) Place 0.2g of lithium-rich manganese-based powder and 0.01g of polyallylamine hydrochloride in a beaker, add 20mL of deionized water to the beaker, and stir in a magnetic stirrer for 1h to allow the protonated ammonium ions (-NH4+) in the polyallylamine hydrochloride molecules to form protonated ammonium ions (-NH4+). 3+ Ti3C2T preferentially adsorbs onto the particle surface, completing the surface electrical regulation and organic interface layer construction; after stirring, 0.2 mL of monolayer or few-layer Ti3C2T is then introduced. x The dispersion (concentration of 10 mg / mL, this amount added makes Ti3C2T) xThe mass percentage of the final product cathode material is 1%. Then, deionized water is added to the mixture to make the total volume 40 mL, and then the mixture is stirred evenly for 2 hours (because the surface of the lithium-rich manganese-based material is already positively charged at this time, it can undergo directional electrostatic adsorption with the negatively charged functional groups on the surface of the two-dimensional material, thereby achieving uniform coating). (4) Subsequently, the stirred mixture was added to a centrifuge tube and centrifuged at 5000 rpm for 5 minutes 3 times. Then, the mixture was transferred to a freezer at -20°C for 1 day. After freezing, the mixture was transferred to room temperature to thaw. After thawing, it was further frozen with liquid nitrogen and placed in a freezer for 1 day. The liquid nitrogen freeze-thaw process was repeated 3 times. Finally, the centrifuge tube frozen with liquid nitrogen was transferred to a freeze dryer to freeze dry and obtain two-dimensional Ti3C2T. x High-power lithium-rich manganese-based cathode material coated (denoted as LRM / Ti3C2T) x (1% chemical), where "chemical" refers to the chemical coating modification method, and 1% refers to Ti3C2T x (mass percentage in the final cathode material).

[0041] Figure 2 The images shown are SEM images of the high-power lithium-rich manganese-based cathode material prepared in Example 1 at different magnifications. It can be seen that the cathode material exhibits spherical particles with obvious two-dimensional Ti3C2T particles on the surface. x Coating layer.

[0042] Comparative Example 1 The nickel-cobalt-manganese carbonate precursor was pretreated by drying in a vacuum oven at 105°C for 12 hours. 1 g of the dried precursor and 0.433 g of lithium carbonate were weighed and thoroughly ground and mixed in a mortar. The mixture was placed in a muffle furnace and sintered at 850°C for 12 hours in air atmosphere. After sintering, the mixture was naturally cooled with the furnace to obtain lithium-rich manganese-based powder (denoted as LRM).

[0043] Comparative Example 2 (1)-(2) Lithium-rich manganese-based powder / few-layer or monolayer Ti3C2T x The preparation method of the dispersion is the same as in Example 1; (3) Place 0.2g of lithium-rich manganese-based powder and 0.01g of polyallylamine hydrochloride in a beaker, add 20mL of deionized water to the beaker, and stir in a magnetic stirrer for 1h to allow the protonated ammonium ions (-NH4+) in the polyallylamine hydrochloride molecules to form protonated ammonium ions (-NH4+). 3+ Ti3C2T preferentially adsorbs onto the particle surface, completing surface electrical regulation and organic interface layer construction; after stirring, 2 mL of monolayer or few-layer Ti3C2T is then introduced. x The dispersion (concentration of 10 mg / mL, this amount added makes Ti3C2T) xThe mass percentage of the final product cathode material is 10%. Then, deionized water is added to the mixture to make the total volume 40 mL, and then the mixture is stirred evenly for 2 hours (because the surface of the lithium-rich manganese-based material is already positively charged at this time, it can undergo directional electrostatic adsorption with the negatively charged functional groups on the surface of the two-dimensional material, thereby achieving uniform coating). (4) Subsequently, the stirred mixture was added to a centrifuge tube and centrifuged at 5000 rpm for 5 minutes 3 times. Then, the mixture was transferred to a freezer at -20°C for 1 day. After freezing, the mixture was transferred to room temperature to thaw. After thawing, it was further frozen with liquid nitrogen and placed in a freezer for 1 day. The liquid nitrogen freeze-thaw process was repeated 3 times. Finally, the centrifuge tube frozen with liquid nitrogen was transferred to a freeze dryer for freeze drying to obtain lithium-rich manganese-based cathode material (denoted as LRM / Ti3C2T). x (10% conversion).

[0044] Comparative Example 3 (1)-(2) Lithium-rich manganese-based powder / few-layer or monolayer Ti3C2T x The preparation method of the dispersion is the same as in Example 1; (3) Place 0.2g of lithium-rich manganese-based powder in a beaker, add 15mL of deionized water to the beaker and stir until homogeneous. After stirring, introduce 0.2mL of monolayer or few-layer Ti3C2T. x The dispersion (concentration of 10 mg / mL, this amount added makes Ti3C2T) x The mass percentage of the final product cathode material is 1%. Then, deionized water is added to the mixture to make the total volume 40 mL, and then the mixture is stirred evenly for 2 hours. (4) Subsequently, the stirred mixture was added to a centrifuge tube and centrifuged at 5000 rpm for 5 minutes 3 times. Then, the mixture was transferred to a freezer at -20°C for 1 day. After freezing, the mixture was transferred to room temperature to thaw. After thawing, it was further frozen with liquid nitrogen and placed in a freezer for 1 day. The liquid nitrogen freeze-thaw process was repeated 3 times. Finally, the centrifuge tube frozen with liquid nitrogen was transferred to a freeze dryer to freeze dry, and the positive electrode material (denoted as LRM / Ti3C2T) was obtained. x (1% material), where "material" refers to the physical mixing method.

[0045] Performance testing The positive electrode materials obtained in Example 1 and Comparative Examples 1-3 were mixed with conductive carbon black and binder (PVDF concentration of 0.035 g / mL, specifically obtained by uniformly mixing and dissolving PVDF powder with N-methylpyrrolidone solution) in a mass ratio of 8:1:1 to form a slurry. The slurry was uniformly coated on aluminum foil and vacuum dried in a vacuum drying oven at 105°C for 12 hours to obtain an electrode sheet.

[0046] The electrode sheets prepared above are used to assemble lithium-ion half-cells through processes such as rolling and weighing. The electrolyte is KLD-LP75 lithium-ion battery electrolyte (containing 1.0M LiPF6 and 0.2M LiDFOB, with a solvent FEC:EMC:DFEA volume ratio of 1:2:1).

[0047] The prepared lithium-ion battery cathode was tested, with rate performance tests conducted at 1C, 2C, 5C, 10C, 20C, and 50C, then returning to 1C. Long-cycle performance was tested at 1C rate.

[0048] Figure 3 The graph shows a comparison of the rate performance of the cathode materials in Example 1 and Comparative Examples 1-3 at different rate capacities. It can be seen that after 5 cycles at different rate capacities of 1C, 2C, 5C, 10C, 20C, and 50C, the LRM / Ti3C2T cathode material in Example 1 exhibits the following performance: x The capacities of (1% chemically modified) surface-coated materials can reach 244 mAh g. -1 230 mAh g -1 201 mAh g -1 173mAh g -1 143 mAh g -1 and 105 mAh g -1 It significantly outperforms uncoated pure LRM material and other control group materials, exhibiting excellent high-power characteristics. Furthermore, after the rate capability returns to 1C, the LRM / Ti3C2T ratio... x (1% chemical coating) The surface-modified material exhibits relatively stable reversibility. This is because in Example 1, chemical bonding was achieved through PAH induction, followed by spherical uniform bonding via liquid nitrogen freeze-thaw method, resulting in a uniform and stable distribution of a two-dimensional Ti3C2T layer on the surface of the lithium-rich manganese-based material. x Nanosheets were used to construct a highly conductive physicochemical protective layer on the surface of lithium-rich manganese-based material particles.

[0049] The rate performance of Comparative Example 2 (10% Ti) was significantly lower than that of Example 1 (1% Ti), because Comparative Example 2 had 10% Ti3C2T added by mass. x The nanosheets far exceed the critical value required to form a "monolayer or few-layer uniform coating," thus accumulating on the particle surface to form a dense and continuous thick shell. The path for lithium ions to cross this thick shell from the electrolyte into the internal active material becomes significantly longer, and the solid-phase diffusion resistance increases sharply. At the same time, the addition of 10% by mass also far exceeds the anchoring points provided by PAH. Excess MXene that is not effectively anchored is prone to leaching and stacking in the interparticle spaces, forming local "dead zones." This not only reduces conductivity but may also clog macropores, hindering sufficient electrolyte wetting and increasing contact resistance.

[0050] Figure 4 The graph shows a comparison of the long-cycle performance of the cathode materials in Example 1, Comparative Examples 1 and 3 at a 1C rate. It can be seen that LRM / Ti3C2T x The (1% chemically modified) surface-coated material exhibited a stable capacity of approximately 230 mAh g⁻¹ after 500 cycles at 1C rate. -1 The performance fluctuated slightly. After 500 cycles, the capacity was 229.5 mAh g. -1 Compared to pure LRM (153.2 mAh g), -1 ) and without the use of cationic polyelectrolyte LRM / Ti3C2T x (1% substance) (197.7 mAh g -1 Its cycle stability is superior. This is because the uniform and stable two-dimensional Ti3C2T in Example 1... x Nanosheet coating can serve as a protective layer, effectively mitigating the erosion of active materials by the electrolyte, reducing interfacial side reactions, and inhibiting irreversible structural phase transitions of materials during cycling, thereby significantly improving capacity retention at 1C rate.

[0051] Figure 5 The above are the DC charge-discharge (GCD) curves of the cathode material in Example 1 at different numbers of cycles at a 1C rate. It can be seen that the two-dimensional Ti3C2T in Example 1... x The chemically surface-coated modified lithium-rich manganese-based cathode material exhibits good chemical stability after 500 cycles at 1C rate, with the GCD remaining essentially unchanged.

[0052] Figure 6 The electrochemical impedance spectroscopy (EIS) results of the cathode materials in Example 1, Comparative Example 1, and Comparative Example 3 show that LRM / Ti3C2T x The charge transfer impedance of the (1% chemically coated) surface-modified material is significantly reduced compared to the pure LRM material, indicating that the two-dimensional Ti3C2T x The introduction of nanosheets successfully constructed a highly efficient conductive network, accelerating electron and ion transport.

[0053] 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.

Claims

1. A method for preparing a high-power lithium-rich manganese-based cathode material, characterized in that, Includes the following steps: Lithium-rich manganese-based powder was mixed and stirred with polyallylamine hydrochloride to positively charge the surface of the lithium-rich manganese-based material particles. Then Ti3C2T was added. x The dispersion was stirred and mixed to bring the surface of the positively charged lithium-rich manganese-based material particles into contact with Ti3C2T. x Functional groups on the surface of nanosheets undergo directional electrostatic adsorption to obtain a mixed solution; The mixed solution was subjected to liquid nitrogen freeze-thaw treatment and freeze-drying treatment in sequence to obtain the high-power lithium-rich manganese-based cathode material.

2. The method for preparing the high-power lithium-rich manganese-based cathode material according to claim 1, characterized in that, The liquid nitrogen freeze-thaw process includes: freezing the mixed solution with liquid nitrogen and then thawing it, followed by continuing to freeze it with liquid nitrogen, and repeating the liquid nitrogen freeze-thaw process at least 3 times.

3. The method for preparing the high-power lithium-rich manganese-based cathode material according to claim 2, characterized in that, The liquid nitrogen freezing process involves freezing the mixed solution with liquid nitrogen and placing it at -20°C for 24 hours. The thawing process involves transferring the frozen mixed solution to room temperature for thawing.

4. The method for preparing the high-power lithium-rich manganese-based cathode material according to claim 1, characterized in that, The mass ratio of the lithium-rich manganese-based powder to polyallylamine hydrochloride is 20:

1.

5. The method for preparing the high-power lithium-rich manganese-based cathode material according to claim 1, characterized in that, The Ti3C2T x The amount of dispersion added makes Ti3C2T x The mass percentage of the high-power lithium-rich manganese-based cathode material is 1%.

6. The method for preparing the high-power lithium-rich manganese-based cathode material according to claim 1, characterized in that, The Ti3C2T x The dispersion was obtained by etching the Al layer in the MAX phase precursor Ti3AlC2 and then ultrasonically exfoliating it.

7. The method for preparing the high-power lithium-rich manganese-based cathode material according to claim 1, characterized in that, The lithium-rich manganese-based powder is a layered oxide synthesized by a high-temperature solid-state method, and the precursor is a nickel-cobalt-manganese oxide co-precipitation precursor.

8. The method for preparing the high-power lithium-rich manganese-based cathode material according to claim 7, characterized in that, The method for preparing the lithium-rich manganese-based powder is as follows: the nickel-cobalt-manganese oxide co-precipitation precursor is dried and pretreated, then mixed and ground with lithium carbonate, and the resulting mixture is sintered at 850°C for 12 hours in air atmosphere. After sintering, it is naturally cooled in the furnace to obtain the lithium-rich manganese-based powder.

9. A high-power lithium-rich manganese-based cathode material, characterized in that, The cathode material is prepared by the method described in any one of claims 1-8, wherein the cathode material comprises lithium-rich manganese-based active material particles and Ti3C2T coated on the surface and between the active material particles. x The Ti3C2T x The interfacial electrochemical properties induced by polyallylamine hydrochloride are uniformly distributed on the surface of the active material particles and bind to the active material particles.

10. The application of the high-power lithium-rich manganese-based cathode material as described in claim 9 in lithium-ion batteries.

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