A pre-oxidized lithium-rich manganese-based substrate cathode material, its preparation method and application

Abstract

This invention discloses a pre-oxidized lithium-rich manganese-based layered cathode material, its preparation method, and its applications, relating to the field of lithium-ion battery cathode material technology. The lithium-rich manganese-based layered cathode material of this invention is a lithium-based oxide cathode composed of multiple transition metal elements. A pre-oxidized transition metal precursor material was obtained through a modified open co-precipitation strategy, which, combined with subsequent lithiation sintering, yielded a series of lithium-rich layered oxides with different degrees of pre-oxidation. Compared to lithium-rich layered oxides obtained by traditional co-precipitation followed by sintering, the pre-oxidized lithium-rich cathode exhibits significantly improved output energy density and cycle performance, and the open-system design facilitates industrial production.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, and in particular to a pre-oxidized lithium-rich manganese-based basal cathode material, its preparation method, and its application. Background Technology

[0002] In recent years, with the country's strategic deployment of new energy systems and high requirements for energy density, the demand for high-performance lithium batteries in industries such as energy storage systems and emerging portable devices has gradually increased. In terms of lithium-ion battery structure, the cathode material, as the direct source of lithium ions, directly determines the energy storage capacity of the lithium-ion battery through its discharge specific capacity and other performance characteristics. However, the representative cathode materials that have already been commercialized, such as lithium cobalt oxide, lithium iron phosphate, and layered nickel-cobalt-manganese ternary cathodes, have discharge specific capacities that are approaching their usable limits and still cannot meet the stringent requirements currently placed on lithium-ion batteries. Therefore, seeking and developing new cathode material systems has become a common challenge for both industry and academia.

[0003] It is worth noting that lithium-rich manganese-based cathode materials (xLiMO2·(1-x)Li2MnO3), due to their unique two-phase structure, exhibit a unique charge compensation mechanism that combines cation and lattice oxygen-related anionic redox reactions. They are considered the most promising cathode materials for lithium-ion batteries, potentially overcoming range anxiety in industries such as electric vehicles. However, the deep delithiation behavior corresponding to the high specific capacity during charging inevitably brings many problems. For example, the presence of lithium vacancies in the transition metal layer lowers the migration barrier of transition metal ions, causing irreversible interlayer and intralayer migration of the transition metal in the delithiated lithium-rich cathode. This further triggers oxygen dimerization, ultimately leading to irreversible oxygen release and the formation of harmful oxygen holes. Meanwhile, the high charging voltage required for oxygen behavior activation exacerbates the challenges of the electrode / electrolyte interface, which will face harmful electrolyte decomposition reactions and further erode the electrode surface, ultimately leading to severe structural collapse and phase transitions. Therefore, lithium-rich manganese-based substrate oxides face problems such as severe irreversible capacity loss in the first cycle, poor cycle performance, and severe voltage decay, which seriously restrict their industrialization.

[0004] Currently, scientists are using methods such as bulk element doping, surface doping, and surface coating to mitigate the activity of lattice oxygen redox reactions and increase the binding energy between transition metals and oxygen, thereby suppressing severe oxygen dimerization and improving the reversibility of oxygen redox reactions. While this can partially alleviate the irreversible behavior of lithium-rich cathodes, these methods come at the cost of capacity, which is not conducive to fully utilizing the performance advantages of lithium-rich cathodes. In summary, current design strategies cannot simultaneously achieve the high energy density and high stability of lithium-rich manganese-based lattice oxides, making it difficult to achieve a milestone breakthrough in performance. Summary of the Invention

[0005] To address the aforementioned shortcomings, the main objective of this invention is to provide a lithium-rich manganese-based substrate cathode material based on pre-oxidation design, which, when applied to lithium-ion batteries, exhibits excellent output energy density, cycle performance, and rate performance during charge and discharge processes, thereby meeting the application and development requirements of related fields.

[0006] The present invention also provides a method for preparing lithium-rich manganese-based morphological cathode material and its application. The method is based on an open pre-oxidation co-precipitation reaction, combined with a subsequent high-temperature calcination strategy to prepare the above-mentioned lithium-rich manganese-based morphological cathode. The process is simple, can achieve large-scale mass production, and has low cost. When used as a cathode material in lithium-ion batteries, it can significantly improve their cycle and structural stability.

[0007] To address the problems in the existing technology, the technical solution adopted by this invention is as follows: A lithium-rich manganese-based substrate cathode material based on pre-oxidation, comprising a lithium-based multi-element oxide derived from a transition metal precursor obtained through a pre-oxidation reaction, wherein the main transition metal element is a mixture of at least two of Ni, Co, and Mn.

[0008] Preferably, the aforementioned lithium-rich manganese-based substrate cathode material based on pre-oxidation further includes one or more of the following doping elements: B, Na, Mg, Al, P, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Sb, Zr, Nb, Mo, or W.

[0009] The above-mentioned method for preparing lithium-rich manganese-based substrate cathode materials based on pre-oxidation design includes the following steps: Step 1: Mix at least two transition metal ion sources with water to obtain a transition metal mixed solution A; Step 2: Mix the alkali source with water to prepare alkali solution B; and prepare complexing agent C; Step 3: Add an ammonia solution as the reaction base liquid to a co-precipitation reactor with an adjustable atmosphere. Step 4: The transition metal mixed solution A, alkaline solution B and complexing agent C are simultaneously pumped into the above coprecipitation reactor, heated and stirred to form a dynamic high-temperature reaction system; Step 5: Control the pH of the reaction system to ensure a uniform and orderly coprecipitation reaction and nucleation growth process; Step 6: After feeding is completed, age for several hours, place the obtained material in a container for solid-liquid separation, centrifugal washing, and high-temperature drying to obtain pre-oxidized transition metal precursor D; Step 7: Mix the pre-oxidized transition metal precursor D and lithium source E uniformly according to the molar ratio to obtain the reaction precursor; Step 8: Place the reaction precursor in a high-temperature furnace and calcine it at high temperature for several hours under a set atmosphere to obtain the lithium-rich manganese-based substrate cathode material based on pre-oxidation design.

[0010] Preferably, the alkaline solution B mentioned in step 2 is one or more of sodium carbonate or sodium hydroxide; the complexing agent C is ammonia.

[0011] Preferably, the reactor environment in step 3 is a completely open system or a gas flow controllable environment; the atmosphere is an air atmosphere; if it is a gas flow controllable environment, the air flow rate m ranges from 0 to 1. <m<50 L / h。

[0012] Preferably, the concentration of the transition metal mixed solution A in step 4 is 1-10 mol / L; the concentration of the alkali solution is 0.5-8 mol / L; and the concentration of the complexing agent is 2-20 mol / L.

[0013] Preferably, the pH value in step 5 is 8.0-14.0.

[0014] Preferably, the calcination temperature in step 8 is 500-1000 °C.

[0015] The above-mentioned lithium-rich manganese-based substrate cathode material based on pre-oxidation design is used as a cathode in lithium-ion batteries.

[0016] Inventive Principles The present invention provides an oxidized transition metal precursor prepared by a pre-oxidation reaction, which is used to form a lithium-rich manganese-based layered cathode based on pre-oxidation design. This precursor can form a good layered structure and reshaped LiMn6 superstructure units (oxygen redox reaction structural units), thereby suppressing irreversible oxygen release. At the same time, it helps to modulate the morphological transformation behavior of the lithiation process, realizing a single-crystal cathode with high structural stability and mechanical properties, thereby improving the structural and electrochemical stability of the material. Beneficial effects

[0017] Compared with existing technologies, the present invention provides a pre-oxidized lithium-rich manganese-based substrate cathode material, its preparation method, and its application, which have the following significant advantages: The lithium-rich layered cathode material prepared by this invention, based on pre-oxidation, constructs a unique superlattice structure, realizing the intrinsic superstructure design of lithium-rich manganese-based layered cathodes, and significantly improving its discharge specific capacity, cycle performance, and rate performance. Specifically, the pre-oxidized transition metal precursor obtained by the open co-precipitation reaction provided in this application has relatively high valence transition metal ions, which is beneficial for suppressing Li / Ni anti-site mixing during sintering and improving the integrity of the layered structure. At the same time, some high valence transition metal elements can participate in the formation of LiMn6-like superstructures—LiNiMn5 units—in the Li2MnO3 domain, which can fundamentally modulate the anion redox activity and reversibility. In addition, the oxidant source (oxygen) in the air is controllably introduced during the precursor preparation stage, which can improve the bulkiness of its secondary particles and reduce the particle size. This helps the primary particles to continue to grow and peel off during the subsequent lithiation process, forming a single-crystal lithium-rich manganese-based layered cathode, thereby improving the material's cycle, structural stability, and rate performance. Specifically, the pre-oxidized lithium-rich layered cathode, Li (1.2+y) [Ni 0.2 Mn 0.6 ] (0.8-y) / 0.8 O2 (x and y are used to correct for minor deviations between the actual and theoretical chemical formulas), at a 1 C rate (1 C = 250 mA g). -1 Its discharge specific capacity can reach 222 mAh g. -1 After 100 cycles, its capacity retention rate can reach over 96%.

[0018] The open co-precipitation reaction system developed in this invention is easy to mass-produce and can be combined with a subsequent calcination strategy to prepare lithium-rich layered oxides. This method is low-cost, time-saving, and labor-saving, and provides methodological guidance for industrialization.

[0019] The intrinsic superstructure proposed in this invention provides new ideas for the structural design and modification of lithium-rich cathodes in the future. Attached Figure Description

[0020] Figure 1 This is a flowchart of a preparation process for a pre-oxidized lithium-rich manganese-based substrate cathode according to the present invention; Figure 2 XRD pattern of the lithium-rich manganese-based substrate cathode material precursor prepared in Example 1 based on pre-oxidation design; Figure 3 The image shows the XRD pattern of the lithium-rich manganese-based substrate cathode material prepared in Example 1, based on pre-oxidation design. Figure 4 SEM image of the lithium-rich manganese-based substrate cathode material prepared in Example 1 based on pre-oxidation design; Figure 5The image shows the ssNMR spectrum of the lithium-rich manganese-based substrate cathode material prepared in Example 1 based on pre-oxidation design. Figure 6 The first cycle (20 mA g) of the lithium-rich manganese-based substrate cathode material prepared in Example 1 based on pre-oxidation design in the voltage range of 2.0~4.8 V. -1 Charge-discharge curves; Figure 7 Cycling curves (250 mA g) of the lithium-rich manganese-based substrate cathode material prepared in Example 1 based on pre-oxidation design in the voltage range of 2.0–4.8 V. -1 ); Figure 8 SEM image of the lithium-rich manganese-based substrate cathode material prepared in Example 2 based on pre-oxidation design; Figure 9 The first cycle (20 mA g) of the lithium-rich manganese-based substrate cathode material prepared in Example 2 based on pre-oxidation design in the voltage range of 2.0~4.8 V. -1 Charge-discharge curves; Figure 10 Cycling curves (250 mA g) of the lithium-rich manganese-based substrate cathode material prepared in Example 2, based on pre-oxidation design, in the voltage range of 2.0–4.8 V. -1 ); Figure 11 SEM image of the lithium-rich manganese-based substrate cathode material prepared in Example 3 based on pre-oxidation design; Figure 12 The first cycle (20 mA g) of the lithium-rich manganese-based substrate cathode material prepared in Example 3 based on pre-oxidation design in the voltage range of 2.0~4.8 V. -1 Charge-discharge curves; Figure 13 Cycling curves (250 mA g) of the lithium-rich manganese-based substrate cathode material prepared in Example 3, based on pre-oxidation design, in the voltage range of 2.0–4.8 V. -1 ); Figure 14 SEM image of the lithium-rich manganese-based substrate cathode material prepared in Example 4, based on pre-oxidation design; Figure 15 The first cycle (20 mA g) of the lithium-rich manganese-based substrate cathode material prepared in Example 4 based on pre-oxidation design in the voltage range of 2.0~4.8 V. -1 Charge-discharge curves; Figure 16 Cycling curves (250 mA g) of the lithium-rich manganese-based substrate cathode material prepared in Example 4, based on pre-oxidation design, in the voltage range of 2.0–4.8 V. -1 ); Figure 17 XRD pattern of lithium-rich manganese-based substrate cathode material precursor prepared for comparison; Figure 18 XRD patterns of lithium-rich manganese-based substrate cathode materials prepared in comparison; Figure 19 SEM image of the lithium-rich manganese-based substrate cathode material prepared in comparison; Figure 20 The first cycle (20 mAg) of the lithium-rich manganese-based substrate cathode material prepared for comparison in the voltage range of 2.0~4.8 V. -1 Charge-discharge curves; Figure 21 Cycling curves (250 mA g) of the lithium-rich manganese-based substrate cathode material prepared for comparison in the voltage range of 2.0–4.8 V. -1 ). Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to the embodiments. However, it should be noted that the following embodiments are only used to describe the content of the invention and do not constitute a limitation on the scope of protection of the present invention. Example 1

[0022] A pre-oxidized lithium-rich manganese-based substrate cathode material with the molecular formula Li (1.2+y) [Ni 0.2 Mn 0.6 ] (0.8-y) / 0.8 O2, wherein the preparation method of lithium-rich manganese-based basal cathode material is as follows: Figure 1 As shown, an open (air) co-precipitation reaction system was introduced. By adjusting parameters such as the concentration and flow rate of salt, alkali, and complexing agent, as well as the pH of the co-precipitation system, an excellent pre-oxidized lithium-rich cathode precursor was prepared, resulting in a high-performance lithium-rich manganese-based substrate cathode material. The specific steps include: Part 1: The following method was used to prepare a lithium-rich manganese-based substrate cathode material precursor (Ni) based on pre-oxidation design. 0.25 Mn 0.75 (OH) x (x>2): (1) Nickel sulfate hexahydrate and manganese sulfate monohydrate were dissolved in deionized water according to a nickel:manganese molar ratio of 1:3 to prepare a mixed transition metal solution with a mixed metal ion concentration of 4 mol / L. (2) Sodium hydroxide was dissolved in deionized water as an alkali source to prepare a sodium hydroxide solution with a concentration of 4 mol / L; an ammonia solution with a concentration of 6 mol / L was prepared as complexing agent C; (3) Add a 1 mol / L ammonia solution as a base liquid to a co-precipitation reactor in an air atmosphere with a throughput of 2 L / h, the volume of which is 1 / 2 of the total reaction volume; (4) Under a stirring speed of 500 rpm and a heating condition of 55 °C, the above-mentioned transition metal mixed solution, sodium hydroxide solution and ammonia complexing agent are simultaneously pumped into the reactor to continuously carry out the co-precipitation reaction process; (5) The pH of the reaction system is controlled by dynamically controlling the rate of addition of alkali solution, with a pH of 13.0; (6) After the feeding is completed, continue stirring and aging for 10 hours. Place the obtained material in a container for solid-liquid separation, centrifugation and washing, and dry at 60 °C to obtain the pre-oxidized transition metal precursor. Part Two: The following method was used to prepare lithium-rich manganese-based substrate cathode materials (Li) based on pre-oxidation design. (1.2+y) [Ni 0.2 Mn 0.6 ] (0.8-y) / 0.8 O2): (1) Mix 1.43805 g of the above-mentioned pre-oxidized transition metal precursor with 0.88675 g of lithium carbonate to obtain the reaction precursor; (2) Place the powder in a muffle furnace and heat it at 5 °C for 1 minute in an air atmosphere. -1 Pre-calcine at 550 °C for 5 hours; then calcine at 5 °C for 5 minutes. -1 The temperature was gradually increased to 900 °C and sintered for 10 h. After cooling to room temperature, the material was ground to obtain a lithium-rich manganese-based substrate cathode material based on pre-oxidation design. Example 2

[0023] A lithium-rich manganese-based substrate cathode material based on pre-oxidation design, with the molecular formula Li. (1.2+y) [Ni 0.2 Mn 0.6 ] (0.8-y) / 0.8 O2, wherein the preparation method of lithium-rich manganese-based basal cathode material includes the following steps: Part 1: The following method was used to prepare a lithium-rich manganese-based substrate cathode material precursor (Ni) based on pre-oxidation design. 0.25 Mn 0.75 (OH) x (x>2): (1) Nickel sulfate hexahydrate and manganese sulfate monohydrate were dissolved in deionized water according to a nickel:manganese molar ratio of 1:3 to prepare a mixed transition metal solution with a mixed metal ion concentration of 4 mol / L. (2) Sodium hydroxide was dissolved in deionized water as an alkali source to prepare a sodium hydroxide solution with a concentration of 2 mol / L; an ammonia solution with a concentration of 5 mol / L was prepared as complexing agent C; (3) Add a 5 mol / L ammonia solution as a base liquid to a co-precipitation reactor in a completely open air atmosphere, the volume of which is 1 / 2 of the total reaction volume; (4) Under a stirring speed of 500 rpm and a heating condition of 55 °C, the above-mentioned transition metal mixed solution, sodium hydroxide solution and ammonia complexing agent are simultaneously pumped into the reactor to continuously carry out the co-precipitation reaction process; (5) The pH of the reaction system is controlled by dynamically controlling the rate of addition of alkali solution, with a pH of 13.0; (6) After the feeding is completed, continue stirring and aging for 10 hours. Place the obtained material in a container for solid-liquid separation, centrifugation and washing, and dry at 60 °C to obtain the pre-oxidized transition metal precursor. Part Two: The following method was used to prepare Li-based lithium-rich manganese-based substrate cathode material with pre-oxidation design. (1.2+y) [Ni 0.2 Mn 0.6 ] (0.8-y) / 0.8 O2: (1) Mix 1.43805 g of the above-mentioned pre-oxidized transition metal precursor with 0.88675 g of lithium carbonate to obtain the reaction precursor; (2) Place the powder in a muffle furnace and heat it at 5 °C for 1 minute in an air atmosphere. -1 Pre-calcine at 550 °C for 5 hours; then calcine at 5 °C for 5 minutes. -1 The temperature was gradually increased to 850 °C and sintered for 10 h. After cooling to room temperature, the material was ground to obtain a lithium-rich manganese-based substrate cathode material based on pre-oxidation design. Example 3

[0024] A lithium-rich manganese-based substrate cathode material based on pre-oxidation design, with the molecular formula Li. (1.2+y) [Ni 0.2 Mg 0.01 Al 0.01 Mn 0.58 ] (0.8-y) / 0.8 O2, wherein the preparation method of lithium-rich manganese-based basal cathode material includes the following steps: Part 1: The following method was used to prepare a lithium-rich manganese-based substrate cathode material precursor (Ni) based on pre-oxidation design. 0.25 Mg 0.0125 Al 0.0125 Mn 0.725 (OH) x (x>2): (1) According to the molar ratio of nickel:manganese:aluminum:magnesium of 20:58:1:1, nickel sulfate hexahydrate, manganese sulfate monohydrate, aluminum sulfate octahydrate and magnesium sulfate heptahydrate were dissolved in deionized water to prepare a mixed metal solution with a mixed metal ion concentration of 1 mol / L. (2) Sodium hydroxide was dissolved in deionized water as an alkali source to prepare a sodium hydroxide solution with a concentration of 6 mol / L; ammonia water with a concentration of 3 mol / L was prepared as complexing agent C; (3) Add a 3 mol / L ammonia solution as a base liquid to a co-precipitation reactor in an air atmosphere with a throughput of 20 L / h, the volume of which is 1 / 2 of the total reaction volume; (4) Under a stirring speed of 500 rpm and a heating condition of 55 °C, the above-mentioned transition metal mixed solution, sodium hydroxide solution and ammonia complexing agent are simultaneously pumped into the reactor to continuously carry out the co-precipitation reaction process; (5) The pH of the reaction system is controlled by dynamically controlling the rate of addition of alkali solution, with a pH of 12.9; (6) After the feeding is completed, continue stirring and aging for 10 hours. Place the obtained material in a container for solid-liquid separation, centrifugation and washing, and dry at 60 °C to obtain the pre-oxidized transition metal precursor. Part Two: The following method was used to prepare Li-based lithium-rich manganese-based substrate cathode material with pre-oxidation design. (1.2+y) [Ni 0.2 Mg 0.01 Al 0.01 Mn 0.58 ] (0.8-y) / 0.8 O2: (1) Mix 1.99682 g of the above-mentioned pre-oxidized transition metal precursor with 1.34069 g of lithium carbonate to obtain the reaction precursor; (2) Place the powder in a muffle furnace and heat it at 5 °C for 1 minute in an air atmosphere. -1 Pre-calcine at 550 °C for 5 hours; then calcine at 5 °C for 5 minutes. -1 The temperature was gradually increased to 900 °C and sintered for 15 h. After cooling to room temperature, the material was ground to obtain a lithium-rich manganese-based substrate cathode material based on pre-oxidation design. Example 4

[0025] A lithium-rich manganese-based substrate cathode material based on pre-oxidation design, with the molecular formula Li. (1.2+y) [Ni 0.13 Co 0.13 Mn 0.54 ] (0.8-y) / 0.8 O2, wherein the preparation method of lithium-rich manganese-based basal cathode material includes the following steps: Part 1: The following method was used to prepare a lithium-rich manganese-based substrate cathode material precursor (Ni) based on pre-oxidation design. 0.1625 Co 0.1625 Mn 0.675 (OH) x (x>2): (1) Nickel sulfate hexahydrate, cobalt sulfate heptahydrate and manganese sulfate monohydrate were dissolved in deionized water according to the molar ratio of nickel:cobalt:manganese of 13:13:54 to prepare a mixed transition metal solution with a mixed metal ion concentration of 8 mol / L. (2) Sodium hydroxide was dissolved in deionized water as an alkali source to prepare a sodium hydroxide solution with a concentration of 5 mol / L; ammonia water with a concentration of 2 mol / L was prepared as complexing agent C; (3) Add a 1 mol / L ammonia solution as a base liquid to a co-precipitation reactor in an air atmosphere with a throughput of 20 L / h, the volume of which is 1 / 2 of the total reaction volume; (4) Under a stirring speed of 500 rpm and a heating condition of 55 °C, the above-mentioned transition metal mixed solution, sodium hydroxide solution and ammonia complexing agent are simultaneously pumped into the reactor to continuously carry out the co-precipitation reaction process; (5) The pH of the reaction system is controlled by dynamically controlling the rate of addition of alkali solution, with a pH of 13.5; (6) After the feeding is completed, continue stirring and aging for 10 hours. Place the obtained material in a container for solid-liquid separation, centrifugation and washing, and dry at 60 °C to obtain the pre-oxidized transition metal precursor. Part Two: The following method was used to prepare lithium-rich manganese-based substrate cathode materials (Li) based on pre-oxidation design. (1.2+y) [Ni 0.13 Co 0.13 Mn 0.54 ] (0.8-y) / 0.8 O2): (1) Mix 1.35368 g of the above-mentioned pre-oxidized transition metal precursor with 0.88151 g of lithium carbonate to obtain the reaction precursor; (2) Place the powder in a muffle furnace and heat it at 5 °C for 1 minute in an air atmosphere. -1 Pre-calcine at 550 °C for 5 hours; then calcine at 5 °C for 5 minutes. -1 The temperature was gradually increased to 800 °C and sintered for 12 h. After cooling to room temperature, the material was ground to obtain a lithium-rich manganese-based substrate cathode material based on pre-oxidation design.

[0026] Comparative Example 1 A lithium-rich manganese-based substrate cathode material with the molecular formula Li 1.2 Ni 0.2 Mn0.6 The preparation method of O2, lithium-rich manganese-based basal cathode material includes the following steps: Part 1: The lithium-rich manganese-based basaltic cathode material precursor (Ni) is prepared using the following method. 0.25 Mn 0.75 (OH)2): (1) Nickel sulfate hexahydrate and manganese sulfate monohydrate were dissolved in deionized water according to a nickel:manganese molar ratio of 1:3 to prepare a mixed transition metal solution with a mixed metal ion concentration of 4 mol / L. (2) Sodium hydroxide was dissolved in deionized water as an alkali source to prepare a sodium hydroxide solution with a concentration of 4 mol / L; ammonia water with a concentration of 6 mol / L was prepared as complexing agent C; (3) Add a 1 mol / L ammonia solution as a base liquid to a coprecipitation reactor with an argon atmosphere of 2 L / h, the volume of which is 1 / 2 of the total reaction volume; (4) Under a stirring speed of 500 rpm and a heating condition of 55 °C, the above-mentioned transition metal mixed solution, sodium hydroxide solution and ammonia complexing agent are simultaneously pumped into the reactor to continuously carry out the co-precipitation reaction process; (5) The pH of the reaction system is controlled by dynamically controlling the rate of addition of alkali solution, with a pH of 11.5; (6) After the feeding is completed, continue stirring and aging for 10 hours. Place the obtained material in a container for solid-liquid separation, centrifugation and washing, and dry at 60 °C to obtain the pre-oxidized transition metal precursor. Part Two: The following method was used to prepare lithium-rich manganese-based substrate cathode materials (Li) based on pre-oxidation design. 1.2 Ni 0.2 Mn 0.6 O2): (1) Mix 1.43805 g of the above-mentioned pre-oxidized transition metal precursor with 0.88675 g of lithium carbonate to obtain the reaction precursor; (2) Place the powder in a muffle furnace and heat it at 5 °C for 1 minute in an air atmosphere. -1 Pre-calcine at 550 °C for 5 hours; then calcine at 5 °C for 5 minutes. -1 The material was sintered at a gradient temperature of 900 °C for 10 h, cooled to room temperature, and then ground to obtain a lithium-rich manganese-based substrate cathode material.

[0027] Structural characterization X-ray diffraction was used to analyze the transition metal precursor Ni of the pre-oxidized lithium-rich manganese-based substrate cathode material prepared in Example 1. 0.25 Mn 0.75 (OH) xAnd the precursor Ni of the comparative lithium-rich manganese-based substrate cathode material 0.25 Mn 0.75 The structure of (OH)2 was characterized, and the results are as follows: Figure 2 and 17 As shown; furthermore, the lithium-rich manganese-based substrate cathode material Li prepared in Example 1 based on pre-oxidation design... (1.2+y) [Ni 0.2 Mn 0.6 ] (0.8-y) / 0.8 O2 and a comparative example of lithium-rich manganese-based substrate cathode material Li 1.2 Ni 0.2 Mn 0.6 O2 is used for structural characterization, such as Figure 3 and 18 As shown; to further analyze the structural characteristics of the pre-oxidized lithium-rich manganese-based substrate cathode, using 7 The lithium-rich manganese-based substrate cathode material prepared in Example 1 was characterized by solid-state NMR characterization, such as... Figure 5 As shown.

[0028] from Figure 2 The XRD pattern shows that the multi-component transition metal precursor Ni prepared in this invention... 0.25 Mn 0.75 (OH) x It exhibits pre-oxidation characteristics—a composition of transition metal ions in a mixed high / low oxidation state, and the main diffraction peak at 15–25° shows a pair of split peaks, corresponding to hydroxide precipitates of transition metal ions (mainly nickel and manganese) with different valence states; in contrast, Figure 17 Ni, a transition metal precursor in medium proportion 0.25 Mn 0.75 (OH)2 exhibits a single characteristic diffraction peak, which is attributed to a divalent transition metal hydroxide.

[0029] Figure 3 The display shows the pre-oxidized lithium-manganese-rich layered cathode material Li... (1.2+y) [Ni 0.2 Mn 0.6 ] (0.8-y) / 0.8 O2 exhibits a well-defined layered structure and a superlattice peak at 20-30°, corresponding to the characteristic peak of the honeycomb superlattice structure of Li2MnO3. Therefore, it can be proven that the material in Example 1 of this invention is a two-phase structure consisting of a layered LiMO2 phase and a monoclinic Li2MnO3 phase. Figure 18 Showing the proportion of Li 1.2 Ni 0.2 Mn 0.6The structural characteristics of O2 show similar peak positions, which proves that the pre-oxidation treatment did not affect the construction of the layered main structure of the material, but instead was able to reshape the composition and order of the superlattice structure.

[0030] Figure 5 The display shows the pre-oxidized lithium-rich manganese-based substrate cathode Li... (1.2+y) [Ni 0.2 Mn 0.6 ] (0.8-y) / 0.8 Lithium ions in O2 exhibit two distribution positions, located in the alkali metal layer (Li₂) at 500-1000 ppm. AM ) and 1200-1750ppm -- transition metal layer (Li TM Specifically, two significant characteristic peaks were observed in the lithium in the transition metal layer, indicating that lithium exists in two specific chemical environments: LiMn6 and LiNiMn5 superstructure units. Unlike the single LiMn6 superstructure possessed by traditional lithium-rich cathodes, the above results confirm that the pre-oxidation design strategy helps to adjust the chemical state of nickel ions, thereby achieving compositional adjustment of the anion redox reaction unit—the superlattice structure—and thus improving the structural and electrochemical properties of lithium-rich cathodes.

[0031] The morphology of the pre-oxidized lithium-rich manganese-based substrate cathode materials prepared in Examples 1, 2, 3, and 4, as well as the comparative lithium-rich manganese-based substrate cathode materials, was characterized using scanning electron microscopy. Figure 4 As shown in 8, 11, 14 and 19.

[0032] from Figure 4 It can be obtained that the pre-oxidized lithium-rich manganese-based layered cathode material Li prepared by the preparation method of the present invention is... (1.2+y) [Ni 0.2 Mn 0.6 ] (0.8-y) / 0.8 O2 exhibits a nanoscale single-crystal primary particle morphology with uniform particle size.

[0033] Figure 8 This invention demonstrates the preparation of a lithium-rich manganese-based substrate cathode material, Li, based on pre-oxidation design, using the preparation method of this invention. (1.2+y) [Ni 0.2 Mn 0.6 ] (0.8-y) / 0.8 The O2 exhibits a relatively dispersed single-crystal primary particle morphology, which proves that under the pre-oxidation system, reasonable control of pH and complexation reaction can successfully adjust the particle dispersion.

[0034] Figure 11 and 14 This invention demonstrates the preparation of a lithium-rich manganese-based substrate cathode material, Li, based on pre-oxidation design, using the preparation method of this invention. (1.2+y) [Ni0.2 Mg 0.01 Al 0.01 Mn 0.58 ] (0.8-y) / 0.8 O2 and Li (1.2+y) [Ni 0.13 Co 0.13 Mn 0.54 ] (0.8-y) / 0.8 O2 also exhibits a relatively dispersed single-crystal primary particle morphology. Despite the different elemental composition compared to Examples 1 and 2, this lithium-rich cathode can still achieve a single-crystal morphology, which confirms the universality of the preparation method described in this invention.

[0035] Figure 19 The comparison shows a lithium-rich manganese-based substrate cathode, Li. 1.2 Ni 0.2 Mn 0.6 O2 exhibits typical micron-sized secondary spherical polycrystalline particles, which inherits the morphological characteristics of spherical precursors obtained by the traditional non-oxidative coprecipitation method. Electrochemical performance testing Test method:

[0036] First, the prepared lithium-rich layered oxide is mixed with a conductive agent (Super P) and a binder (PVDF) in a mass ratio of 7:2:1. After thorough grinding, an appropriate amount of N-methyl-di-ethylpyrrolidone (NMP) is added as a solvent. After stirring, the mixture is coated onto an aluminum foil current collector and dried in a vacuum oven at 90 °C.

[0037] Next, after drying, the aluminum foil is cut into round pieces (Φ=11mm), and the weight is recorded. Then, the electrodes are assembled in the following order: positive electrode shell, electrode, separator, lithium sheet, gasket, spring, and negative electrode shell, to form a button cell.

[0038] Finally, the electrochemical performance was tested at room temperature using the Blue Electric testing system.

[0039] The constant current charge-discharge test conditions are as follows: voltage range of 2.0~4.8 V, and two cycles of small current activation (20 mA g). -1 The test performance results are as follows: Figure 6 As shown in 9, 12, 15, and 20; then, a large current (250 mA g) was applied. -1 Constant current cycling test, test results are as follows: Figure 7 As shown in 10, 13, 16 and 21.

[0040] Figure 6 The lithium-rich manganese-based substrate cathode material Li prepared in Example 1 based on pre-oxidation design (1.2+y) [Ni 0.2 Mn 0.6 ](0.8-y) / 0.8 The initial charge-discharge curve of O2 exhibits typical characteristics of lithium-rich materials, namely, the initial charging curve consists of a ramp region (<4.5 V) and a plateau region (>4.5 V), corresponding to the oxidation compensation of multi-element transition metal ions and lattice oxygen, respectively. Specifically, this pre-oxidized lithium-rich manganese-based cathode material achieves an initial discharge specific capacity as high as 278 mAh g⁻¹. -1 .

[0041] Figure 9 The lithium-rich manganese-based substrate cathode material Li prepared in Example 2 based on pre-oxidation design (1.2+y) [Ni 0.2 Mn 0.6 ] (0.8-y) / 0.8 O2 at 20 mA g -1 The electrochemical curves obtained from constant current charge-discharge tests show a similar "S"-shaped charging curve, with a discharge specific capacity of 263 mAh g. -1 .

[0042] Figure 12 and 15 The lithium-rich manganese-based substrate cathode materials Li prepared in Examples 3 and 4 based on pre-oxidation design (1.2+y) [Ni 0.2 Mg 0.01 Al 0.01 Mn 0.58 ] (0.8-y) / 0.8 O2 and Li (1.2+y) [Ni 0.13 Co 0.13 Mn 0.54 ] (0.8-y) / 0.8 O2 at 20 mA g -1 Electrochemical curves at current densities showed discharge specific capacities of 290 and 226 mAh g, respectively. -1 .

[0043] Figure 20 Li-rich manganese-based substrate cathode material prepared for comparison 1.2 Ni 0.2 Mn 0.6 The first charge-discharge curve of O2 shows a discharge specific capacity of 260 mAh g. -1 Compared to Figure 6 The above experimental results demonstrate that pre-oxidation design can improve the discharge specific capacity of lithium-rich materials. This is mainly because the reshaped superlattice domains under this condition can significantly improve the reversibility of oxygen reaction.

[0044] Figure 7 The lithium-rich manganese-based substrate cathode material Li prepared in Example 1 based on pre-oxidation design (1.2+y) [Ni 0.2 Mn0.6 ] (0.8-y) / 0.8 The cycling performance curve of O2 at 250 mA g -1 The discharge specific capacity at current density is 222 mAh / g, and its cycle retention rate reaches 96.4% after 100 charge-discharge cycles.

[0045] Figure 10 The lithium-rich manganese-based substrate cathode material Li prepared in Example 2 based on pre-oxidation design (1.2+y) [Ni 0.2 Mn 0.6 ] (0.8-y) / 0.8 The discharge specific capacity of O2 is 199 mAh / g, and its retention rate is 93.5% after 100 charge-discharge cycles.

[0046] Figure 13 and 16 The lithium-rich manganese-based substrate cathode materials Li prepared in Examples 3 and 4 based on pre-oxidation design (1.2+y) [Ni 0.2 Mg 0.01 Al 0.01 Mn 0.58 ] (0.8-y) / 0.8 O2 and Li (1.2+y) [Ni 0.13 Co 0.13 Mn 0.54 ] (0.8-y) / 0.8 O2 at 250 mA g -1 Cyclic performance at current densities, with discharge specific capacities of 182 and 175 mAh g, respectively. -1 The retention rates were 90.1% and 95.4%, respectively.

[0047] Figure 21 The comparative preparation of lithium-rich manganese-based substrate cathode material Li1 is presented. 1.2 Ni 0.2 Mn 0.6 The cycling curve of O2 shows a discharge specific capacity of 175 mAh g. -1 Furthermore, the retention rate was only 82.2%. Comparison shows that the pre-oxidation-based preparation method proposed in this invention can significantly optimize the rate performance of the material and adjust the lattice oxygen reversibility of the lithium-rich cathode, thereby improving the cycle stability of the material. In addition, the grain boundary-free single-crystal particles obtained by pre-oxidation can suppress interfacial reactions between the electrode and the electrolyte, and also improve the structural and mechanical stability of the material during electrochemical processes to a certain extent.

[0048] In summary, the lithium-rich layered oxide cathode material prepared by this invention, based on pre-oxidation, reconstructs a highly stable superlattice structure. This directly relates to and influences the performance characteristics of the lattice oxygen redox reaction, thereby improving the reversibility and activity of intrinsic oxygen behavior. Furthermore, the pre-oxidized precursor spontaneously grows after lithiation to obtain a lithium-rich manganese-based cathode material with a single-crystal morphology. This grain boundary-free property significantly improves the structural stability of the material. These design features greatly enhance the discharge specific capacity and cycle stability of the lithium-rich material. In addition, the open co-precipitation reaction system used in this invention is simple to operate, has no atmosphere limitations, and, combined with a simple and efficient high-temperature solid-state method for synthesizing lithium-rich layered cathodes, greatly reduces costs and saves time and effort, demonstrating promising market prospects.

Claims

1. A pre-oxidized lithium-rich manganese-based substrate cathode material, characterized in that, A lithium-based multi-element oxide derived from a transition metal precursor obtained through a pre-oxidation reaction, wherein the main transition metal element is a mixture of at least two of Ni, Co, and Mn.

2. The lithium-rich manganese-based substrate cathode material according to claim 1, characterized in that, The pre-oxidized lithium-rich manganese-based substrate cathode material further includes one or more doping elements selected from B, Na, Mg, Al, P, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Sb, Zr, Nb, Mo, or W.

3. A method for preparing a lithium-rich manganese-based substrate cathode material based on any one of claims 1-2, characterized in that, Includes the following steps: Step 1: Mix at least two transition metal ion sources with water to obtain a transition metal mixed solution A; Step 2: Mix the alkali source with water to prepare alkali solution B; and prepare complexing agent C; Step 3: Add an ammonia solution as the reaction base liquid to a co-precipitation reactor with an adjustable atmosphere. Step 4: The transition metal mixed solution A, alkaline solution B and complexing agent C are simultaneously pumped into the above coprecipitation reactor, heated and stirred to form a dynamic high-temperature reaction system; Step 5: Control the pH of the reaction system to ensure a uniform and orderly coprecipitation reaction and nucleation growth process; Step 6: After feeding is completed, age for several hours, place the obtained material in a container for solid-liquid separation, centrifugal washing, and high-temperature drying to obtain pre-oxidized transition metal precursor D; Step 7: Mix the pre-oxidized transition metal precursor D and lithium source E uniformly according to the molar ratio to obtain the reaction precursor; Step 8: Place the reaction precursor in a high-temperature furnace and calcine it at high temperature for several hours under a set atmosphere to obtain the lithium-rich manganese-based substrate cathode material based on pre-oxidation design.

4. The method for preparing lithium-rich manganese-based substrate cathode material based on pre-oxidation design according to any one of claims 3, characterized in that, The alkaline solution B mentioned in step 2 is one or more of sodium carbonate or sodium hydroxide; the complexing agent C is ammonia.

5. The method for preparing a lithium-rich manganese-based substrate cathode material based on pre-oxidation design according to any one of claims 3, characterized in that, The reactor environment described in step 3 is either a completely open system or a gas flow controllable environment; the atmosphere is air; if it is a gas flow controllable environment, the air flow rate m ranges from 0. <m<50 L / h。 6. The method for preparing lithium-rich manganese-based basal cathode material based on pre-oxidation design according to any one of claims 3, characterized in that, The concentration of the transition metal mixed solution A mentioned in step 4 is 1-10 mol / L; the concentration of the alkali solution is 0.5-8 mol / L; and the concentration of the complexing agent is 2-20 mol / L.

7. The method for preparing lithium-rich manganese-based substrate cathode material based on pre-oxidation design according to any one of claims 3, characterized in that, The pH value in step 5 is 8.0-14.

0.

8. The method for preparing lithium-rich manganese-based basal cathode material based on pre-oxidation design according to any one of claims 3, characterized in that, The calcination temperature mentioned in step 8 is 500-1000 °C.

9. The application of the lithium-rich manganese-based substrate cathode material prepared by any one of the preparation methods in claims 3-8 as a cathode in lithium-ion batteries.

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