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

Abstract

This disclosure belongs to the field of lithium battery technology, specifically relating to a lithium-rich manganese-based cathode material, its preparation method, and its application. By high-temperature coating of a manganese-containing first coating layer onto the surface of the lithium-rich manganese-based cathode material, the surface is enriched with manganese, controlling the distribution of the two phases and making the matrix element distribution more uniform, reducing the probability of phase transition during high-temperature coating. Subsequently, a second coating layer is formed by coating with elements such as Al, Zr, Sr, Ti, and Mg, thereby improving capacity, maintaining structural stability, and increasing cycle life under high-rate conditions.

Description

Technical Field

[0001] This disclosure belongs to the technical field of lithium batteries. Specifically, it relates to a lithium-rich manganese-based cathode material, its preparation method and application. Background Art

[0002] At present, lithium-ion batteries (LIBs) have been widely used in pure electric vehicles and hybrid electric vehicles. However, the energy density of the most advanced lithium batteries is also limited, which directly affects the driving range of the vehicle between two charges and is one of the main problems hindering their practical application. Compared with traditional cathode materials such as LCO (LiCoO2) and LFP (LiFePO4), the lithium-rich manganese-based cathode material xLi2MnO3·(1-x)LiTMO2 (0 < x < 1, transition metal (TM) = Ni, Co, Mn, etc.) has the advantages of high voltage, stable structure, low cost, etc., and also has a significant capacity advantage, exceeding 250 mAh / g in the voltage range of 2.0V - 4.8V, showing great promise in the next-generation high-energy-density lithium-ion batteries (LIBs).

[0003] In the lithium-rich manganese-based cathode material (LLOs), the Li2MnO3 component is not only the source of high-capacity characteristics but also the guarantee of structural stability at high working voltages. At a voltage of 4.55V, Li2MnO3 will be activated to provide most of the capacity, and the activation of Li2MnO3 has a crucial impact on the electrochemical performance of the lithium-rich manganese-based cathode material. This prompts us to think about the role played by the LiMO2 structure as another component of the lithium-rich manganese-based cathode material and what the internal relationship between these two components is. The LiMO2 component can be used alone as a nickel-rich cathode material for lithium-ion batteries. Because Li2MnO3 inhibits the continuous expansion of the lattice parameter c and the contraction of the lattice parameter a, the LiMO2 cathode has a rapid capacity decay at high working voltages. These phenomena indicate that there is a synergistic effect between the two parts in LLOs, and the distribution of the two components will affect the performance of LLOs. Therefore, the research on the distribution law and electrochemical mechanism of the two-phase composition has received extensive attention. Although the distribution of these two components has a profound impact on the electrochemical performance of LLOs, its regulation is still challenging.

[0004] In recent years, researchers have improved the capacity and cycle stability through strategies such as coating and doping. However, the problem that the distribution of the two components in the matrix is uneven and the phase transformation occurs during the second calcination at high temperature is still inevitable, which will lead to problems such as voltage drop and capacity decline. To solve this problem, researchers have enriched nickel on the surface through a large number of measures, regulated the content and component ratio of each element in the lithium-rich manganese-based cathode material, which can also effectively improve the electrochemical performance of the material. However, at high rates, the side reaction between nickel ions and the electrolyte is aggravated, and due to Ni 2+ and Li +The ionic radii are similar, Ni 2+ Easier migration, which is beneficial for interlayer Li + Migration has adverse effects. In addition, Ni element is prone to side reactions with electrolyte, forming a nickel-rich layer on the material surface, which hinders the insertion and extraction of lithium ions, deteriorates the material performance, and leads to poor performance at high rates.

[0005] Therefore, current methods for improving lithium-rich manganese-based cathode materials cannot effectively enhance the reversible specific capacity and cycle stability at high rates.

[0006] In view of this, this disclosure is hereby made. Summary of the Invention

[0007] The purpose of this disclosure is to provide a lithium-rich manganese-based cathode material, its preparation method and application, which aims to effectively improve the material's reversible specific capacity and cycling stability at high rates.

[0008] To achieve the above-mentioned objectives of this disclosure, the following technical solutions may be adopted:

[0009] The solution provided in this disclosure includes a lithium-rich manganese-based cathode material, comprising a lithium-rich manganese-based substrate, wherein a first coating layer and a second coating layer are sequentially coated on the lithium-rich manganese-based substrate, and the first coating layer is located between the lithium-rich manganese-based substrate and the second coating layer.

[0010] The coating element in the first coating layer is Mn, and the coating element in the second coating layer is selected from at least one of Al, Zr, Sr, Ti and Mg.

[0011] In some embodiments of this disclosure, the chemical formula of the lithium-rich manganese-based substrate is: xLi2MnO3·(1-x)LiTMO2, 0.4≤x≤0.8, where TM represents at least one of Ni and Mn.

[0012] In some embodiments of this disclosure, the first coating layer is a manganese oxide coating layer.

[0013] In some embodiments of this disclosure, the mass ratio of the first coating layer to the lithium-rich manganese-based substrate is (0.1-2.0):100.

[0014] In some embodiments of this disclosure, the second coating layer is selected from at least one of oxides, phosphates, and fluorides.

[0015] In some embodiments of this disclosure, the mass ratio of the second coating layer to the lithium-rich manganese-based substrate is (0.1-0.5):100.

[0016] In some embodiments of this disclosure, the coating element in the second coating layer is selected from at least one of Al and Zr.

[0017] The scheme provided in this disclosure also includes a method for preparing a lithium-rich manganese-based cathode material, comprising: sequentially forming a first coating layer and a second coating layer on a lithium-rich manganese-based substrate.

[0018] In some embodiments of this disclosure, a lithium-rich manganese-based substrate is mixed and sintered with a first coating material to obtain an intermediate product, and the intermediate product is mixed and sintered with a second coating material; wherein the first coating material is a manganese source, and the second coating material contains the coating elements in the second coating layer.

[0019] In some embodiments of this disclosure, the first coating material is selected from at least one of manganese oxides, manganese hydroxides, and manganese hydroxyoxides.

[0020] In some embodiments of this disclosure, the mass ratio of the first coating material to the lithium-rich manganese-based substrate is (0.1-2.0):100.

[0021] In some embodiments of this disclosure, the sintering temperature of the lithium-rich manganese-based substrate and the first coating material is 600℃-900℃, and the sintering time is 5h-12h.

[0022] In some embodiments of this disclosure, after the lithium-rich manganese-based substrate and the first coating material are sintered, the mixture is cooled to room temperature to obtain an intermediate product.

[0023] In some embodiments of this disclosure, the mass ratio of the second coating material to the lithium-rich manganese-based substrate is (0.1-0.5):100.

[0024] In some embodiments of this disclosure, the second coating material is selected from at least one of oxides, phosphates, and fluorides.

[0025] In some embodiments of this disclosure, the sintering temperature of the intermediate product and the second coating material is 600℃-800℃, and the sintering time is 5h-8h.

[0026] In some embodiments of this disclosure, after the intermediate product and the second coating material are sintered, the mixture is cooled to room temperature.

[0027] In some embodiments of this disclosure, the preparation process of the lithium-rich manganese-based substrate includes: mixing and sintering a hydroxide precursor and a lithium salt, wherein the hydroxide precursor contains manganese and nickel elements.

[0028] In some embodiments of this disclosure, the sintering temperature of the hydroxide precursor and the lithium salt is 750°C-950°C, and the sintering time is 8h-15h.

[0029] In some embodiments of this disclosure, the molar ratio of lithium element to the total amount of metal element in the hydroxide precursor is (1.1-1.6):1 by controlling the amount of hydroxide precursor and lithium salt.

[0030] In some embodiments of this disclosure, the chemical formula of the hydroxide precursor is Ni y Mn 1-y (OH)2, where y = 0.2-0.6.

[0031] In some embodiments of this disclosure, the hydroxide precursor is prepared by a co-precipitation method.

[0032] In some embodiments of this disclosure, the hydroxide precursor and lithium salt are sintered under an oxygen-containing atmosphere, and then cooled to room temperature after sintering.

[0033] The solution provided in this disclosure also includes a positive electrode sheet, comprising the lithium-rich manganese-based positive electrode material described in the above embodiments.

[0034] The solution provided in this disclosure also includes a lithium battery, comprising the positive electrode sheet in the above embodiments.

[0035] The solution provided in this disclosure also includes an electrical device comprising the lithium battery described in the above embodiments.

[0036] By coating a first coating layer containing manganese at high temperature onto the surface of a lithium-rich manganese-based cathode material, the surface is enriched with manganese, and the distribution of the two phases is controlled, making the distribution of matrix elements more uniform and reducing the probability of phase transition during high-temperature coating. Subsequently, at least one element such as Al, Zr, Sr, Ti, and Mg is coated to form a second coating layer, thereby improving capacity and maintaining structural stability, and improving cycle life under high-rate conditions. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 A process flow diagram of the preparation method is provided for this disclosure;

[0039] Figure 2 The image shows the SEM image of the product prepared in Example 1.

[0040] Figure 3 SEM image of the product prepared in Comparative Example 1;

[0041] Figure 4 The image shows the SEM image of the product prepared in Comparative Example 2. Detailed Implementation

[0042] The embodiments of this disclosure will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of this disclosure. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0043] The endpoints and any values ​​of the ranges disclosed in this disclosure are not limited to the precise ranges or values, and such ranges or values ​​should be understood to include values ​​close to such ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed herein.

[0044] This disclosure provides a method for preparing a lithium-rich manganese-based cathode material. Please refer to [link / reference]. Figure 1 This includes: sequentially forming a first coating layer and a second coating layer on a lithium-rich manganese-based substrate, specifically including the following steps:

[0045] S1. Preparation of lithium-rich manganese-based substrate

[0046] The preparation process of the lithium-rich manganese-based substrate includes: uniformly mixing a hydroxide precursor and a lithium salt, followed by a single sintering to obtain a sintered product. The hydroxide precursor contains manganese and nickel elements, and sintering forms a cathode material substrate with the following chemical formula:

[0047] The chemical formula of the lithium-rich manganese-based substrate is: xLi2MnO3·(1-x)LiTMO2, where 0.4≤x≤0.8, and TM represents Ni and Mn, which can be any one or more of them. Specifically, the value of x is 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, etc.

[0048] In some embodiments of this disclosure, the chemical formula of the hydroxide precursor is Ni y Mn 1-y (OH)₂, where y = 0.2-0.6, and y can take values ​​of 0.2, 0.3, 0.4, 0.5, 0.6, etc. The hydroxide precursor can be prepared by co-precipitation. The specific preparation process can refer to existing technologies, and the main steps include: passing nickel salt and manganese salt into a reactor, and co-precipitating under the action of a precipitant and a complexing agent.

[0049] In some embodiments of this disclosure, by controlling the amounts of the hydroxide precursor and lithium salt, the molar ratio of lithium element to the total amount of metal elements in the hydroxide precursor is (1.1-1.6):1, to form a lithium-rich manganese-based substrate. Specifically, the molar ratio of lithium element to the total amount of metal elements in the hydroxide precursor can be 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, etc.

[0050] In some embodiments of this disclosure, the sintering temperature for a single sintering is 750℃-950℃, the sintering time is 8h-15h, the sintering process is carried out in an oxygen-containing atmosphere, such as an air atmosphere or an oxygen atmosphere, and after sintering is completed, the product is cooled to room temperature to obtain the sintered product.

[0051] Specifically, the sintering temperature for a single sintering can be 750℃, 800℃, 850℃, 900℃, 950℃, etc.; the sintering time can be 8h, 10h, 12h, 15h, etc.

[0052] S2, Forming the first coating layer

[0053] The lithium-rich manganese-based substrate (i.e., the sintered product obtained in S1) is mixed evenly with the first coating material and then sintered twice to obtain an intermediate product. The first coating material is a manganese source, and the intermediate product is a lithium-rich manganese-based cathode layer material coated with manganese oxide.

[0054] In some embodiments of this disclosure, the first coating material is selected from at least one of manganese oxide, manganese hydroxide, and manganese hydroxyl oxide, and can be any one or more of the above. By controlling the amount of the first coating material, the mass ratio of the first coating material to the lithium-rich manganese-based substrate is (0.1-2.0):100, so that the amount of manganese coating is more suitable, which can achieve the purpose of regulating the two-phase distribution and making the matrix element distribution more uniform.

[0055] Specifically, the mass ratio of lithium-rich manganese-based substrate to the first coating material can be 0.1:100, 0.5:100, 1.0:100, 1.5:100, 2.0:100, etc.

[0056] Furthermore, the secondary sintering temperature is 600℃-900℃, and the sintering time is 5h-12h. By controlling the sintering temperature and time, a uniform coating of manganese is formed. After sintering is completed, the product is cooled to room temperature to obtain the intermediate product.

[0057] Specifically, the sintering temperature for secondary sintering can be 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, etc.; the sintering time can be 5h, 8h, 10h, 12h, etc.

[0058] S3, Forming the second coating layer

[0059] The intermediate product obtained in step S2 is mixed evenly with the second coating material and then sintered three times. The second coating material contains the coating elements of the second coating layer, namely Al, Zr, Sr, Ti, and Mg. Because nickel reacts with the electrolyte, a nickel-rich layer forms on the material surface, which can affect the product's capacity and stability. This disclosure addresses this issue by forming a second coating layer to reduce the surface Ni content. 2+ The mass fraction is beneficial for maintaining structural stability and increasing capacity.

[0060] In some embodiments of this disclosure, the second coating material is selected from at least one of oxides, phosphates, and fluorides, and can be any one or more of them. Specifically, when the coating element is Al, the second coating material can be alumina, aluminum phosphate, aluminum fluoride, etc.

[0061] Furthermore, the mass ratio of the second coating material to the lithium-rich manganese-based substrate is (0.1-0.5):100, such as 0.1:100, 0.2:100, 0.3:100, 0.4:100, 0.5:100, etc.

[0062] Furthermore, the sintering temperature for the three sintering processes is 600℃-800℃, and the sintering time is 5h-8h, in order to form a uniform second coating layer, which significantly improves the electrochemical performance of the cathode material. After sintering is complete, the material is cooled to room temperature.

[0063] Specifically, the sintering temperature for three sintering processes can be 600℃, 650℃, 700℃, 750℃, 800℃, etc.; the sintering time can be 5h, 6h, 7h, 8h, etc.

[0064] This disclosure also provides a lithium-rich manganese-based cathode material, comprising a lithium-rich manganese-based substrate, on which a first coating layer and a second coating layer are sequentially coated, with the first coating layer located between the lithium-rich manganese-based substrate and the second coating layer; wherein the coating element in the first coating layer is Mn, and the coating element in the second coating layer is selected from at least one of Al, Zr, Sr, Ti, and Mg. This lithium-rich manganese-based cathode material can be prepared by the above-described preparation method.

[0065] In a preferred embodiment of this disclosure, the coating element in the second coating layer is selected from at least one of Al and Zr. By optimizing the coating element, the electrochemical performance of the product can be further improved.

[0066] In some embodiments of this disclosure, the mass ratio of the first coating layer to the lithium-rich manganese-based substrate is (0.1-2.0):100, and the mass ratio of the second coating layer to the lithium-rich manganese-based substrate is (0.1-0.5):100. By optimizing the quality of the coating layers, the electrochemical performance of the final product can be further improved.

[0067] In some embodiments of this disclosure, the first coating layer is a manganese oxide coating layer; the second coating layer is selected from at least one of oxides, phosphates and fluorides, that is, the second coating layer can be an oxide, phosphate or fluoride containing a coating element, etc.

[0068] This disclosure also provides a positive electrode sheet, including the lithium-rich manganese-based positive electrode material in the above embodiments, and may further include a positive current collector, wherein the lithium-rich manganese-based positive electrode material serves as an active coating on the positive current collector.

[0069] This disclosure also provides a lithium battery, including the positive electrode sheet described in the above embodiments, and may further include a negative electrode sheet, an electrolyte, a separator, etc., to form a complete lithium battery structure. Improving the lithium-rich manganese-based positive electrode material can enhance the electrochemical performance of the positive electrode sheet, thereby improving the electrochemical performance of the lithium battery.

[0070] This disclosure also provides an electrical device, including the lithium battery described in the above embodiments, and may also include electrical appliances, etc., using the lithium battery to supply power to the electrical appliances, and the specific type of electrical appliances is not limited.

[0071] The features and performance of this disclosure will be further described in detail below with reference to embodiments.

[0072] Example 1

[0073] This embodiment provides a method for preparing a lithium-rich manganese-based cathode material, including the following steps:

[0074] (1) Ni prepared by coprecipitation method 0.35 Mn 0.65 (OH)2 precursor, the specific operation steps are as follows:

[0075] Add 500 mL of water to the reactor, then add 10 mol / L sodium hydroxide solution and 5 mol / L ammonia solution to form a base solution. Control the ammonia concentration of the base solution to 5 mol / L and the pH value to 10-12.

[0076] Nickel sulfate solution and manganese sulfate solution were mixed at a nickel-manganese molar ratio of 0.35:0.65 to obtain a mixed salt solution with a total nickel-manganese concentration of 2 mol / L. The mixed salt solution, 10 mol / L sodium hydroxide solution and 5 mol / L ammonia solution were introduced into the bottom liquid of the reactor for co-precipitation reaction. The ammonia concentration of the system was controlled at 5 mol / L, the pH value was 10-12, and the flow rate of the mixed salt solution was 50 ml / min to obtain a precursor with a particle size of 3-9 μm.

[0077] (2) Take the Ni obtained in step (1) 0.35 Mn 0.65( The OH)2 precursor and Li2CO3 powder were mixed evenly at a molar ratio of lithium to nickel and manganese of 1.3, and then sintered at 850°C for 15 hours in air atmosphere. After cooling to room temperature, a sintered product was obtained.

[0078] (3) The calcined product obtained in step (2) is mixed with 0.5% manganese oxide (i.e., the mass ratio of manganese oxide to calcined product is 0.5:100). The mixed sample is sintered at 800°C for 8 hours in an air atmosphere. After cooling to room temperature, the lithium-rich manganese-based cathode material coated with manganese oxide can be obtained.

[0079] (4) Mix the product obtained in step (3) with 0.20% alumina (i.e., the mass ratio of alumina to the product of the first sintering is 0.2:100), and sinter the mixed sample at 600°C for 5 hours in an air atmosphere. After cooling to room temperature, the lithium-rich manganese-based cathode material coated with alumina can be obtained.

[0080] Performance testing: The prepared lithium-rich manganese-based cathode material, conductive carbon and binder were mixed in a ratio of 90:5:5 to form a slurry. The slurry was then coated on aluminum foil, dried, rolled and cut into sheets, and finally assembled with lithium sheets to form a coin cell. The test range was 2.3V-4.55V.

[0081] Test results: As shown in Table 1, the sample of Example 1 has a discharge specific capacity of 236.7 mAh / g at a current density of 0.1C and an initial coulombic efficiency of up to 87.0%.

[0082] Example 2

[0083] This embodiment provides a method for preparing a lithium-rich manganese-based cathode material, including the following steps:

[0084] (1) Ni prepared by coprecipitation method 0.35 Mn 0.65 (OH)2 precursor, the preparation process is as described in Example 1.

[0085] (2) Take the Ni obtained in step (1)0.35 Mn 0.65 The (OH)2 precursor and Li2CO3 powder were mixed evenly at a molar ratio of lithium to nickel and manganese of 1.3. The mixture was then sintered at 850°C for 15 hours in air and cooled to room temperature to obtain the sintered product.

[0086] (3) The calcined product obtained in step (2) is mixed with 1% manganese hydroxyl oxide (i.e., the mass ratio of manganese hydroxyl oxide to calcined product is 1.0:100). The mixed sample is sintered at 850°C for 6 hours in an air atmosphere. After cooling to room temperature, the lithium-rich manganese-based cathode material coated with manganese oxide can be obtained.

[0087] (4) Mix the product obtained in step (3) with 0.30% zirconium phosphate (the mass ratio of zirconium phosphate to the sintered product is 0.3:100). Sinter the mixed sample at 750°C for 5 hours in air atmosphere. After cooling to room temperature, the lithium-rich manganese-based cathode material coated with zirconium phosphate can be obtained.

[0088] Performance testing: Lithium-rich manganese-based cathode material, conductive carbon, and binder were mixed in a ratio of 90:5:5 to form a slurry. The slurry was then coated onto aluminum foil, dried, rolled, and cut into sheets. Finally, it was assembled with lithium foil to form a coin cell. The test range was 2.3V-4.55V.

[0089] Test results: As shown in Table 1, the discharge specific capacity of the sample in Example 2 at a current density of 0.1C is 234.8mAh / g, and the initial coulombic efficiency is as high as 86.6%.

[0090] Example 3

[0091] This embodiment provides a method for preparing a lithium-rich manganese-based cathode material, including the following steps:

[0092] (1) Ni prepared by coprecipitation method 0.35 Mn 0.65 (OH)2 precursor, the preparation process is as described in Example 1.

[0093] (2) Take the Ni obtained in step (1) 0.35 Mn 0.65 The (OH)2 precursor and Li2CO3 powder were mixed evenly at a molar ratio of lithium to nickel and manganese of 1.3. The mixture was then sintered at 850°C for 15 hours in air and cooled to room temperature to obtain the sintered product.

[0094] (3) The calcined product obtained in step (2) is mixed with 1% manganese hydroxide (i.e., the mass ratio of manganese hydroxide to calcined product is 1.0:100). The mixed sample is sintered at 800°C for 5 hours in air atmosphere. After cooling to room temperature, the lithium-rich manganese-based cathode material coated with manganese oxide can be obtained.

[0095] (4) Mix the product obtained in step (3) with 0.30% strontium fluoride (the mass ratio of strontium fluoride to the sintered product is 0.3:100). Sinter the mixed sample at 700°C for 5 hours in an air atmosphere. After cooling to room temperature, the lithium-rich manganese-based cathode material coated with strontium fluoride can be obtained.

[0096] Performance testing: Lithium-rich manganese-based cathode material, conductive carbon, and binder were mixed in a ratio of 90:5:5 to form a slurry. The slurry was then coated onto aluminum foil, dried, rolled, and cut into sheets. Finally, it was assembled with lithium foil to form a coin cell. The test range was 2.3V-4.55V.

[0097] Test results: As shown in Table 1, the sample of Example 3 has a discharge specific capacity of 234.6 mAh / g at a current density of 0.1C and an initial coulombic efficiency of up to 86.6%.

[0098] Example 4

[0099] This embodiment provides a method for preparing a lithium-rich manganese-based cathode material, including the following steps:

[0100] (1) Ni prepared by coprecipitation method 0.35 Mn 0.65 (OH)2 precursor, the preparation process is as described in Example 1.

[0101] (2) Take the Ni obtained in step (1) 0.35 Mn 0.65 The (OH)2 precursor and Li2CO3 powder were mixed evenly at a molar ratio of lithium to nickel and manganese of 1.3. The mixture was then sintered at 850°C for 15 hours in air and cooled to room temperature to obtain the sintered product.

[0102] (3) The calcined product obtained in step (2) is mixed with 0.5% manganese oxide (i.e., the mass ratio of manganese oxide to calcined product is 0.5:100). The mixed sample is sintered at 850°C for 8 hours in air atmosphere. After cooling to room temperature, the lithium-rich manganese-based cathode material coated with manganese oxide can be obtained.

[0103] (4) Mix the product obtained in step (3) with 0.25% aluminum phosphate (the mass ratio of aluminum phosphate to the product of the first sintering is 0.25:100). Sinter the mixed sample at 600°C for 5 hours in air atmosphere. After cooling to room temperature, the lithium-rich manganese-based cathode material coated with aluminum phosphate can be obtained.

[0104] Performance testing: Lithium-rich manganese-based cathode material, conductive carbon, and binder were mixed in a ratio of 90:5:5 to form a slurry. The slurry was then coated onto aluminum foil, dried, rolled, and cut into sheets. Finally, it was assembled with lithium foil to form a coin cell. The test range was 2.3V-4.55V.

[0105] Test results: As shown in Table 1, the sample of Example 4 has a discharge specific capacity of 235.3 mAh / g at a current density of 0.1C and an initial coulombic efficiency of up to 86.8%.

[0106] Example 5

[0107] This embodiment provides a method for preparing a lithium-rich manganese-based cathode material, including the following steps:

[0108] (1) Ni prepared by coprecipitation method 0.35 Mn 0.65 (OH)2 precursor, the preparation process is as described in Example 1.

[0109] (2) Take the Ni obtained in step (1) 0.35 Mn 0.65 The (OH)2 precursor and Li2CO3 powder were mixed evenly at a molar ratio of lithium to nickel and manganese of 1.3, and then sintered at 850°C for 15 hours in air atmosphere. After cooling to room temperature, a sintered product was obtained.

[0110] (3) The calcined product obtained in step (2) is mixed with 1% manganese hydroxide (i.e., the mass ratio of manganese hydroxide to calcined product is 1.0:100). The mixed sample is sintered at 800°C for 5 hours in air atmosphere. After cooling to room temperature, the lithium-rich manganese-based cathode material coated with manganese oxide can be obtained.

[0111] (4) Mix the product obtained in step (3) with 0.15% magnesium fluoride (i.e., the mass ratio of magnesium fluoride to calcined product is 0.15:100), and sinter the mixed sample at 600°C for 5 hours in an air atmosphere. After cooling to room temperature, the lithium-rich manganese-based cathode material coated with magnesium fluoride can be obtained.

[0112] Performance testing: Lithium-rich manganese-based cathode material, conductive carbon, and binder were mixed in a ratio of 90:5:5 to form a slurry. The slurry was then coated onto aluminum foil, dried, rolled, and cut into sheets. Finally, it was assembled with lithium foil to form a coin cell. The test range was 2.3V-4.55V.

[0113] Test results: As shown in Table 1, the sample of Example 5 has a discharge specific capacity of 235.8 mAh / g at a current density of 0.1C and an initial coulombic efficiency of up to 86.8%.

[0114] Example 6

[0115] This embodiment provides a method for preparing a lithium-rich manganese-based cathode material, including the following steps:

[0116] (1) Ni prepared by coprecipitation method 0.35 Mn 0.65 (OH)2 precursor, the preparation process is as described in Example 1.

[0117] (2) Take the Ni obtained in step (1) 0.35 Mn 0.65 The (OH)2 precursor and Li2CO3 powder were mixed evenly at a molar ratio of lithium to nickel and manganese of 1.3, and then sintered at 850°C for 15 hours in air atmosphere. After cooling to room temperature, a sintered product was obtained.

[0118] (3) The calcined product obtained in step (2) is mixed with 1% manganese hydroxyl oxide (i.e., the mass ratio of manganese hydroxyl oxide to calcined product is 1.0:100). The mixed sample is sintered at 800°C for 6 hours in an air atmosphere. After cooling to room temperature, the lithium-rich manganese-based cathode material coated with manganese oxide can be obtained.

[0119] (4) Mix the product obtained in step (3) with 0.30% zirconium oxide (i.e., the mass ratio of zirconium oxide to the sintered product is 0.3:100), and sinter the mixed sample at 750°C for 5 hours in an air atmosphere. After cooling to room temperature, the lithium-rich manganese-based cathode material coated with zirconium oxide can be obtained.

[0120] Performance testing: Lithium-rich manganese-based cathode material, conductive carbon, and binder were mixed in a ratio of 90:5:5 to form a slurry. The slurry was then coated onto aluminum foil, dried, rolled, and cut into sheets. Finally, it was assembled with lithium foil to form a coin cell. The test range was 2.3V-4.55V.

[0121] Test results: As shown in Table 1, the sample of Example 6 has a discharge specific capacity of 236.2 mAh / g at a current density of 0.1C and an initial coulombic efficiency of up to 87.0%.

[0122] Example 7

[0123] The only difference from Example 1 is that in step (4), alumina is replaced with an equal mass of strontium oxide.

[0124] Example 8

[0125] The only difference from Example 1 is that in step (4), aluminum oxide is replaced with an equal mass of titanium oxide.

[0126] Example 9

[0127] The only difference from Example 1 is that in step (4), alumina is replaced with 0.1% alumina (i.e., the mass ratio of alumina to the first-burn product is 0.1:100).

[0128] Example 10

[0129] The only difference from Example 1 is that in step (4), alumina is replaced with 0.5% alumina (i.e., the mass ratio of alumina to the first-burn product is 0.5:100).

[0130] Comparative Example 1

[0131] This comparative example provides a method for preparing a lithium-rich manganese-based cathode material, including the following steps:

[0132] (1) Ni prepared by coprecipitation method 0.35 Mn 0.65 (OH)2 precursor, the preparation process is as described in Example 1.

[0133] (2) Take the Ni obtained in step (1) 0.35 Mn 0.65 The (OH)2 precursor and Li2CO3 powder were mixed evenly at a molar ratio of lithium to nickel and manganese of 1.3. The mixture was then sintered at 850°C for 15 hours in air and cooled to room temperature to obtain the sintered product.

[0134] (3) The calcined product obtained in step (2) is mixed with 0.5% manganese oxide (i.e., the mass ratio of manganese oxide to calcined product is 0.5:100). The mixed sample is sintered at 800°C for 8 hours in an air atmosphere. After cooling to room temperature, the lithium-rich manganese-based cathode material coated with manganese oxide can be obtained.

[0135] Note: The only difference between Comparative Example 1 and Example 1 is that step (4) of the three-burning coating process is omitted.

[0136] Comparative Example 2

[0137] This comparative example provides a method for preparing a lithium-rich manganese-based cathode material, including the following steps:

[0138] (1) Ni prepared by coprecipitation method0.35 Mn 0.65 (OH)2 precursor, the preparation process is as described in Example 1.

[0139] (2) Take the Ni obtained in step (1) 0.35 Mn 0.65 The (OH)2 precursor and Li2CO3 powder were mixed evenly at a molar ratio of lithium to nickel and manganese of 1.3, and then sintered at 850°C for 15 hours in air atmosphere. After cooling to room temperature, a sintered product was obtained.

[0140] (3) The calcined product obtained in step (2) is mixed with 0.20% alumina (i.e., the mass ratio of alumina to calcined product is 0.2:100). The mixed sample is sintered at 600°C for 5 hours in air atmosphere. After cooling to room temperature, lithium-rich manganese-based cathode material coated with alumina can be obtained.

[0141] Note: The only difference between Comparative Example 2 and Example 1 is that the manganese compound-containing double-burning coating process in step (3) of Example 1 is not included.

[0142] Comparative Example 3

[0143] The only difference from Example 1 is that the manganese oxide in step (3) is replaced with an equal amount of nickel oxide.

[0144] Comparative Example 4

[0145] The only difference from Example 1 is that aluminum oxide is coated first, followed by manganese oxide.

[0146] Experimental Example 1

[0147] The performance of the lithium-rich manganese-based cathode materials prepared in the examples and comparative examples is shown in Tables 1 and 2.

[0148] Table 1. Results of first discharge specific capacity and coulombic efficiency tests of the cathode materials prepared in the examples and comparative examples.

[0149]

[0150] Table 2. Cyclic performance test results of the cathode materials prepared in the examples and comparative examples.

[0151]

[0152] As can be seen from Tables 1 and 2, the lithium-rich manganese-based cathode material prepared by the method of this embodiment has significantly better first discharge specific capacity and first coulombic efficiency than the comparative example, and its cycle performance after 100 cycles is also better.

[0153] It can be seen that in Comparative Example 2, the direct two-stage high-temperature coating, due to uneven matrix distribution, leads to phase transition, resulting in voltage drop and a significant decrease in cycle performance at high rates. At 1C, after 100 cycles, the capacity retention is 78%. Before the three-stage coating, the two-stage high-temperature coating of manganese oxide significantly improves the cycle performance at 1C, with a capacity retention of 87.8% after 100 cycles, a 10% improvement compared to the direct coating. This indicates that by high-temperature coating of manganese-containing compounds onto the surface of the lithium-rich manganese-based cathode material, making the surface manganese-rich, and controlling the distribution of the two phases, the matrix element distribution becomes more uniform, reducing the probability of phase transition during the two-stage high-temperature coating. Subsequent three-stage coating and sintering then improves capacity and maintains structural stability, thereby enhancing cycle performance at high rates.

[0154] Experimental Example 2

[0155] SEM images of lithium-rich manganese-based cathode materials were obtained from Test Example 1 and Comparative Examples 1-2, and the results are as follows: Figure 2 , Figure 3 and Figure 4 As shown.

[0156] As can be seen from the figure, the coatings of Example 1 and Comparative Example 1 are uniformly coated on the sample surface. In Comparative Example 2, no manganese source was added, resulting in partial agglomeration and the formation of obvious spinel phase, demonstrating the importance of the manganese source in the calcination coating.

[0157] Industrial applicability

[0158] This disclosure improves capacity and maintains structural stability by high-temperature coating of a first manganese-containing coating layer onto the surface of a lithium-rich manganese-based cathode material, followed by coating with elements such as Al, Zr, Sr, Ti, and Mg to form a second coating layer. This also enhances cycle life under high-rate conditions. The preparation method provided in this disclosure is simple, easy to implement, has low manufacturing cost, good reproducibility, and is suitable for large-scale industrial production.

Claims

1. A lithium-rich manganese-based cathode material, characterized in that, The invention includes a lithium-rich manganese-based substrate, wherein a first coating layer and a second coating layer are sequentially coated on the lithium-rich manganese-based substrate, and the first coating layer is located between the lithium-rich manganese-based substrate and the second coating layer. Wherein, the coating element in the first coating layer is Mn, and the coating element in the second coating layer is selected from at least one of Al, Zr, Sr, Ti and Mg; The first coating layer is a manganese oxide coating layer; The chemical formula of the lithium-rich manganese-based substrate is: xLi2MnO3·(1-x)LiTMO2, 0.4≤x≤0.8, where TM represents Ni and Mn; The mass ratio of the first coating layer to the lithium-rich manganese-based substrate is (0.1-2.0):100; The second coating layer is selected from at least one of oxides, phosphates and fluorides; the mass ratio of the second coating layer to the lithium-rich manganese-based substrate is (0.1-0.5):

100.

2. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, The coating element in the second coating layer is selected from at least one of Al and Zr.

3. A method for preparing the lithium-rich manganese-based cathode material according to any one of claims 1-2, characterized in that, include: The first coating layer and the second coating layer are sequentially formed on the lithium-rich manganese-based substrate.

4. The preparation method according to claim 3, characterized in that, A lithium-rich manganese-based substrate is mixed with a first coating material and sintered to obtain an intermediate product. The intermediate product is then mixed with a second coating material and sintered. The first coating material is a manganese source, and the second coating material contains the coating elements found in the second coating layer.

5. The preparation method according to claim 4, characterized in that, The mass ratio of the first coating material to the lithium-rich manganese-based substrate is (0.1-2.0):

100.

6. The preparation method according to claim 5, characterized in that, The first coating material is selected from at least one of manganese oxides, manganese hydroxides and manganese hydroxy oxides.

7. The preparation method according to claim 4, characterized in that, The sintering temperature of the lithium-rich manganese-based substrate and the first coating material is 600℃-900℃, and the sintering time is 5h-12h.

8. The preparation method according to claim 7, characterized in that, After the lithium-rich manganese-based substrate and the first coating material are sintered, the intermediate product is obtained by cooling to room temperature.

9. The preparation method according to claim 4, characterized in that, The second coating material is selected from at least one of oxides, phosphates and fluorides.

10. The preparation method according to claim 9, characterized in that, The mass ratio of the second coating material to the lithium-rich manganese-based substrate is (0.1-0.5):

100.

11. The preparation method according to claim 4, characterized in that, The intermediate product and the second coating material are sintered at a temperature of 600℃-800℃ for 5h-8h.

12. The preparation method according to claim 11, characterized in that, After the intermediate product and the second coating material are sintered, the mixture is cooled to room temperature.

13. The preparation method according to claim 4, characterized in that, The preparation process of the lithium-rich manganese-based substrate includes: mixing and sintering a hydroxide precursor and a lithium salt, wherein the hydroxide precursor contains manganese and nickel.

14. The preparation method according to claim 13, characterized in that, The sintering temperature of the hydroxide precursor and the lithium salt is 750℃-950℃, and the sintering time is 8h-15h.

15. The preparation method according to claim 14, characterized in that, By controlling the amounts of the hydroxide precursor and the lithium salt, the molar ratio of lithium element to the total amount of metal element in the hydroxide precursor is (1.1-1.6):

1.

16. The preparation method according to claim 13, characterized in that, The chemical formula of the hydroxide precursor is Ni y Mn 1-y (OH)2, where y = 0.2-0.

6.

17. The preparation method according to claim 16, characterized in that, The hydroxide precursor was prepared by a co-precipitation method.

18. The preparation method according to claim 13, characterized in that, The hydroxide precursor and the lithium salt were sintered under an oxygen-containing atmosphere, and then cooled to room temperature after sintering.

19. A positive electrode plate, characterized in that, Includes the lithium-rich manganese-based cathode material according to any one of claims 1-2 or the lithium-rich manganese-based cathode material prepared by the preparation method according to any one of claims 3-18.

20. A lithium battery, characterized in that, Includes the positive electrode sheet as described in claim 19.

21. An electrical appliance, characterized in that, Including the lithium battery described in claim 20.

Images