A lithium-rich manganese-based material and a method for preparing the same

Abstract

The application relates to the technical field of secondary battery positive electrode materials, in particular to a lithium-rich manganese-based material and a preparation method thereof. x (Ni a Mn b Te c M d ) 2‑x O2, wherein M is at least one selected from Nb and Ta, 1.1<=x<=1.16, 0.3<=a / (a+b)<=0.4, a+b+c+d=1.0, 0.0002<=c<=0.002, 0.0002<=d<=0.001, and 0.5<=c / d<=2.0; the lithium-rich manganese-based material is a polymorphic layered structure. By introducing Te elements and M elements and controlling the addition amount of the two, the specific surface area of the lithium-rich manganese-based material is reduced, and the lithium-rich manganese-based material has high capacity and rate performance and good structural stability.

Description

Technical Field

[0001] This application relates to the field of secondary battery cathode materials technology, and in particular to a lithium-rich manganese-based material and its preparation method. Background Technology

[0002] Compared to lithium iron phosphate, lithium manganese oxide, or ternary cathode materials, lithium-rich manganese-based materials offer higher energy density, greater safety, and lower economic costs, making them a potential next-generation cathode material with outstanding overall performance. However, due to their two-phase cross-linked structure of Li2MnO3 and LiTMO2 (TM selected from Ni, Co, or Mn), with the Li2MnO3 phase exhibiting lower ionic and electronic conductivity, the overall rate performance of lithium-rich manganese-based materials is lower than that of ternary cathode materials.

[0003] Currently, research institutions and companies mainly use carbonate or hydroxide precursors to prepare lithium-rich manganese-based materials. Cathode materials prepared using carbonate precursors have smaller primary particle sizes and higher surface porosity, resulting in shorter lithium-ion transport distances within individual primary particles, which is beneficial for improving rate performance. However, during the preparation process, the decomposition of the carbonate precursor generates a large amount of CO2, leading to high porosity in the cathode material. This results in more severe side reactions at the cathode interface during battery operation. The porosity of cathode materials can be defined by their specific surface area; cathode materials prepared using carbonate precursors typically have a specific surface area higher than 3 m². 2 / g, far exceeding the specific surface area of ​​existing industrialized ternary cathode materials (typically 0.5-0.8m²). 2 The aforementioned lithium-rich manganese-based material ( / g) exhibits high surface porosity, which will lead to severe side reactions with the electrolyte during battery use. Increasing the sintering temperature can reduce its porosity to some extent, lowering its specific surface area to 2-3 m². 2 / g, but because the primary particles of the cathode material prepared from the carbonate precursor do not have orientation, the primary particles are randomly squeezed and piled up. Therefore, when the sintering temperature is increased, that is, the pores between the primary particles are reduced, the lithium-ion transport channels of some primary particles will be blocked by other primary particles around them, resulting in battery capacity loss.

[0004] Lithium-rich manganese-based materials prepared using hydroxide precursors typically have large primary particle sizes, resulting in longer lithium-ion transport distances and consequently affecting the capacity and rate performance of the cathode material. One approach to address this issue is to adjust the synthesis parameters of the precursor to reduce the size of the primary particles. However, cathode materials obtained through this method still exhibit problems similar to those found in cathodes prepared using carbonate matrices, such as relatively loose primary particles and high specific surface area. Summary of the Invention

[0005] This application discloses a lithium-rich manganese-based material and its preparation method to solve the problem that existing lithium-rich manganese-based materials cannot simultaneously achieve high rate performance, high capacity and low specific surface area.

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] Firstly, this application provides a lithium-rich manganese-based material, the chemical formula of which is Li. x (Ni a Mn b Te c M d ) 2-x O2, wherein M is selected from at least one of Nb and Ta, 1.1≤x≤1.16, 0.3≤a / (a+b)≤0.4, a+b+c+d=1.0, 0.0002≤c≤0.002, 0.0002≤d≤0.001, and 0.5≤c / d≤2.0; the lithium-rich manganese-based material has a polycrystalline layered structure.

[0008] Furthermore, the specific surface area of ​​lithium-rich manganese-based materials is 0.5-1.0 m². 2 / g, surface porosity P≤5%.

[0009] Furthermore, the morphology of the lithium-rich manganese-based material is that of secondary particles, which are composed of agglomerations of multiple primary particles. The average thickness of the primary particles is 120-250 nm, the average length of the primary particles is 250-400 nm, and the average edge angle θ of the primary particles is... A The range is 115-150°.

[0010] Furthermore, the morphology of the lithium-rich manganese-based material is that of secondary particles, which are composed of agglomerations of multiple primary particles. The number of primary particles per unit area on the surface of the secondary particles is 35-55 per μm. 2 .

[0011] Furthermore, where 0.1 ≤ x ≤ 0.16; and / or, 0.33 ≤ a / (a+b) ≤ 0.4.

[0012] In a second aspect, this application provides a method for preparing a lithium-rich manganese-based material according to the first aspect. The method includes the following steps: mixing a nickel manganese hydroxide precursor, a lithium source, a first dopant, and a second dopant, and then subjecting the mixture to calcination at a temperature of 920-970°C to obtain the lithium-rich manganese-based material.

[0013] The first dopant is one or more of tellurium oxide and telluric acid, and the second dopant is selected from at least one of niobium oxide, niobium oxalate, niobium hydroxide, niobium carbide, tantalum oxide, tantalum carbide, and tantalum ethoxide.

[0014] Furthermore, the calcination treatment time is 10-15 hours.

[0015] Furthermore, it also includes the preparation of a nickel-manganese hydroxide precursor: a soluble nickel salt, a soluble manganese salt, a complexing agent, and a precipitant undergo a co-precipitation reaction in a solvent to obtain a first slurry. The pH value of the co-precipitation reaction is 9.0-11.50, and the D of the precipitate in the first slurry is... 50 The thickness is 2.5-10.5 μm; the first slurry is post-processed to obtain a nickel-manganese hydroxide precursor.

[0016] Further, post-processing includes aging, washing, centrifuging, and drying of the first slurry.

[0017] Thirdly, this application provides a lithium-ion battery comprising the lithium-rich manganese-based material of the first aspect, or the lithium-rich manganese-based material prepared by the preparation method of the second aspect.

[0018] The beneficial effects of adopting the technical solution of this application are as follows:

[0019] The lithium-rich manganese-based material provided in this application contains a Te element that accumulates at the grain boundaries of the cathode material. This reduces the size of the primary particles and increases their density, thereby decreasing the porosity of the lithium-rich manganese-based material and consequently reducing its specific surface area. A lower specific surface area means a smaller contact area between the cathode material and the electrolyte, effectively reducing the adverse effects of side reactions. Furthermore, this application strictly controls the amount of Te added. Insufficient Te will fail to effectively regulate the size of the primary particles, while excessive Te will inevitably hinder lithium-ion transport, leading to a decrease in the capacity and rate performance of the cathode material. It should be noted that the introduction of Te will sharpen the edges of the primary particles, i.e., reduce the edge angles, which is detrimental to improving the strength of the primary particles. Moreover, sharpened edges are prone to breakage during long-term cycling, causing fluctuations in structural stability. In this application, the introduction of element M (selected from at least one of Nb and Ta) in combination with element Te increases the edge angle and rounds the edges of the primary particles, thereby improving the structural strength of the primary particles and reducing the risk of structural stability fluctuations during long-term cycling. Furthermore, when 0.5 ≤ c / d ≤ 2.0, the amount of Te added is matched with the amount of M added to ensure that the lithium-rich manganese-based material possesses both a small specific surface area and high capacity and rate performance, as well as good structural stability. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the calculation method for the average edge angle of a primary particle in this application;

[0021] Figure 2 This is a SEM image of the lithium-rich manganese-based material in Example 1 of this application;

[0022] Figure 3 To use the Metis software for Figure 1 A schematic diagram of a single particle simulation and identification process;

[0023] Figure 4 This is a SEM image of the lithium-rich manganese-based material in Example 5 of this application;

[0024] Figure 5 Here is a SEM image of the lithium-rich manganese-based material in Comparative Example 1 of this application;

[0025] Figure 6 Here is a SEM image of the lithium-rich manganese-based material in Comparative Example 3 of this application;

[0026] Figure 7 Here is a SEM image of the lithium-rich manganese-based material in Comparative Example 8 of this application;

[0027] Figure 8 This is a SEM image of the lithium-rich manganese-based material in Comparative Example 13 of this application. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] The application scenarios described in this application are for the purpose of more clearly illustrating the technical solutions of this application, and do not constitute a limitation on the technical solutions provided in this application. Those skilled in the art will understand that with the emergence of new application scenarios, the technical solutions provided in this application are also applicable to similar technical problems. In the description of this application, unless otherwise stated, "multiple" means two or more.

[0030] This application provides a lithium-rich manganese-based material, the chemical formula of which is Li. x (Ni a Mn b Te c M d ) 2-xO2, wherein M is selected from at least one of Nb and Ta, 1.1≤x≤1.16, 0.3≤a / (a+b)≤0.4, a+b+c+d=1.0, 0.0002≤c≤0.002, 0.0002≤d≤0.001, and 0.5≤c / d≤2.0; the lithium-rich manganese-based material has a polycrystalline layered structure.

[0031] Where 1.1 ≤ x ≤ 1.16, and x can be any value between 1.1, 1.12, 1.14, 1.16, or 1.1-1.16, it can be understood that when the Li content is too high, the fluxing properties of lithium will cause excessive growth of primary particles, resulting in a small specific surface area of ​​the cathode material, decreased kinetic performance, and a significant reduction in capacity. Furthermore, excessively high lithium content will increase the valence state of the transition metal; the increased valence state of nickel leads to a decrease in the number of electrons it can provide, reducing the amount of lithium that can be delithiated from the cathode material and thus reducing capacity. Conversely, if the Li content is too low, a lithium-rich crystal structure cannot be formed. Therefore, when 1.1 ≤ x ≤ 1.16, the specific surface area and the amount of lithium that can be delithiated from the cathode material are within a suitable range, which helps to improve the capacity of the cathode material.

[0032] Where 0.3 ≤ a / (a+b) ≤ 0.4, and a / (a+b) can be 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, or any other value between 0.3 and 0.4. It is understandable that increasing the nickel content will increase the metal cost of the cathode material, while the decrease in the proportion of manganese-rich phase will also decrease the energy density of the cathode material. When 0.3 ≤ a / (a+b) ≤ 0.4, the nickel content is moderate, ensuring an appropriate proportion of lithium-rich phase, which can balance the manufacturing cost and energy density of the cathode material, achieving a balance between capacity and kinetic performance. Preferably, 0.33≤a / (a+b)≤0.4, that is, when the molar ratio of nickel to nickel-manganese is 0.33-0.4, compared with the molar ratio of nickel to nickel-manganese is 0.3-0.32, appropriately reducing the proportion of lithium-rich phase and increasing the proportion of ternary phase reduces the extent of anion participation in redox in the cathode material, improves structural stability and kinetic performance, while the capacity of the cathode material can remain basically unchanged.

[0033] Wherein, 0.5 ≤ c / d ≤ 2.0, and c / d can be any value between 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, or 0.5-2.0. It is understandable that excessive M will lead to a significant decrease in the capacity of the cathode material, while insufficient M will fail to optimize the edge morphology of the primary particles. The amount of Te added is positively correlated with the amount of M added. When the molar amount of M is 0.5-2 times the molar amount of Te, the lithium-rich manganese-based material in this application possesses both a smaller specific surface area, higher capacity and rate performance, and rounds the surface and edges of the primary particles, improving the structural strength of the primary particles and reducing the risk of structural degradation during long-term cycling, thereby improving the cycle stability of the lithium-rich manganese-based material.

[0034] In one embodiment of this application, the specific surface area of ​​the lithium-rich manganese-based material is 0.5-1.0 m². 2 / g, with a specific surface area of, for example, 0.5m². 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g or 0.5-1.0m 2 Any other value between / g. The lithium-rich manganese-based material has a small specific surface area, which can effectively reduce interfacial side reactions and improve the cycle stability of the battery.

[0035] In one embodiment of this application, the surface porosity P is ≤ 5%, and examples of surface porosity P include 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, etc. The low porosity of lithium-rich manganese-based materials helps to limit electrolyte penetration and prevent corrosion and degradation of the cathode material by the electrolyte.

[0036] In one embodiment of this application, the lithium-rich manganese-based material has the morphology of secondary particles, which are formed by the agglomeration of multiple primary particles.

[0037] Optionally, the average thickness of the primary particles is 120-250 nm; optionally, the average length of the primary particles is 250-400 nm. Understandably, the moderate size of the primary particles ensures rapid lithium-ion transport, thereby improving the capacity and rate performance of lithium-rich manganese-based materials.

[0038] It should be noted that the thickness of a primary particle refers to the dimension in the direction perpendicular to the length of the primary particle.

[0039] Optionally, the average edge angle θ of the primary particles A The range is 115-150°.

[0040] In one embodiment of this application, the number of primary particles per unit area on the secondary particle surface layer is 35-55 particles / μm. 2 This is to ensure that the primary particles in the secondary particles have a high close packing order.

[0041] Based on the same inventive concept, this application also provides a method for preparing lithium-rich manganese-based materials. The preparation method includes the following steps: mixing a nickel manganese hydroxide precursor, a lithium source, a first dopant, and a second dopant, and then subjecting the mixture to calcination at a temperature of 920-970°C to obtain lithium-rich manganese-based materials.

[0042] The first dopant is one or more of tellurium oxide and telluric acid.

[0043] The second dopant is selected from at least one of niobium oxide, niobium oxalate, niobium hydroxide, niobium carbide, tantalum oxide, tantalum carbide, and tantalum ethoxide.

[0044] In one embodiment of this application, the lithium source is a lithium salt such as lithium carbonate and / or lithium hydroxide.

[0045] The molar ratio of nickel manganese hydroxide precursor to lithium source is 1:1.25-1.36.

[0046] In one embodiment of this application, the calcination treatment time is 10-15 hours. After calcination, the material is allowed to cool naturally to room temperature and then sieved to obtain the lithium-rich manganese-based material of this application. It is understood that excessively high or low calcination temperatures will affect the average length and average width of the primary particles, as well as the specific surface area of ​​the cathode material.

[0047] Optionally, the calcination process is carried out in a box furnace or roller kiln, preferably with a heating rate of 2°C / min.

[0048] In one embodiment of this application, the preparation of a nickel-manganese hydroxide precursor is further included: a soluble nickel salt, a soluble manganese salt, a complexing agent, and a precipitant undergo a co-precipitation reaction in a solvent to obtain a first slurry, wherein the pH value of the co-precipitation reaction is 9.0-11.50, and the D of the precipitate in the first slurry is... 50 The thickness is 2.5-10.5 μm; the first slurry is post-processed to obtain a nickel-manganese hydroxide precursor.

[0049] Examples of pH values ​​for the coprecipitation reaction include 9.0, 9.5, 10.0, 10.5, 11.0, 11.50, or any other value between 9.0 and 11.50. Examples of D50 values ​​for the precipitate in the first slurry include 2.5 μm, 3.0 μm, 6.5 μm, 7.0 μm, 9.5 μm, 10.0 μm, 10.5 μm, or any other value between 2.5 and 10.5 μm.

[0050] In one embodiment of this application, the temperature of the coprecipitation reaction is 50–60°C. Optionally, the coprecipitation reaction is carried out under stirring at a speed of 400–800 rpm.

[0051] Optionally, the coprecipitation reaction is carried out in an inert gas atmosphere, wherein the inert gas is selected from nitrogen, argon, and helium.

[0052] In one embodiment of this application, the post-processing includes aging, washing, centrifuging, and drying the first slurry.

[0053] Optionally, the soluble nickel salt includes at least one of nickel sulfate, nickel nitrate, nickel chloride, or nickel acetate. Optionally, the soluble manganese salt includes at least one of manganese sulfate, manganese nitrate, manganese chloride, or manganese acetate.

[0054] The molar ratio of nickel ions in the soluble nickel salt to manganese ions in the soluble manganese salt is a:b, and the sum of their molar amounts is 1.5-2.5 mol / L.

[0055] In one embodiment of this application, the complexing agent includes at least one of ammonia, ammonium bisulfate, or ammonium sulfate. The concentration of the complexing agent is 10-35 wt%.

[0056] In one embodiment of this application, the precipitant may be a sodium hydroxide solution or lithium hydroxide. The concentration of the precipitant is 6.0-12.0 mol / L.

[0057] Based on the same inventive concept, this application also provides a lithium-ion battery, wherein the positive electrode of the lithium-ion battery comprises the lithium-rich manganese-based material in various possible embodiments of this application, or the positive electrode of the lithium-ion battery comprises the lithium-rich manganese-based material prepared by the preparation method in various possible embodiments of this application.

[0058] Because it includes lithium-rich manganese-based materials as described in this application or lithium-rich manganese-based materials prepared using the methods described in this application, this lithium-ion battery possesses high capacity and rate performance, as well as good structural stability, which will not be elaborated further here.

[0059] The lithium-rich manganese-based materials and their preparation methods in this application will be further described in detail below with reference to specific embodiments and comparative examples.

[0060] Example 1

[0061] This embodiment describes a lithium-rich manganese-based material, and the preparation method of this lithium-rich manganese-based material includes the following steps:

[0062] 1) Prepare a mixed metal salt solution of nickel sulfate and manganese sulfate with a total molar concentration of 2.5 mol / L, wherein the molar ratio of nickel ions in nickel sulfate to manganese ions in manganese sulfate is 35:65; prepare a 10 mol / L sodium hydroxide solution and a 10 wt% ammonia solution.

[0063] 2) Fill a 50L reactor with clean water, and set the stirring speed to 800 rpm and the temperature to 55℃. Then, introduce nitrogen gas into the reactor and exhaust it for 2 hours. After that, introduce a mixed metal salt solution, sodium hydroxide solution, and ammonia solution into the reactor to induce a co-precipitation reaction and obtain the first slurry. The flow rates of the above solutions are 2L / min, 0.5L / min, and 0.05L / min, respectively. The pH of the reaction system is 9.8. The D of the precipitate in the first slurry is... 50 =10.0μm, stop feeding and collect the first slurry in the reactor;

[0064] 3) The first slurry is subjected to aging, washing, centrifugation, and drying to obtain the hydroxide precursor Ni. 0.35 Mn 0.65 (OH)2;

[0065] 4) The precursor, lithium carbonate, TeO2, and Ta2O5 obtained in step 3) are mixed evenly and sintered in a box furnace at a heating rate of 2℃ / min, a sintering temperature of 950℃, and a holding time of 12h. Then, the mixture is allowed to cool naturally to room temperature and sieved to obtain a lithium-rich manganese-based material. The molar ratio of the precursor to lithium carbonate is 1:1.3, and the molar amounts of nickel ions and manganese ions: molar amounts of Te ions: molar amounts of Ta ions = 0.9985:0.001:0.0005.

[0066] Examples 2-14 and Comparative Examples 1-14

[0067] Examples 2-14 and Comparative Examples 1-14 are lithium-rich manganese-based materials. The specific steps can be referred to Example 1. In Examples 1-12, the first dopant and the second dopant are both oxides. In Example 13, the first dopant is telluric acid and the second dopant is tantalum carbide. In Example 14, the first dopant is telluric acid and the second dopant is tantalum ethoxide. Other differences are listed in Table 1.

[0068] Table 1

[0069]

[0070] The average thickness, average length, and average edge angle of the primary particles in the cathode materials of the above embodiments and comparative examples, as well as the specific surface area, surface porosity, and number of primary particles per unit area of ​​the secondary particle surface layer of the cathode materials were measured. The test results are shown in Table 2 below.

[0071] The measured molar ratio of nickel, manganese, and lithium was determined by ICP-OES.

[0072] The determination of surface porosity includes the following steps:

[0073] The cathode material was imaged using a scanning electron microscope (SEM) to obtain an SEM image. Then, ImageJ software was used to quantitatively analyze the grayscale of the surface of a single secondary particle of the cathode material. Specifically, the RGB threshold was first set to 90, and the area ratio of the region with RGB range 0-90 in the selected area image of a single secondary particle was obtained, denoted as X1. Similarly, the area ratio of the region with RGB range 0-252 in the same selected area image of the same single secondary particle was denoted as X2. The porosity of the material cross section was then obtained as X1 / X2*100%. Ten sets of data were tested, and the average value was taken to obtain the surface porosity of the cathode material.

[0074] The process involved using SEM (Scanning Electron Microscopy) to image the cathode material, observing its morphology, and determining the average thickness and length of at least 100 random primary particles in a selected region of the SEM image using Nano Measure software. The specific surface area was determined using the nitrogen adsorption BET method, and the particle size of the primary particles was measured using a laser particle size analyzer. 50 This represents the particle size of the cathode material, measured from the smallest particle size to 50% of the total volume, in a volume-based particle size distribution.

[0075] The average edge angle θ of a primary particle A Measurement method: Observe the SEM images of the cathode materials obtained from all examples and comparative examples, select particles with complete and uncovered side profiles, and measure their edge angle θ. Perform 50 sets of tests and take the average value. Figure 1 This is a schematic diagram illustrating the calculation method for the average edge angle of a primary particle in this application, with reference to... Figure 1 Along the length of the primary particle, with one end uncovered, the angles of the two edge angles on either side of the end were measured. The smaller angle value was selected as the edge angle θ of a single primary particle. Fifty sets of edge angle θ data were measured, and the average value was recorded as the average edge angle θ of the primary particle. A .

[0076] The method for determining the number of primary particles per unit area on the surface of secondary particles is as follows: The cathode material is imaged using SEM to obtain an SEM image at a magnification of 30,000x. The primary particles are simulated and identified using the Euler-Metis image segmentation software, with selected areas >4μm. 2To ensure that the unidentified area accounts for less than 10%, calculate the number of primary particles in the selected simulation area, and then divide it by the area of ​​the simulation area to obtain the number of primary particles per unit area, Num. Use the above method to count the number of primary particles per unit area, Num, of at least 10 samples, and calculate the average value to obtain the number of primary particles per unit area on the surface of secondary particles.

[0077] The surface layer refers to the region extending 50 nanometers radially from the surface of the secondary particle towards its center.

[0078] Table 2

[0079]

[0080] The positive electrode materials from the above embodiments and comparative examples were assembled into liquid coin cell half-cells. The assembly method was as follows: the obtained positive electrode material, conductive agent Super-P, and binder polyvinylidene fluoride (PVDF) were added to N-methylpyrrolidone (NMP) solvent in a ratio of 94:3:3 and mixed evenly to obtain a slurry. The obtained slurry was then coated, dried, punched, and rolled to obtain a positive electrode sheet. The stainless steel shell, positive electrode sheet, PP separator, and lithium sheet of the coin cell were stacked in sequence, a certain amount of electrolyte was added, and the cells were sealed and allowed to stand to obtain a liquid coin cell half-cell. The performance of the above liquid coin cell half-cell was tested. The specific test items and test methods are as follows:

[0081] 1. 0.2C discharge capacity

[0082] Test method: After the assembled liquid coin cell half battery has been left to stand for 5 hours, it is charged at a constant current of 0.2C to 4.55V, then charged at a constant voltage of 4.55V until the cutoff current is equal to 0.02C. After standing for 5 minutes, it is discharged at a constant current of 0.2C to 2.5V. The resulting discharge capacity is the 0.2C discharge capacity.

[0083] 2. First Coulomb Efficiency

[0084] Test method: After the assembled liquid coin cell half-cell has been left to stand for 5 hours, it is charged at a constant current of 0.2C to 4.55V, then charged at a constant voltage of 4.55V until the cutoff current is equal to 0.02C. After standing for 5 minutes, it is discharged at a constant current of 0.2C to 2.5V. The resulting discharge capacity / charge capacity is the initial coulombic efficiency.

[0085] 3. Capacity retention rate after 300 cycles at 1.0C

[0086] Test method: After testing the first discharge capacity of the liquid coin cell, charge it at a constant current of 1.0C to 4.55V, then charge it at a constant voltage of 4.55V until the cutoff current is equal to 0.02C. After resting for 5 minutes, discharge it at a constant current of 1.0C to 2.5V. Repeat this process 300 times, that is, charge and discharge at a rate of 1.0C for 300 cycles. The discharge capacity of the 300th cycle / the discharge capacity of the 1st cycle is the capacity retention rate of the 1.0C cycle for 300 cycles.

[0087] The specific test results are shown in Table 3 below.

[0088] Table 3

[0089]

[0090]

[0091] Figure 2 This is a SEM image of the lithium-rich manganese-based material in Example 1 of this application. Figure 3 To use the Metis software for Figure 1 A schematic diagram of a particle simulation and identification process is shown below. Figure 2 and Figure 3 In Example 1, the primary particles of the lithium-rich manganese-based material have an average thickness of 165 nm and an average length of 316 nm. The number of primary particles per unit area on the surface of the secondary particles is 42 particles / μm. 2 .

[0092] Figure 4 Here is a SEM image of the lithium-rich manganese-based material in Example 5 of this application, with reference to... Figure 5 Based on the data in Tables 1 to 3, it can be seen that, compared with Example 1, the proportion of the molar amount of lithium ions in the sum of the molar amounts of nickel, manganese, and lithium ions is increased in Example 5, and the fluxing properties of lithium lead to a slight increase in the primary particle size.

[0093] Figure 5 Here is a SEM image of the lithium-rich manganese-based material in Comparative Example 1 of this application, with reference to... Figure 5 Based on the data in Tables 1 to 3, it can be seen that, compared with Example 1, Comparative Example 1 did not add the first dopant and the second dopant, resulting in excessively large primary particles and excessively high surface porosity, which led to a decrease in the overall performance of the prepared battery.

[0094] Figure 6 Here is a SEM image of the lithium-rich manganese-based material in Comparative Example 3 of this application, with reference to... Figure 6 Based on the data in Tables 1 to 3, it can be seen that, compared with Example 1, Comparative Example 3 did not add a second dopant, which resulted in a smaller average edge angle of the primary particles, excessively sharp edges of the primary particles, and reduced structural strength at the edges, thereby leading to a decrease in the overall performance of the prepared battery.

[0095] Figure 7 Here is a SEM image of the lithium-rich manganese-based material in Comparative Example 8 of this application, with reference to... Figure 7 Based on the data in Tables 1 to 3, it can be seen that, compared with Example 1, the amount of the second dopant added in Comparative Example 8 is too low compared with the amount of the first dopant. This results in a smaller edge angle of the primary particles, excessively sharp edges of the primary particles, and reduced structural strength at the edges, thereby leading to a decrease in the overall performance of the prepared battery.

[0096] Figure 8 Here is a SEM image of the lithium-rich manganese-based material in Comparative Example 13 of this application, with reference to... Figure 8 Based on the data in Tables 1 to 3, it can be seen that, compared with Example 1, the sintering temperature of Comparative Example 13 was too low, resulting in the primary particle size being too fine, which led to a decrease in the stability of the secondary particle structure and a decrease in surface stability.

[0097] According to the data from Examples 1, 11, and 12, the D of the precipitate in the first slurry 50 Adjustments within a limited range have little impact on the performance of the cathode material. With the effective combination of the first and second dopants, it can be guaranteed that the material meets the preferred physicochemical properties and excellent electrochemical performance.

[0098] Referring to the data from Examples 1 and Comparative Examples 11 and 12, it can be seen that when the molar ratio of precursor to lithium source is within the range of 1:1.25-1.36, the cathode material exhibits good overall performance. In Comparative Example 11, the lithium source ratio is too low, which may lead to the formation of an inert rock salt phase in the cathode material due to insufficient lithium in certain areas, resulting in a decrease in capacity and impaired rate performance. In Comparative Example 12, the lithium source ratio is too high, resulting in excessively large primary particle size, which also leads to a decrease in kinetic performance, thereby limiting the capacity of the cathode material and deteriorating its cycle performance.

[0099] The above are merely specific embodiments of this application, but the scope of protection of this application 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 this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A lithium-rich manganese-based material, characterized in that, The chemical formula of the lithium-rich manganese-based material is Li x (Ni a Mn b Te c M d ) 2- x O2, wherein M is selected from at least one of Nb and Ta, 1.1≤x≤1.16, 0.3≤a / (a+b)≤0.4, a+b+c+d=1.0, 0.0002≤c≤0.002, 0.0002≤d≤0.001, and 0.5≤c / d≤2.0; The lithium-rich manganese-based material has a polycrystalline layered structure.

2. The lithium-rich manganese-based material according to claim 1, characterized in that, The specific surface area of ​​the lithium-rich manganese-based material is 0.5-1.0 m². 2 / g, surface porosity P≤5%.

3. The lithium-rich manganese-based material according to claim 2, characterized in that, The lithium-rich manganese-based material has a secondary particle morphology, which is composed of multiple primary particles aggregated together. The primary particles have an average thickness of 120-250 nm, an average length of 250-400 nm, and an average edge angle θ. A The range is 115-150°.

4. The lithium-rich manganese-based material according to claim 2, characterized in that, The lithium-rich manganese-based material has a secondary particle morphology, which is composed of agglomerations of multiple primary particles. The number of primary particles per unit area on the surface of the secondary particles is 35-55 per μm. 2 .

5. The lithium-rich manganese-based material according to claim 1, characterized in that, in, 1.12≤x≤1.16; and / or, 0.33≤a / (a+b)≤0.

4.

6. A method for preparing a lithium-rich manganese-based material as described in any one of claims 1-5, characterized in that, Includes the following steps: The nickel-manganese hydroxide precursor, lithium source, first dopant, and second dopant are mixed and then calcined at a temperature of 920-970℃ to obtain the lithium-rich manganese-based material. Wherein, the first dopant is one or more of tellurium oxide and telluric acid, and the second dopant is selected from at least one of niobium oxide, niobium oxalate, niobium hydroxide, niobium carbide, tantalum oxide, tantalum carbide, and tantalum ethoxide.

7. The preparation method according to claim 6, characterized in that, The sintering process takes 10-15 hours.

8. The preparation method according to claim 6 or 7, characterized in that, It also includes the preparation of the nickel-manganese hydroxide precursor: A first slurry is obtained by co-precipitating a soluble nickel salt, a soluble manganese salt, a complexing agent, and a precipitating agent in a solvent. The pH value of the co-precipitation reaction is 9.0-11.

50. The D of the precipitate in the first slurry is... 50 Its thickness ranges from 2.5 to 10.5 μm. The first slurry is post-processed to obtain the nickel-manganese hydroxide precursor.

9. The preparation method according to claim 8, characterized in that, The post-processing includes aging, washing, centrifuging, and drying the first slurry.

10. A lithium-ion battery, characterized in that, Includes the lithium-rich manganese-based material as described in any one of claims 1-5, or includes the lithium-rich manganese-based material prepared by the preparation method described in any one of claims 6-9.

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