A lithium-rich manganese-based precursor, and a preparation method and application thereof

Abstract

The application discloses a lithium-rich manganese-based precursor and a preparation method and application thereof. The lithium-rich manganese-based precursor is an element-doped nickel-cobalt-manganese hydroxide, and the doped elements in the lithium-rich manganese-based precursor include Zr and W. The application co-dopes the nickel-cobalt-manganese hydroxide with zirconium and tungsten, which is helpful to improve the electrochemical performance of the material, especially the cycle performance and the initial efficiency.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to a lithium-rich manganese-based precursor, its preparation method, and its application. Background Technology

[0002] Lithium-rich manganese-based cathode materials have attracted widespread attention due to their high energy density and high discharge capacity. However, these materials exhibit low conductivity, leading to increased contact resistance between the electrode and electrolyte during high-rate charge-discharge cycles. Combined with concentration polarization and side reactions, these materials demonstrate poor performance in practical power battery applications under high-rate charge-discharge conditions. They suffer from low initial charge-discharge coulombic efficiency and poor cycle performance, thus placing them far from practical application.

[0003] CN108557905A discloses a lithium-rich manganese-based material precursor, which is a sheet-like lithium-rich manganese-based carbonate precursor. The preparation process includes: simultaneously metering and pumping a mixed salt solution, a precipitant, and a complexing agent into a reactor at a rate of 0.12 L / h-0.9 L / h; controlling the reaction temperature at 35℃-65℃, the pH value at 7.5-8.5, and the stirring speed at 400 rpm / min-1000 rpm / min; aging for 5h-20h after the reaction; separating, washing, and drying the precipitate to obtain the sheet-like lithium-rich manganese-based carbonate precursor. However, this method has difficulty controlling the particle size of the lithium-rich manganese-based material precursor during preparation, easily resulting in fine particles, which in turn affects its electrochemical performance.

[0004] CN104466162B discloses a method for preparing a gradient lithium-rich manganese-based precursor and a gradient lithium-rich manganese-based cathode material. The method includes: preparing mixed solutions A, B, and C with different manganese ion contents, and sequentially adding them to a first reactor, a second reactor, and a third reactor for reaction; the first reactor, the second reactor, and the third reactor are connected in series for cyclic reaction to obtain the gradient lithium-rich manganese-based precursor. However, this method has a complex preparation process and is difficult to scale up for industrial production.

[0005] Therefore, providing a simple method for preparing lithium-rich manganese-based cathode materials that exhibits high initial efficiency and excellent cycle performance is a technical problem that urgently needs to be solved. Summary of the Invention

[0006] To address the aforementioned problems in the existing technology, the present invention aims to provide a lithium-rich manganese-based precursor, its preparation method, and its applications. By doping the lithium-rich manganese-based precursor with specific elements, the present invention enables the lithium-rich manganese-based cathode material prepared using this precursor to exhibit high initial efficiency, excellent cycle performance, and good resistance to voltage decay.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a lithium-rich manganese-based precursor, wherein the lithium-rich manganese-based precursor is an element-doped nickel-cobalt-manganese hydroxide, and the doping elements in the lithium-rich manganese-based precursor include Zr and W.

[0009] This invention utilizes zirconium and tungsten to co-dope nickel-cobalt-manganese hydroxide, which helps improve the electrochemical performance of the material, especially its cycle performance and first-efficiency performance.

[0010] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0011] Preferably, in the lithium-rich manganese-based precursor, the molar ratio of manganese, nickel and cobalt is x:y:z, where x>0.5, 0.4>y>0.01, 0.4>z>0.01, and x+y+z<1.

[0012] Preferably, based on the total mass of the lithium-rich manganese-based precursor, the Zr doping amount is 1000ppm-3000ppm, such as 1000ppm, 1200ppm, 1400ppm, 1500ppm, 1750ppm, 1800ppm, 2000ppm, 2100ppm, 2200ppm, 2300ppm, 2400ppm, 2500ppm, 2600ppm, 2700ppm, 2800ppm, 2900ppm, or 3000ppm.

[0013] Preferably, based on the total mass of the lithium-rich manganese-based precursor, the doping amount of W element is 700ppm-1500ppm, such as 700ppm, 800ppm, 900ppm, 1000ppm, 1100ppm, 1200ppm, 1300ppm, 1400ppm or 1500ppm.

[0014] Preferably, the molar ratio of Zr to W is (1.5-3):1, such as 1.5:1, 1.7:1, 1.8:1, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1 or 3:1, etc.

[0015] By limiting the doping amounts of Zr and W, as well as the molar ratio of Zr to W, the composition and structure of lithium-rich manganese-based precursors can be further controlled and optimized, thereby improving the electrochemical performance of lithium-rich manganese-based cathode materials prepared using them.

[0016] Preferably, the doping element also includes Cr.

[0017] Preferably, the ratio of the total molar amount of Zr and W to the molar amount of Cr is (1.5-4):1, for example, 1.5:1, 1.7:1, 2:1, 2.3:1, 2.5:1, 2.8:1, 3:1, 3.3:1, 3.6:1 or 4:1, etc.

[0018] By further doping a certain amount of chromium on the basis of co-doping with zirconium and tungsten, a synergistic effect can be achieved, which can further improve the electrochemical performance of the lithium-rich manganese-based cathode material prepared by using it.

[0019] Preferably, the particle size of the lithium-rich manganese-based precursor is 5μm-10μm, such as 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm or 10μm.

[0020] In a second aspect, the present invention provides a method for preparing a lithium-rich manganese-based precursor as described in the first aspect, the method comprising the following steps:

[0021] Prepare a nickel-cobalt-manganese mixed solution, a base solution, a precipitant solution, a complexing agent solution, a zirconium source solution, and a tungsten source solution;

[0022] The nickel-cobalt-manganese mixed solution, precipitant solution, and complexing agent solution are added to a reaction vessel containing a base liquid. The temperature and pH of the reaction system are controlled to preset values. After the coprecipitation reaction begins, zirconium source solution and tungsten source solution are added, and the reaction continues to obtain a lithium-rich manganese-based precursor.

[0023] In the method of the present invention, the preparation order of the nickel-cobalt-manganese mixed solution, the base solution, the precipitant solution, the complexing agent solution, the zirconium source solution, and the tungsten source solution is not important; they can be prepared simultaneously or sequentially. The present invention does not impose any specific limitations.

[0024] In the method of this invention, when the temperature and pH are controlled to preset values, a co-precipitation reaction occurs to form nickel-cobalt-manganese hydroxide. After the co-precipitation reaction begins, a zirconium source solution and a tungsten source solution are added to achieve co-doping of zirconium and tungsten, thereby obtaining a high-performance lithium-rich manganese-based precursor. Moreover, this method is simple and suitable for industrial production.

[0025] It should be noted that in this invention, the zirconium source solution and tungsten source solution should be added after the temperature and pH have reached the preset values, that is, after the co-precipitation reaction has started. If these two dispersions are added to the reaction vessel containing the base liquid at the same stage as the nickel-cobalt-manganese mixed solution, precipitant solution and complexing agent solution, and then the temperature and pH are controlled, the reaction product will be a different precursor material than desired.

[0026] In this invention, the nickel-cobalt-manganese solution refers to a solution containing nickel, cobalt, and manganese elements, which can be prepared by dissolving nickel salts, cobalt salts, and manganese salts in water.

[0027] Preferably, the base solution is prepared by adding water to the reaction vessel and then adding ammonia to bring the pH of the base solution to 9.5-11.5, such as 9.5, 9.8, 10, 10.3, 10.5, 10.7, 11, 11.2 or 11.5.

[0028] Preferably, the precipitant solution is a NaOH or KOH solution with a mass concentration of 25%-35% (e.g., 25%, 27%, 28%, 30%, 31%, 32%, 33%, or 35%).

[0029] Preferably, the complexing agent solution is an ammonia solution with a mass concentration of 15%-25% (e.g., 15%, 16%, 18%, 19%, 20%, 22%, 23%, or 25%).

[0030] In the method of the present invention, the precipitant solution and the complexing agent solution can be added to the reaction vessel separately, or they can be mixed and then added to the reaction vessel.

[0031] Preferably, the addition rate of the nickel-cobalt-manganese mixed solution is 10L / h-100L / h, such as 10L / h, 20L / h, 30L / h, 40L / h, 50L / h, 60L / h, 70L / h, 80L / h, 90L / h, or 100L / h.

[0032] Preferably, the zirconium source in the zirconium source solution includes at least one of Zr(SO4)2, ... and ...;

[0033] Preferably, the concentration of the zirconium source solution is 0.1 g / L-3 g / L, such as 0.1 g / L, 0.3 g / L, 0.5 g / L, 0.7 g / L, 0.8 g / L, 1 g / L, 1.2 g / L, 1.5 g / L, 2 g / L, 2.3 g / L, 2.6 g / L, or 3 g / L.

[0034] Preferably, the flow rate of the zirconium source solution is 0.3L / h-3L / h, such as 0.3L / h, 0.4L / h, 0.5L / h, 0.6L / h, 0.8L / h, 1L / h, 1.2L / h, 1.5L / h, 1.8L / h, 2L / h, 2.5L / h, or 3L / h.

[0035] Preferably, the tungsten source in the tungsten source solution includes at least one of ammonium tungstate and Na2WO4.

[0036] Preferably, the concentration of the tungsten source solution is 0.1 g / L-3 g / L, such as 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.5 g / L, 0.7 g / L, 1 g / L, 1.3 g / L, 1.6 g / L, 1.8 g / L, 2 g / L, 2.2 g / L, 2.5 g / L, 2.8 g / L, or 3 g / L.

[0037] Preferably, the flow rate of the tungsten source solution is 0.3L / h-3L / h, such as 0.3L / h, 0.4L / h, 0.5L / h, 0.6L / h, 0.8L / h, 1L / h, 1.2L / h, 1.5L / h, 1.8L / h, 2L / h, 2.5L / h, or 3L / h.

[0038] Preferably, the preparation method further includes: preparing a chromium source solution, and adding the chromium source solution and the nickel-cobalt-manganese mixed solution in parallel into a container to perform chromium doping.

[0039] Preferably, the preset temperature value is 40℃-65℃, such as 40℃, 43℃, 45℃, 46℃, 48℃, 50℃, 52℃, 55℃, 58℃, 60℃, 63℃ or 65℃, etc.; the preset pH value is 9.5-11.5, such as 9.5, 9.8, 10, 10.3, 10.5, 10.7, 11, 11.2 or 11.5, etc.

[0040] Preferably, after controlling the temperature and pH of the reaction system to preset values, stirring is started, and the zirconium source solution and tungsten source solution are added under stirring conditions. The stirring speed is 200 r / min-400 r / min (e.g., 200 r / min, 250 r / min, 300 r / min, 350 r / min, or 400 r / min, etc.). By stirring during the addition and reaction processes, the dispersion uniformity of the reaction can be improved, which is beneficial to improving product performance.

[0041] Thirdly, the present invention provides a lithium-rich manganese-based cathode material, which is prepared using the lithium-rich manganese-based precursor as described in the first aspect, and the lithium-rich manganese-based cathode material is doped with Zr and W.

[0042] Preferably, the lithium-rich manganese-based cathode material is also doped with Cr.

[0043] Preferably, the surface of the lithium-rich manganese-based cathode material is provided with a coating layer, the raw materials for preparing the coating layer including oxides and phosphates. By using oxides and phosphates as raw materials to coat the surface of the lithium-rich manganese-based cathode material, the energy barrier for oxygen release of the lithium-rich manganese-based cathode material can be greatly increased, thereby effectively stabilizing the surface oxygen of the lithium-rich manganese-based cathode material. Batteries assembled using this cathode material exhibit excellent cycle performance and effectively reduce the voltage decay of the lithium-rich manganese-based cathode material.

[0044] Preferably, the oxide includes at least one of Al2O3, ZrO2, and MnO2. However, it is not limited to the types listed above, and other inert metal oxides commonly used in the art are also applicable to this invention.

[0045] Preferably, the phosphate includes rare earth phosphates.

[0046] Preferably, the phosphate includes at least one of La(PO3)3, PrPO4 and Ca3(PO4)2.

[0047] Preferably, a modification layer is further disposed between the surface of the lithium-rich manganese-based cathode material and the coating layer. The modification layer is a spinel-structured lithium-rich manganese-based cathode material obtained by reacting the lithium-rich manganese-based cathode material with NH3 and CO2. The advantage of this arrangement is that the formation of the epitaxial spinel phase can enhance the Li... + The diffusion coefficient is improved, and the erosion of the positive electrode material by the electrolyte is suppressed.

[0048] Fourthly, the present invention provides a method for preparing a lithium-rich manganese-based cathode material as described in the third aspect, the method comprising the following steps:

[0049] (1) After mixing lithium salt and lithium-rich manganese-based precursor, the mixture is calcined at high temperature to obtain the lithium-rich manganese-based cathode material.

[0050] Preferably, the lithium salt includes at least one of lithium carbonate and lithium hydroxide.

[0051] Preferably, the lithium salt is ground and sieved before use to remove excessively large or small particles and ensure uniform particle size distribution.

[0052] Preferably, the high-temperature calcination includes: first heating to 50℃-80℃ (e.g., 50℃, 53℃, 56℃, 60℃, 62℃, 65℃, 67℃, 70℃, 74℃, 76℃, 78℃, or 80℃, etc.) and holding at that temperature for 6h-10h (e.g., 6h, 7h, 7.5h, 8h, 9h, or 10h, etc.), and then heating to 850℃-1100℃ (e.g., 850℃, 875℃, 890℃, 900℃, 915℃, 930℃, 950℃, 960℃, 970℃, 980℃, 990℃, 1000℃, 1050℃, or 1100℃, etc.) and holding at that temperature for 20h-26h (e.g., 20h, 21h, 22h, 23h, 24h, 25h, or 26h, etc.).

[0053] As a preferred technical solution for the preparation method of the lithium-rich manganese-based cathode material of the present invention, the preparation method further includes step (2):

[0054] The lithium-rich manganese-based cathode material prepared in step (1) is mixed with oxide and phosphate by ball milling and then heat-treated to obtain a lithium-rich manganese-based cathode material with a coating layer.

[0055] Preferably, the oxide is ground before use. The purpose is to reduce the particle size of the oxide, preferably controlling its particle size to the micro-nano or nano level.

[0056] In this invention, micro-nano refers to a particle size D50 greater than 100 nm and less than 1 μm, and nano-level refers to a particle size D50 less than 100 nm.

[0057] Preferably, the oxide accounts for 0.1%-0.5% of the mass of the lithium-rich manganese-based cathode material, for example, 0.1%, 0.2%, 0.3%, 0.4% or 0.5%.

[0058] Preferably, the phosphate is ground before use. The purpose is to reduce the particle size of the phosphate, preferably controlling its particle size to the micro-nano or nano level.

[0059] Preferably, the phosphate accounts for 0.1%-0.5% of the mass of the lithium-rich manganese-based cathode material, for example, 0.1%, 0.2%, 0.3%, 0.4%, or 0.5%. Preferably, the heat treatment temperature is 900℃-1100℃, for example, 900℃, 920℃, 950℃, 975℃, 1000℃, 1025℃, 1050℃, 1080℃, or 1100℃; and the heat treatment time is 8h-12h, for example, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, or 12h.

[0060] Preferably, the preparation method further includes modifying the lithium-rich manganese-based cathode material prepared in step (1) after step (1) and before step (2), wherein the modification method includes the following steps:

[0061] Lithium-rich manganese-based cathode material and NH4HCO3 are mixed and heated to decompose NH4HCO3 into CO2 and NH3, which then react with the lithium-rich manganese-based cathode material to form a spinel-structured lithium-rich manganese-based cathode material as a modification layer on the particle surface of the lithium-rich manganese-based cathode material.

[0062] Preferably, the mass ratio of the lithium-rich manganese-based cathode material to NH4HCO3 is 10:(0.5-3), such as 10:0.5, 10:0.8, 10:1, 10:1.2, 10:1.5, 10:1.8, 10:2, 10:2.2, 10:2.5, or 10:3.

[0063] Preferably, the heating temperature is 600℃-1000℃, such as 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃ or 1000℃.

[0064] Fifthly, the present invention provides a lithium-ion battery comprising the lithium-rich manganese-based cathode material as described in the third aspect.

[0065] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0066] Compared with existing technologies, the present invention has the following beneficial effects:

[0067] (1) This invention co-dops nickel-cobalt-manganese hydroxide with zirconium and tungsten, enabling the lithium-rich manganese-based cathode material prepared using this lithium-rich manganese-based precursor to exhibit high initial efficiency and excellent cycle performance. The battery assembled with the cathode material of this invention has an initial efficiency of over 82% and a capacity retention rate of over 89% after 50 cycles.

[0068] (2) The preparation method of the present invention is simple and suitable for industrial production. Detailed Implementation

[0069] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0070] In this embodiment of the invention, the molar ratio of Mn:Ni:Co = 2:2:6 is used as an example for illustrative purposes, but it is not limited to this. Other molar ratios are also applicable to this invention, and those skilled in the art can make adjustments as needed.

[0071] Example 1

[0072] I. Preparation of lithium-rich manganese-based precursors:

[0073] A method for preparing a lithium-rich manganese-based precursor includes the following steps:

[0074] (1) Preparation of nickel-cobalt-manganese mixed solution: Manganese sulfate, nickel sulfate and cobalt sulfate were dissolved in water according to the molar ratio of Mn:Ni:Co = 6:2:2 to obtain nickel-cobalt-manganese mixed solution;

[0075] (2) Preparation of the base solution: Add 600L of pure water to the reactor, and then add ammonia water to make the pH of the base solution 10.8;

[0076] (3) Prepare a 32% NaOH solution and an 18% ammonia solution by mixing the NaOH and ammonia solutions in a volume ratio of 8:3 to obtain a mixed alkaline solution;

[0077] (4) Dissolve Zr(SO4)2 in water to obtain a zirconium source solution with a concentration of 1 g / L, and dissolve ammonium tungstate in water to obtain a tungsten source solution with a concentration of 0.83 g / L;

[0078] (5) The above-mentioned nickel-cobalt-manganese mixed solution was added uniformly to the reactor containing the bottom liquid using a metering pump at a rate of 40 L / h. Simultaneously, a mixed alkaline solution was added to control the pH of the reaction system between 10.2 and 10.8. The temperature of the reaction system was 56℃. Stirring was started at 300 r / min. After the co-precipitation reaction began, the metering pumps controlling the feed of the zirconium source solution and the tungsten source solution were turned on. The zirconium source flow rate was 0.5 L / h, and the tungsten source flow rate was 0.3 L / h. The reaction continued to obtain the doped lithium-rich manganese-based precursor.

[0079] N2 is introduced throughout the reaction to prevent oxidation;

[0080] (6) After washing the lithium-rich manganese-based precursor, the material was spun dry using a centrifuge and placed in a hot air circulating drying oven at a drying temperature of 110°C. After drying, the material was sieved to obtain the lithium-rich manganese-based precursor.

[0081] The lithium-rich manganese-based precursor prepared in this embodiment is an element-doped nickel-cobalt-manganese hydroxide. The doping elements in the lithium-rich manganese-based precursor include Zr and W, wherein the molar ratio of manganese, nickel and cobalt is 6:2:2.

[0082] Based on the total mass of the lithium-rich manganese-based precursor, the doping amount of Zr is 2000 ppm, the doping amount of W is 1000 ppm, and the molar ratio of Zr to W is 2:1.

[0083] II. Preparation of lithium-rich manganese-based cathode materials:

[0084] (1) After grinding and sieving lithium carbonate, it is mixed evenly with the above-mentioned lithium-rich manganese-based precursor to obtain a mixture;

[0085] The molar ratio of Li to the metal element in the lithium-rich manganese-based precursor is 1.05:1.

[0086] (2) The mixture is placed in a roller kiln, heated to 50°C and held for 8 hours, then heated to 1000°C and held for 24 hours. After slow cooling, lithium-rich manganese-based cathode material is obtained. The cathode material matrix is ​​called the cathode material matrix.

[0087] (3) Al2O3 and La(PO3)3 are ground into nano-sized powder in a ball mill. The amount of Al2O3 added accounts for 0.2% of the mass of the cathode material matrix, and the amount of La(PO3)3 added accounts for 0.1% of the mass of the cathode material matrix. After the cathode material matrix and the ground Al2O3 and La(PO3)3 are thoroughly mixed in the ball mill, the material is placed in a roller kiln and heat-treated at 1000℃ for 10h in an air atmosphere to obtain lithium-rich manganese-based cathode material with a coating layer.

[0088] The lithium-rich manganese-based cathode material prepared in this embodiment is doped with Zr and W, and the surface of the lithium-rich manganese-based cathode material is coated with a coating layer.

[0089] Example 2

[0090] I. Preparation of lithium-rich manganese-based precursors:

[0091] A method for preparing a lithium-rich manganese-based precursor includes the following steps:

[0092] (1) Preparation of nickel-cobalt-manganese mixed solution: Manganese sulfate, nickel sulfate and cobalt sulfate were dissolved in water according to the molar ratio of Mn:Ni:Co = 6:2:2 to obtain nickel-cobalt-manganese mixed solution;

[0093] (2) Preparation of the base solution: Add 600L of pure water to the reactor, and then add ammonia water to make the pH of the base solution 10.5;

[0094] (3) Prepare a 30% NaOH solution and an 18% ammonia solution by mixing the NaOH and ammonia solutions in a volume ratio of 9:3 to obtain a mixed alkaline solution;

[0095] (4) Dissolve Zr(SO4)2 in water to obtain a zirconium source solution with a concentration of 2 g / L, and dissolve ammonium tungstate in water to obtain a tungsten source solution with a concentration of 1 g / L.

[0096] (5) The above-mentioned nickel-cobalt-manganese mixed solution was added to the reaction vessel containing the bottom liquid at a uniform rate of 60 L / h using a metering pump. At the same time, a mixed alkaline solution was added to control the pH of the reaction system to 10.5 and the temperature of the reaction system to 50°C. The stirring was turned on at a speed of 400 r / min. After the co-precipitation reaction started, the metering pumps controlling the feed of zirconium source solution and tungsten source solution were turned on. The flow rate of zirconium source was 0.4 L / h and the flow rate of tungsten source was 0.48 L / h. The reaction continued to obtain the doped lithium-rich manganese-based precursor.

[0097] N2 is introduced throughout the reaction to prevent oxidation;

[0098] (6) After washing the lithium-rich manganese-based precursor, the material was spun dry using a centrifuge and placed in a hot air circulating drying oven at a drying temperature of 100°C. After drying, the material was sieved to obtain the lithium-rich manganese-based precursor.

[0099] The lithium-rich manganese-based precursor prepared in this embodiment is an element-doped nickel-cobalt-manganese hydroxide. The doping elements in the lithium-rich manganese-based precursor include Zr and W, wherein the molar ratio of manganese, nickel and cobalt is 6:2:2.

[0100] Based on the total mass of the lithium-rich manganese-based precursor, the doping amount of Zr is 2500 ppm, the doping amount of W is 1500 ppm, and the molar ratio of Zr to W is 1.67:1.

[0101] II. Preparation of lithium-rich manganese-based cathode materials:

[0102] (1) After grinding and sieving lithium carbonate, it is mixed evenly with the above-mentioned lithium-rich manganese-based precursor to obtain a mixture;

[0103] The molar ratio of Li to the metal element in the lithium-rich manganese-based precursor is 1.03:1.

[0104] (2) The mixture is placed in a roller kiln, heated to 60°C and held for 7 hours, then heated to 1050°C and held for 22 hours. After slow cooling, lithium-rich manganese-based cathode material is obtained. The cathode material matrix is ​​called the cathode material matrix.

[0105] (3) Al2O3 and La(PO3)3 are ground into nano-sized powder in a ball mill. The amount of Al2O3 added accounts for 0.3% of the mass of the cathode material matrix, and the amount of La(PO3)3 added accounts for 0.3% of the mass of the cathode material matrix. After the cathode material matrix and the ground Al2O3 and La(PO3)3 are thoroughly mixed in the ball mill, the material is placed in a roller kiln and heat-treated at 900℃ for 12h in an air atmosphere to obtain a lithium-rich manganese-based cathode material with a coating layer.

[0106] The lithium-rich manganese-based cathode material prepared in this embodiment is doped with Zr and W, and the surface of the lithium-rich manganese-based cathode material is coated with a coating layer.

[0107] Example 3

[0108] I. Preparation of lithium-rich manganese-based precursors:

[0109] A method for preparing a lithium-rich manganese-based precursor includes the following steps:

[0110] (1) Preparation of nickel-cobalt-manganese mixed solution: Manganese sulfate, nickel sulfate and cobalt sulfate were dissolved in water according to the molar ratio of Mn:Ni:Co = 6:2:2 to obtain nickel-cobalt-manganese mixed solution;

[0111] (2) Preparation of the base solution: Add 600L of pure water to the reactor, and then add ammonia water to make the pH of the base solution 10.2;

[0112] (3) Prepare a 28% NaOH solution and a 20% ammonia solution by mixing the NaOH and ammonia solutions in a volume ratio of 2:1 to obtain a mixed alkaline solution;

[0113] (4) Dissolve Zr(SO4)2 in water to obtain a zirconium source solution with a concentration of 2.5 g / L, and dissolve ammonium tungstate in water to obtain a tungsten source solution with a concentration of 2 g / L;

[0114] (5) The above-mentioned nickel-cobalt-manganese mixed solution was added to the reaction vessel containing the bottom liquid at a uniform rate of 40 L / min using a metering pump. At the same time, mixed alkaline solution was added to control the pH of the reaction system to 10.2 and the temperature of the reaction system to 60℃. Stirring was turned on at a speed of 250 r / min. After the co-precipitation reaction started, the metering pumps controlling the feed of zirconium source solution and tungsten source solution were turned on. The zirconium source flow rate was 1 L / h and the tungsten source flow rate was 0.56 L / h. The reaction continued to obtain the doped lithium-rich manganese-based precursor.

[0115] N2 is introduced throughout the reaction to prevent oxidation;

[0116] (6) After washing the lithium-rich manganese-based precursor, the material was spun dry using a centrifuge and placed in a hot air circulating drying oven at a drying temperature of 95°C. After drying, the material was sieved to obtain the lithium-rich manganese-based precursor.

[0117] The lithium-rich manganese-based precursor prepared in this embodiment is an element-doped nickel-cobalt-manganese hydroxide. The doping elements in the lithium-rich manganese-based precursor include Zr and W, wherein the molar ratio of manganese, nickel and cobalt is 6:2:2.

[0118] Based on the total mass of the lithium-rich manganese-based precursor, the doping amount of Zr is 1800 ppm, the doping amount of W is 800 ppm, and the molar ratio of Zr to W is 2.25:1.

[0119] II. Preparation of lithium-rich manganese-based cathode materials:

[0120] (1) After grinding and sieving lithium carbonate, it is mixed evenly with the above-mentioned lithium-rich manganese-based precursor to obtain a mixture;

[0121] The molar ratio of Li to the metal element in the lithium-rich manganese-based precursor is 1.06:1.

[0122] (2) The mixture is placed in a roller kiln, heated to 70°C and held for 6 hours, then heated to 900°C and held for 25 hours. After slow cooling, lithium-rich manganese-based cathode material is obtained. The cathode material matrix is ​​called the cathode material matrix.

[0123] (3) Al2O3 and La(PO3)3 are ground into nano-sized powder in a ball mill. The amount of Al2O3 added accounts for 0.2% of the mass of the cathode material matrix, and the amount of La(PO3)3 added accounts for 0.4% of the mass of the cathode material matrix. After the cathode material matrix and the ground Al2O3 and La(PO3)3 are thoroughly mixed in the ball mill, the material is placed in a roller kiln and heat-treated at 1100℃ for 8 hours in an air atmosphere to obtain a lithium-rich manganese-based cathode material with a coating layer.

[0124] The lithium-rich manganese-based cathode material prepared in this embodiment is doped with Zr and W, and the surface of the lithium-rich manganese-based cathode material is coated with a coating layer.

[0125] Example 4

[0126] I. A lithium-rich manganese-based precursor and its preparation method. The difference between the preparation method of the lithium-rich manganese-based precursor and that of Example 1 is that, in step (5), a chromium sulfate solution is prepared, and the chromium sulfate solution and a nickel-cobalt-manganese mixed solution are added to the reactor in parallel flow. The doping elements in the lithium-rich manganese-based precursor prepared in this example include Zr, W, and Cr, with Zr doping amount of 2000 ppm, W doping amount of 1000 ppm, and Cr doping amount of 1000 ppm.

[0127] II. A lithium-rich manganese-based cathode material and its preparation method, wherein the preparation method of the lithium-rich manganese-based cathode material differs from that of Example 1 only in that the lithium-rich manganese-based precursor of this example is used instead of the lithium-rich manganese-based precursor of Example 1.

[0128] Example 5

[0129] I. A lithium-rich manganese-based precursor and its preparation method, which differs from Example 1 in that the feed rate of the zirconium source solution in the preparation method is changed so that the doping amount of Zr in the lithium-rich manganese-based precursor is 900 ppm, and the molar ratio of Zr to W is 0.9:1.

[0130] II. A lithium-rich manganese-based cathode material and its preparation method, wherein the preparation method of the lithium-rich manganese-based cathode material differs from that of Example 1 only in that the lithium-rich manganese-based precursor of this example is used instead of the lithium-rich manganese-based precursor of Example 1.

[0131] Example 6

[0132] I. A lithium-rich manganese-based precursor and its preparation method, which differs from Example 1 only in that the feed rate of the zirconium source solution in the preparation method is changed so that the doping amount of Zr element in the lithium-rich manganese-based precursor is 3200ppm, at which time the molar ratio of Zr to W is 3.2:1.

[0133] II. A lithium-rich manganese-based cathode material and its preparation method, wherein the preparation method of the lithium-rich manganese-based cathode material differs from that of Example 1 only in that the lithium-rich manganese-based precursor of this example is used instead of the lithium-rich manganese-based precursor of Example 1.

[0134] Example 7

[0135] I. A lithium-rich manganese-based precursor and its preparation method, which differs from Example 1 only in that the feed rate of the zirconium source solution in the preparation method is changed so that the doping amount of W element in the lithium-rich manganese-based precursor is 600 ppm, at which time the molar ratio of Zr to W is 3.34:1.

[0136] II. A lithium-rich manganese-based cathode material and its preparation method, wherein the preparation method of the lithium-rich manganese-based cathode material differs from that of Example 1 only in that the lithium-rich manganese-based precursor of this example is used instead of the lithium-rich manganese-based precursor of Example 1.

[0137] Example 8

[0138] I. A lithium-rich manganese-based precursor and its preparation method, which differs from Example 1 only in that the feed rate of the tungsten source solution in the preparation method is changed so that the doping amount of W element in the lithium-rich manganese-based precursor is 1600 pm, at which time the molar ratio of Zr to W is 1.25:1.

[0139] II. A lithium-rich manganese-based cathode material and its preparation method, wherein the preparation method of the lithium-rich manganese-based cathode material differs from that of Example 1 only in that the lithium-rich manganese-based precursor of this example is used instead of the lithium-rich manganese-based precursor of Example 1.

[0140] Example 9

[0141] I. A lithium-rich manganese-based precursor and its preparation method, which is the same as in Example 1.

[0142] II. A lithium-rich manganese-based cathode material and its preparation method. The difference between the preparation method of the lithium-rich manganese-based cathode material in Example 1 is that, after step (2) and before step (3), the following operations are performed:

[0143] The lithium-rich manganese-based cathode material and NH4HCO3 are mixed at a mass ratio of 10:1 and heated to 850°C to decompose NH4HCO3 into CO2 and NH3, which then react with the lithium-rich manganese-based cathode material to form a spinel-structured lithium-rich manganese-based cathode material as a modification layer on the surface of the lithium-rich manganese-based cathode material particles. Accordingly, the lithium-rich manganese-based cathode material in step (3) is replaced with the lithium-rich manganese-based cathode material with the modification layer.

[0144] Example 10

[0145] I. A lithium-rich manganese-based precursor and its preparation method, which is the same as in Example 1.

[0146] II. A lithium-rich manganese-based cathode material and its preparation method. The difference between the preparation method of the lithium-rich manganese-based cathode material in Example 1 is that La(PO3)3 is replaced with an equal mass of Al2O3. The coating layer of the lithium-rich manganese-based cathode material prepared in this example is an alumina coating layer.

[0147] Comparative Example 1

[0148] I. A lithium-rich manganese-based precursor and its preparation method, the only difference from Example 1 is that no zirconium source solution is added in the preparation method, so that the lithium-rich manganese-based precursor does not contain Zr.

[0149] II. A lithium-rich manganese-based cathode material and its preparation method, wherein the preparation method of the lithium-rich manganese-based cathode material differs from that of Example 1 only in that the lithium-rich manganese-based precursor of this comparative example is used instead of the lithium-rich manganese-based precursor of Example 1.

[0150] Comparative Example 2

[0151] I. A lithium-rich manganese-based precursor and its preparation method, the only difference from Example 1 is that the tungsten source solution is not added in the preparation method, so that the lithium-rich manganese-based precursor does not contain W element.

[0152] II. A lithium-rich manganese-based cathode material and its preparation method, wherein the preparation method of the lithium-rich manganese-based cathode material differs from that of Example 1 only in that the lithium-rich manganese-based precursor of this comparative example is used instead of the lithium-rich manganese-based precursor of Example 1.

[0153] Battery assembly:

[0154] Cathodes were prepared using the lithium-rich manganese-based cathode materials of Examples 1-7 and Comparative Examples 1-3, and batteries were assembled. Specifically:

[0155] The cathode materials obtained in the examples and comparative examples were used to prepare coin cells. The specific preparation method was as follows: the cathode material was homogenized and coated in a ratio of 90 (main material): 5 (polyvinylidene fluoride PVDF): 5 (conductive agent acetylene black) to form an electrode sheet. A lithium metal sheet was used as the counter electrode, and the separator was Celgard 2500. A 1 mol / L lithium hexafluorophosphate solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) (EC to DMC volume ratio of 1:1) was used as the electrolyte. The CR2032 coin cell was assembled in an argon glove box (where water < 0.01 ppm and oxygen < 0.01 ppm). Finally, the battery was placed in the Blue Electric Test System for electrical performance testing.

[0156] The electrical performance test conditions were as follows: charge and discharge voltage range of 2.0V-4.8V, test temperature of 25℃, 0.1C / 0.1C cycle for 1 week to test the first charge and discharge capacity of the battery and calculate the first efficiency, 1C / 1C cycle for 50 weeks to test the cycle performance of the battery. The results are shown in Table 1 below.

[0157] Table 1

[0158]

[0159] As shown in Table 1, the present invention, by co-doping nickel-cobalt-manganese hydroxide with zirconium and tungsten, enables the lithium-rich manganese-based cathode material prepared using this lithium-rich manganese-based precursor to exhibit high initial efficiency and excellent cycle performance. Comparative Example 1 only underwent tungsten doping, and Comparative Example 2 only underwent zirconium doping, both resulting in only a minor improvement in electrochemical performance.

[0160] A comparison of Examples 1 and 4 shows that further chromium doping can further improve the electrochemical performance.

[0161] A comparison of Examples 1 and 5-6 shows that Zr doping and substitution can stabilize the layered structure by generating a "pinning effect" and a "columnar effect," thus promoting the growth of Li. + The diffusion of zirconium increases the electronic and ionic conductivity of lithium-rich manganese-based cathode materials. The doping amount of zirconium is preferably in the range of 1000-3000 ppm, which can better improve the electrochemical performance of the material.

[0162] A comparison of Examples 1 and 7-8 shows that the addition of W can form strong covalent bonds with O, thereby stabilizing the crystal structure. The doping amount of tungsten is preferably in the range of 700ppm-1500ppm, which can better improve the electrochemical performance of its lithium-rich layered oxide.

[0163] A comparison of Examples 1 and 9 shows that by setting a modification layer, Li can be... + The migration provides a three-dimensional channel, shortening the Li + The migration path can comprehensively improve the kinetic properties and thermodynamic stability of materials.

[0164] A comparison of Examples 1 and 10 shows that using oxides and phosphates as raw materials for co-coating, compared with coating only oxides, helps to increase the energy barrier for oxygen release in lithium-rich manganese-based cathode materials, thereby stabilizing the surface oxygen of lithium-rich manganese-based cathode materials and improving electrochemical performance, especially cycle performance.

[0165] The applicant declares that the detailed method of the present invention is illustrated by the above embodiments, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A lithium-rich manganese-based cathode material, characterized in that, The lithium-rich manganese-based cathode material was prepared using a lithium-rich manganese-based precursor. The lithium-rich manganese-based precursor is an element-doped nickel-cobalt-manganese hydroxide, and the doping elements in the lithium-rich manganese-based precursor include Zr and W. The surface of the lithium-rich manganese-based cathode material is sequentially provided with a modified layer and a coating layer; The lithium-rich manganese-based cathode material is prepared by the following method, which includes the following steps: (1) After mixing lithium salt and lithium-rich manganese-based precursor, calcining at high temperature to obtain the lithium-rich manganese-based cathode material, mixing the lithium-rich manganese-based cathode material matrix with NH4HCO3, heating to decompose NH4HCO3 into CO2 and NH3, and reacting with the lithium-rich manganese-based cathode material matrix, forming a spinel-structured lithium-rich manganese-based cathode material as a modification layer on the particle surface of the lithium-rich manganese-based cathode material matrix; (2) After the lithium-rich manganese-based cathode material prepared in step (1) is ball-milled and mixed with oxide and phosphate, it is heat-treated once to obtain a lithium-rich manganese-based cathode material with a coating layer.

2. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, In the lithium-rich manganese-based precursor, the molar ratio of manganese, nickel and cobalt is x:y:z, where x>0.5, 0.4>y>0.01, 0.4>z>0.01, and x+y+z<1.

3. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, Based on the total mass of the lithium-rich manganese-based precursor, the Zr doping amount is 1000ppm-3000ppm.

4. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, Based on the total mass of the lithium-rich manganese-based precursor, the doping amount of W element is 700ppm-1500ppm.

5. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, The molar ratio of Zr to W is (1.5-3):

1.

6. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, The doping elements also include Cr.

7. The lithium-rich manganese-based cathode material according to claim 6, characterized in that, The ratio of the total molar amount of Zr and W to the molar amount of Cr is (1.5-4):

1.

8. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, The particle size of the lithium-rich manganese-based precursor is 5μm-10μm.

9. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, The preparation method of the lithium-rich manganese-based precursor includes the following steps: Prepare a nickel-cobalt-manganese mixed solution, a base solution, a precipitant solution, a complexing agent solution, a zirconium source solution, and a tungsten source solution; The nickel-cobalt-manganese mixed solution, precipitant solution, and complexing agent solution are added to a reaction vessel containing a base liquid. The temperature and pH of the reaction system are controlled to preset values. After the coprecipitation reaction begins, zirconium source solution and tungsten source solution are added, and the reaction continues to obtain a lithium-rich manganese-based precursor.

10. The lithium-rich manganese-based cathode material according to claim 9, characterized in that, The nickel-cobalt-manganese mixed solution is added at a rate of 10 L / h to 100 L / h.

11. The lithium-rich manganese-based cathode material according to claim 9, characterized in that, The zirconium source in the zirconium source solution includes at least one of Zr(SO4)2, CH4NO3Zr, and Zr(O2CCH3)4.

12. The lithium-rich manganese-based cathode material according to claim 9, characterized in that, The concentration of the zirconium source solution is 0.1 g / L-3 g / L.

13. The lithium-rich manganese-based cathode material according to claim 9, characterized in that, The flow rate of the zirconium source solution is 0.3 L / h to 3 L / h.

14. The lithium-rich manganese-based cathode material according to claim 9, characterized in that, The tungsten source in the tungsten source solution includes at least one of ammonium tungstate and Na2WO4.

15. The lithium-rich manganese-based cathode material according to claim 9, characterized in that, The concentration of the tungsten source solution is 0.1 g / L-3 g / L.

16. The lithium-rich manganese-based cathode material according to claim 9, characterized in that, The flow rate of the tungsten source solution is 0.3 L / h to 3 L / h.

17. The lithium-rich manganese-based cathode material according to claim 9, characterized in that, The preparation method further includes: preparing a chromium source solution, and adding the chromium source solution and the nickel-cobalt-manganese mixed solution in parallel into a container to perform chromium doping.

18. The lithium-rich manganese-based cathode material according to claim 9, characterized in that, The preset temperature is 40℃-65℃, and the preset pH is 9.5-11.

5.

19. The lithium-rich manganese-based cathode material according to claim 9, characterized in that, After controlling the temperature and pH of the reaction system to preset values, stirring is started, and the zirconium source solution and tungsten source solution are added under stirring conditions. The stirring speed is 200 r / min-400 r / min.

20. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, The oxide includes at least one of Al2O3, ZrO2 and MnO2.

21. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, The phosphates include rare earth phosphates.

22. The lithium-rich manganese-based cathode material according to claim 21, characterized in that, The phosphate includes at least one of La(PO3)3, PrPO4 and Ca3(PO4)2.

23. A method for preparing the lithium-rich manganese-based cathode material as described in claim 1, characterized in that, The preparation method includes the following steps: (1) After mixing lithium salt and lithium-rich manganese-based precursor, calcining at high temperature, the lithium-rich manganese-based cathode material is obtained, which is referred to as cathode material matrix; the lithium-rich manganese-based cathode material matrix is ​​mixed with NH4HCO3, heated to decompose NH4HCO3 into CO2 and NH3, and reacted with the lithium-rich manganese-based cathode material matrix to form a spinel structure lithium-rich manganese-based cathode material as a modification layer on the particle surface of the lithium-rich manganese-based cathode material matrix; (2) After the lithium-rich manganese-based cathode material prepared in step (1) is ball-milled and mixed with oxide and phosphate, it is heat-treated once to obtain a lithium-rich manganese-based cathode material with a coating layer.

24. The method for preparing lithium-rich manganese-based cathode material according to claim 23, characterized in that, The lithium salt includes at least one of lithium carbonate and lithium hydroxide.

25. The method for preparing lithium-rich manganese-based cathode material according to claim 23, wherein the lithium salt is ground and sieved before use.

26. The method for preparing lithium-rich manganese-based cathode material according to claim 23, wherein the high-temperature calcination comprises: First, raise the temperature to 50℃-80℃ and hold for 6-10 hours, then raise the temperature to 850℃-1100℃ and hold for 20-26 hours.

27. The method for preparing lithium-rich manganese-based cathode material according to claim 23, wherein the oxide is ground before use.

28. The method for preparing lithium-rich manganese-based cathode material according to claim 23, wherein the mass of the oxide accounts for 0.1%-0.5% of the mass of the cathode material matrix.

29. The method for preparing lithium-rich manganese-based cathode material according to claim 23, wherein the phosphate is ground before use.

30. The method for preparing lithium-rich manganese-based cathode material according to claim 23, wherein the mass of the phosphate accounts for 0.1%-0.5% of the mass of the cathode material matrix.

31. The method for preparing lithium-rich manganese-based cathode material according to claim 23, wherein the heat treatment temperature is 900℃-1100℃ and the heat treatment time is 8h-12h.

32. The method for preparing lithium-rich manganese-based cathode material according to claim 23, wherein the mass ratio of the lithium-rich manganese-based cathode material to NH4HCO3 is 10:(0.5-3).

33. The method for preparing lithium-rich manganese-based cathode material according to claim 23, wherein the heating temperature is 600℃-1000℃.

34. A lithium-ion battery, characterized in that, The lithium-ion battery includes the lithium-rich manganese-based cathode material as described in any one of claims 1-22.

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