Lithium-rich manganese-based precursor, and preparation method therefor and use thereof

Abstract

The present application discloses a lithium-rich manganese-based precursor, and a preparation method therefor and a use thereof. The lithium-rich manganese-based precursor is an element-doped nickel-cobalt-manganese hydroxide, and doping elements in the lithium-rich manganese-based precursor include zirconium (Zr) and tungsten (W). In the present application, co-doping of the nickel-cobalt-manganese hydroxide with Zr and W helps to improve the electrochemical properties of a material, especially the cycle performance and the initial coulombic efficiency.

Description

A lithium-rich manganese-based precursor, and its preparation method and application Technical Field

[0001] The present application belongs to the field of lithium battery technology, and specifically relates to a lithium-rich manganese-based precursor, and a preparation method and application thereof. Background Art

[0002] Lithium-rich manganese-based cathode materials have attracted widespread attention due to their high energy density and high discharge capacity. However, they have low electrical conductivity, and the contact resistance between the electrode and the electrolyte increases during high-rate charge and discharge. Combined with concentration polarization and side reactions, these materials exhibit poor performance at high-rate charge and discharge in actual power battery applications, resulting in low initial charge and discharge coulombic efficiency and poor cycling performance. This leaves them far from practical application.

[0003] CN108557905A discloses a lithium-rich manganese-based material precursor, which is a lithium-rich manganese-based material carbonate precursor with a flaky morphology. The preparation process of the lithium-rich manganese-based material precursor includes: simultaneously metering and pumping a mixed salt solution, a precipitant, and a complexing agent into a reactor at a speed of 0.12L / h-0.9L / h, controlling the reaction temperature to 35°C-65°C, the pH value to 7.5-8.5, and the stirring speed to 400rpm / min-1000rpm / min. After the reaction is completed, the material is aged for 5h-20h, and the precipitate is separated, washed, and dried to obtain a flaky lithium-rich manganese-based material carbonate precursor. However, in the process of preparing the lithium-rich manganese-based material precursor, this method makes it difficult to control the particle size of the lithium-rich manganese-based material precursor, and it is easy to obtain 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 positive electrode material. The method comprises: preparing a mixed solution A, a mixed solution B, and a solution C with different manganese ion contents, and successively 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 a cyclic reaction to obtain a gradient lithium-rich manganese-based precursor. However, the preparation process of this method is complicated and difficult to industrialize.

[0005] Therefore, providing a simple preparation method for lithium-rich manganese-based positive electrode materials so that they have high first efficiency and excellent cycle performance is a technical problem that needs to be solved urgently.

[0006] Summary of the Invention

[0007] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0008] In response to the above-mentioned problems existing in the prior art, the purpose of this application is to propose a lithium-rich manganese-based precursor, its preparation method and application. This application dopes the lithium-rich manganese-based precursor with specific elements, so that the lithium-rich manganese-based positive electrode material prepared using the lithium-rich manganese-based precursor has a high first efficiency, excellent cycle performance, and good resistance to voltage decay.

[0009] To achieve the above objectives, this application adopts the following technical solutions:

[0010] In a first aspect, the present application 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.

[0011] The present application co-dopes nickel-cobalt-manganese hydroxide with zirconium and tungsten, which helps to improve the electrochemical performance of the material, especially the cycle performance and first efficiency.

[0012] The following are optional technical solutions for this application, but are not intended to limit the technical solutions provided in this application. Through the following optional technical solutions, the technical objectives and beneficial effects of this application can be better achieved and realized.

[0013] In one embodiment, in the lithium-rich manganese-based precursor, the molar ratio of manganese, nickel and cobalt is x:y:z, wherein x>0.5, 0.4>y>0.01, 0.4>z>0.01, and x+y+z<1.

[0014] In one embodiment, based on the total mass of the lithium-rich manganese-based precursor, the doping amount of the Zr element is 1000ppm-3000ppm, for example, 1000ppm, 1200ppm, 1400ppm, 1500ppm, 1750ppm, 1800ppm, 2000ppm, 2100ppm, 2200ppm, 2300ppm, 2400ppm, 2500ppm, 2600ppm, 2700ppm, 2800ppm, 2900ppm or 3000ppm, etc.

[0015] In one embodiment, based on the total mass of the lithium-rich manganese-based precursor, the doping amount of the W element is 700ppm-1500ppm, for example, 700ppm, 800ppm, 900ppm, 1000ppm, 1100ppm, 1200ppm, 1300ppm, 1400ppm or 1500ppm.

[0016] In one embodiment, 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.

[0017] By limiting the doping amount of Zr element, the doping amount of W element, and the molar ratio of Zr and W, the composition and structure of the lithium-rich manganese-based precursor can be further regulated and optimized, thereby improving the electrochemical performance of the lithium-rich manganese-based positive electrode material prepared using it.

[0018] In one embodiment, the doping element further includes Cr.

[0019] In one embodiment, 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.

[0020] By further doping a certain amount of chromium on the basis of co-doping with zirconium and tungsten, a synergistic effect can be achieved, so that the electrochemical performance of the lithium-rich manganese-based positive electrode material prepared by using it can be further improved.

[0021] In one embodiment, the particle size of the lithium-rich manganese-based precursor is 5 μm-10 μm, for example, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm or 10 μm.

[0022] In a second aspect, the present application provides a method for preparing the lithium-rich manganese-based precursor as described in the first aspect, the method comprising the following steps:

[0023] Prepare nickel-cobalt-manganese mixed solution, base solution, precipitant solution, complexing agent solution, zirconium source solution and tungsten source solution;

[0024] 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, and after the coprecipitation reaction begins, the zirconium source solution and the tungsten source solution are added and the reaction is continued to obtain a lithium-rich manganese-based precursor.

[0025] In the method of the present application, the preparation order of the nickel-cobalt-manganese mixed solution, base solution, precipitant solution, complexing agent solution, zirconium source solution and tungsten source solution is not specific and can be prepared simultaneously or sequentially, and the present application does not make specific limitations.

[0026] In the method of the present application, when the temperature and pH are controlled to preset values, a coprecipitation reaction occurs to form nickel-cobalt-manganese hydroxide. After the coprecipitation reaction begins, a zirconium source solution and a tungsten source solution are added to achieve co-doping of zirconium and tungsten, thereby obtaining a lithium-rich manganese-based precursor with excellent performance. Furthermore, the method is simple and suitable for industrial production.

[0027] It should be noted that in the present application, the zirconium source solution and the tungsten source solution should be added after the temperature and pH reach the preset values, that is, after the co-precipitation reaction begins. If these two dispersions are first added to the reaction vessel containing the base liquid at the same stage with the nickel-cobalt-manganese mixed solution, the precipitant solution and the complexing agent solution, and then the temperature and pH are controlled, the reaction product will not be the desired precursor material.

[0028] In the present application, the nickel-cobalt-manganese solution refers to a solution containing nickel, cobalt and manganese elements, which can be prepared by dissolving nickel salt, cobalt salt and manganese salt in water.

[0029] In one embodiment, the base liquid is prepared by adding water to a reactor, and then adding ammonia water to make the pH of the base liquid reach 9.5-11.5, such as 9.5, 9.8, 10, 10.3, 10.5, 10.7, 11, 11.2 or 11.5.

[0030] In one embodiment, the precipitant solution is a NaOH solution or a KOH solution with a mass concentration of 25%-35% (eg, 25%, 27%, 28%, 30%, 31%, 32%, 33% or 35%).

[0031] In one embodiment, the complexing agent solution is an aqueous ammonia solution with a mass concentration of 15%-25% (eg, 15%, 16%, 18%, 19%, 20%, 22%, 23% or 25%).

[0032] In the method of the present application, the precipitant solution and the complexing agent solution can be added to the reaction container separately, or the two can be mixed before adding to the reaction container.

[0033] In one embodiment, the addition rate of the nickel-cobalt-manganese mixed solution is 10 L / h-100 L / h, for example, 10 L / h, 20 L / h, 30 L / h, 40 L / h, 50 L / h, 60 L / h, 70 L / h, 80 L / h, 90 L / h or 100 L / h.

[0034] In one embodiment, the zirconium source in the zirconium source solution includes at least one of Zr(SO4)2, CH4NO3Zr and Zr(O2CCH3)4;

[0035] In one embodiment, the concentration of the zirconium source solution is 0.1 g / L-3 g / L, for example, 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, etc.

[0036] In one embodiment, the flow rate of the zirconium source solution is 0.3 L / h-3 L / h, for example, 0.3 L / h, 0.4 L / h, 0.5 L / h, 0.6 L / h, 0.8 L / h, 1 L / h, 1.2 L / h, 1.5 L / h, 1.8 L / h, 2 L / h, 2.5 L / h or 3 L / h, etc.

[0037] In one embodiment, the tungsten source in the tungsten source solution includes at least one of ammonium tungstate and Na2WO4.

[0038] In one embodiment, the concentration of the tungsten source solution is 0.1 g / L-3 g / L, for example, 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, etc.

[0039] In one embodiment, the flow rate of the tungsten source solution is 0.3 L / h-3 L / h, for example, 0.3 L / h, 0.4 L / h, 0.5 L / h, 0.6 L / h, 0.8 L / h, 1 L / h, 1.2 L / h, 1.5 L / h, 1.8 L / h, 2 L / h, 2.5 L / h or 3 L / h.

[0040] In one embodiment, the preparation method further comprises: preparing a chromium source solution, and adding the chromium source solution and the nickel-cobalt-manganese mixed solution into a container in parallel to perform chromium doping.

[0041] In one embodiment, the preset value of the temperature is 40°C-65°C, for example, 40°C, 43°C, 45°C, 46°C, 48°C, 50°C, 52°C, 55°C, 58°C, 60°C, 63°C or 65°C; the preset value of the pH is 9.5-11.5, for example, 9.5, 9.8, 10, 10.3, 10.5, 10.7, 11, 11.2 or 11.5.

[0042] In one embodiment, after controlling the temperature and pH of the reaction system to predetermined values, stirring is started, and the zirconium source solution and the tungsten source solution are added under stirring at a speed of 200-400 r / min (e.g., 200 r / min, 250 r / min, 300 r / min, 350 r / min, or 400 r / min). Stirring during the addition and reaction process can improve the dispersion uniformity of the reaction, which is beneficial for improving product performance.

[0043] In a third aspect, the present application provides a lithium-rich manganese-based positive electrode material, wherein the lithium-rich manganese-based positive electrode material is prepared using the lithium-rich manganese-based precursor as described in the first aspect, and the lithium-rich manganese-based positive electrode material is doped with Zr and W.

[0044] In one embodiment, the lithium-rich manganese-based positive electrode material is further doped with Cr.

[0045] In one embodiment, the surface of the lithium-rich manganese-based positive electrode material is provided with a coating layer, and the raw materials for preparing the coating layer include oxides and phosphates. By using oxides and phosphates as raw materials to coat the surface of the lithium-rich manganese-based positive electrode material, the energy barrier for oxygen release from the lithium-rich manganese-based positive electrode material can be greatly increased, thereby effectively stabilizing the surface oxygen of the lithium-rich manganese-based positive electrode material. Batteries assembled using this positive electrode material exhibit excellent cycling performance and effectively reduce the voltage decay of the lithium-rich manganese-based positive electrode material.

[0046] In one embodiment, the oxide includes at least one of Al2O3, ZrO2, and MnO2. However, the oxide is not limited to the above-mentioned types, and other inert metal oxides commonly used in the art are also applicable to the present application.

[0047] In one embodiment, the phosphate comprises a rare earth phosphate.

[0048] In one embodiment, the phosphate includes at least one of La(PO3)3, PrPO4 and Ca3(PO4)2.

[0049] In one embodiment, a modified layer is further provided between the surface of the lithium-rich manganese-based positive electrode material and the coating layer, and the modified layer is a lithium-rich manganese-based positive electrode material having a spinel structure obtained by reacting the lithium-rich manganese-based positive electrode material with NH3 and CO2. The advantage of such a setting is that the formation of the epitaxial spinel phase can improve the Li + diffusion coefficient and inhibit the corrosion of the electrolyte on the positive electrode material.

[0050] In a fourth aspect, the present application provides a method for preparing the lithium-rich manganese-based positive electrode material as described in the third aspect, the preparation method comprising the following steps:

[0051] (1) After mixing the lithium salt and the lithium-rich manganese-based precursor, calcining at high temperature to obtain the lithium-rich manganese-based positive electrode material.

[0052] In one embodiment, the lithium salt includes at least one of lithium carbonate and lithium hydroxide.

[0053] In one embodiment, the lithium salt is ground and sieved before use to remove oversized or undersized particles and ensure uniform particle size distribution.

[0054] In one embodiment, the high temperature calcination includes: first heating the temperature to 50°C-80°C (for example, 50°C, 53°C, 56°C, 60°C, 62°C, 65°C, 67°C, 70°C, 74°C, 76°C, 78°C or 80°C, etc.) and keeping it warm for 6h-10h (for example, 6h, 7h, 7.5h, 8h, 9h or 10h, etc.), and then heating the temperature to 850°C-1100°C (for example, 850°C, 875°C, 890°C, 900°C, 915°C, 930°C, 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, 1050°C or 1100°C, etc.) and keeping it warm for 20h-26h (for example, 20h, 21h, 22h, 23h, 24h, 25h or 26h, etc.).

[0055] As an optional technical solution of the preparation method of the lithium-rich manganese-based positive electrode material described in the present application, the preparation method further includes step (2):

[0056] The lithium-rich manganese-based positive electrode 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 positive electrode material with a coating layer.

[0057] In one embodiment, the oxide is ground before use to reduce the particle size of the oxide, preferably to a micro-nano or nanometer level.

[0058] In this application, 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.

[0059] In one embodiment, the mass of the oxide accounts for 0.1%-0.5% of the mass of the lithium-rich manganese-based positive electrode material, such as 0.1%, 0.2%, 0.3%, 0.4% or 0.5%.

[0060] In one embodiment, the phosphate is ground before use to reduce the particle size of the phosphate, preferably to the micro-nano or nanometer level.

[0061] In one embodiment, the mass of the phosphate accounts for 0.1%-0.5% of the mass of the lithium-rich manganese-based positive electrode material, such as 0.1%, 0.2%, 0.3%, 0.4% or 0.5%.

[0062] In one embodiment, the heat treatment temperature is 900°C-1100°C, for example, 900°C, 920°C, 950°C, 975°C, 1000°C, 1025°C, 1050°C, 1080°C or 1100°C, etc.; the heat treatment time is 8h-12h, for example, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h or 12h, etc.

[0063] In one embodiment, the preparation method further comprises, after step (1) and before step (2), performing a modification treatment on the lithium-rich manganese-based positive electrode material prepared in step (1), wherein the modification treatment method comprises the following steps:

[0064] The lithium-rich manganese-based positive electrode material and NH4HCO3 are mixed, and the NH4HCO3 is heated to decompose CO2 and NH3, which react with the lithium-rich manganese-based positive electrode material to epitaxially form a spinel-structured lithium-rich manganese-based positive electrode material as a modified layer on the surface of the lithium-rich manganese-based positive electrode material particles.

[0065] In one embodiment, the mass ratio of the lithium-rich manganese-based positive electrode material to NH4HCO3 is 10:(0.5-3), for example, 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, etc.

[0066] In one embodiment, the heating temperature is 600°C-1000°C, for example, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C or 1000°C.

[0067] In a fifth aspect, the present application provides a lithium-ion battery, which includes the lithium-rich manganese-based positive electrode material as described in the third aspect.

[0068] The numerical range described in this application includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to limited space and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0069] Compared with existing technical performance, this application has the following beneficial effects:

[0070] (1) This application co-dopes nickel-cobalt-manganese hydroxide with zirconium and tungsten, resulting in a lithium-rich manganese-based positive electrode material prepared using this lithium-rich manganese-based precursor with high initial efficiency and excellent cycling performance. Batteries assembled with this positive electrode material exhibit an initial efficiency exceeding 82% and a 50-cycle capacity retention rate exceeding 89%.

[0071] (2) The preparation method of the present application is simple and suitable for industrial production.

[0072] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0073] The technical solution of this application is further explained below through specific implementation methods.

[0074] In the embodiments of the present application, the molar ratio of Mn:Ni:Co is taken as 2:2:6 for illustrative description, but it is not limited thereto. Other molar ratios are also applicable to the present application, and those skilled in the art can adjust them as needed.

[0075] Example 1

[0076] Ⅰ. Preparation of lithium-rich manganese-based precursor:

[0077] A method for preparing a lithium-rich manganese-based precursor comprises the following steps:

[0078] (1) preparing a nickel-cobalt-manganese mixed solution: dissolving manganese sulfate, nickel sulfate, and cobalt sulfate in water at a molar ratio of Mn:Ni:Co = 6:2:2 to obtain a nickel-cobalt-manganese mixed solution;

[0079] (2) Preparation of the base solution: Add 600 L of pure water to the reactor, and then add ammonia water to make the pH of the base solution 10.8;

[0080] (3) preparing a 32% NaOH solution and an 18% ammonia solution, and mixing the NaOH and ammonia solution in a volume ratio of 8:3 to obtain a mixed alkali solution;

[0081] (4) dissolving Zr(SO4)2 in water to obtain a zirconium source solution with a concentration of 1 g / L, and dissolving ammonium tungstate in water to obtain a tungsten source solution with a concentration of 0.83 g / L;

[0082] (5) The nickel-cobalt-manganese mixed solution is uniformly added to the reactor containing the bottom liquid through a metering pump at a rate of 40 L / h. At the same time, a mixed alkali solution is added to control the pH of the reaction system between 10.2 and 10.8. The temperature of the reaction system is 56°C. Stirring is turned on at a speed of 300 r / min. After the coprecipitation reaction begins, the metering pump for controlling the feed of the zirconium source solution and the metering pump for controlling the feed of the tungsten source solution are turned on. The flow rate of the zirconium source is 0.5 L / h and the flow rate of the tungsten source is 0.3 L / h. Continue the reaction to obtain a doped lithium-rich manganese-based precursor;

[0083] N2 was introduced throughout the reaction to prevent oxidation;

[0084] (6) After washing the lithium-rich manganese-based precursor, the material was dried using a centrifuge and placed in a hot air circulation drying oven at a drying temperature of 110° C. After drying, the material was sieved to obtain a lithium-rich manganese-based precursor.

[0085] The lithium-rich manganese-based precursor prepared in this embodiment is an element-doped nickel-cobalt-manganese hydroxide, wherein 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;

[0086] Based on the total mass of the lithium-rich manganese-based precursor, the doping amount of the Zr element is 2000 ppm, the doping amount of the W element is 1000 ppm, and the molar ratio of Zr to W is 2:1.

[0087] II. Preparation of lithium-rich manganese-based positive electrode materials:

[0088] (1) grinding and sieving lithium carbonate, and then uniformly mixing it with the above-mentioned lithium-rich manganese-based precursor to obtain a mixture;

[0089] The molar ratio of Li to the metal element in the lithium-rich manganese-based precursor is 1.05:1.

[0090] (2) The mixture is placed in a roller kiln, first heated to 50°C and kept warm for 8 hours, then continued to heat to 1000°C and kept warm for 24 hours, and then slowly cooled to obtain a lithium-rich manganese-based positive electrode material, which is recorded as the positive electrode material matrix;

[0091] (3) Al2O3 and La(PO3)3 were ground into nano-scale powders in a ball mill, with the amount of Al2O3 added accounting for 0.2% of the mass of the positive electrode material matrix, and the amount of La(PO3)3 added accounting for 0.1% of the mass of the positive electrode material matrix. After the positive electrode material matrix and the ground Al2O3 and La(PO3)3 were fully mixed in the ball mill, the materials were placed in a roller kiln and heat treated at 1000°C for 10 hours in an air atmosphere to obtain a lithium-rich manganese-based positive electrode material with a coating layer.

[0092] The lithium-rich manganese-based positive electrode material prepared in this embodiment is doped with Zr and W, and the surface of the lithium-rich manganese-based positive electrode material is coated with a coating layer.

[0093] Example 2

[0094] Ⅰ. Preparation of lithium-rich manganese-based precursor:

[0095] A method for preparing a lithium-rich manganese-based precursor comprises the following steps:

[0096] (1) preparing a nickel-cobalt-manganese mixed solution: dissolving manganese sulfate, nickel sulfate, and cobalt sulfate in water at a molar ratio of Mn:Ni:Co = 6:2:2 to obtain a nickel-cobalt-manganese mixed solution;

[0097] (2) Preparation of the base solution: Add 600 L of pure water to the reactor, and then add ammonia water to make the pH of the base solution 10.5;

[0098] (3) preparing a 30% NaOH solution and an 18% ammonia solution, and mixing the NaOH and ammonia solution in a volume ratio of 9:3 to obtain a mixed alkali solution;

[0099] (4) dissolving Zr(SO4)2 in water to obtain a zirconium source solution with a concentration of 2 g / L, and dissolving ammonium tungstate in water to obtain a tungsten source solution with a concentration of 1 g / L;

[0100] (5) adding the nickel-cobalt-manganese mixed solution to the reactor containing the bottom liquid at a uniform speed of 60 L / h through a metering pump, and simultaneously adding a mixed alkali solution to control the pH of the reaction system to 10.5, the temperature of the reaction system to 50°C, turning on the stirring, the speed to 400 r / min, after the coprecipitation reaction starts, turning on the metering pump for controlling the feed of the zirconium source solution and the metering pump for controlling the feed of the tungsten source solution, the flow rate of the zirconium source is 0.4 L / h, the flow rate of the tungsten source is 0.48 L / h, and the reaction is continued to obtain a doped lithium-rich manganese-based precursor;

[0101] N2 was introduced throughout the reaction to prevent oxidation;

[0102] (6) After washing the lithium-rich manganese-based precursor, the material is dried using a centrifuge and placed in a hot air circulation drying oven at a drying temperature of 100° C. After drying, the material is sieved to obtain a lithium-rich manganese-based precursor.

[0103] The lithium-rich manganese-based precursor prepared in this embodiment is an element-doped nickel-cobalt-manganese hydroxide, wherein 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;

[0104] Based on the total mass of the lithium-rich manganese-based precursor, the doping amount of the Zr element is 2500 ppm, the doping amount of the W element is 1500 ppm, and the molar ratio of Zr to W is 1.67:1.

[0105] II. Preparation of lithium-rich manganese-based positive electrode materials:

[0106] (1) grinding and sieving lithium carbonate, and then uniformly mixing it with the above-mentioned lithium-rich manganese-based precursor to obtain a mixture;

[0107] The molar ratio of Li to the metal element in the lithium-rich manganese-based precursor is 1.03:1.

[0108] (2) The mixture was placed in a roller kiln, first heated to 60°C and kept warm for 7 hours, then continued to heat to 1050°C and kept warm for 22 hours, and then slowly cooled to obtain a lithium-rich manganese-based positive electrode material, which was recorded as the positive electrode material matrix;

[0109] (3) Al2O3 and La(PO3)3 were ground into nano-scale powders in a ball mill, with the amount of Al2O3 added accounting for 0.3% of the mass of the positive electrode material matrix, and the amount of La(PO3)3 added accounting for 0.3% of the mass of the positive electrode material matrix. After the positive electrode material matrix and the ground Al2O3 and La(PO3)3 were fully mixed in the ball mill, the materials were placed in a roller kiln and heat-treated at 900°C for 12 hours in an air atmosphere to obtain a lithium-rich manganese-based positive electrode material with a coating layer.

[0110] The lithium-rich manganese-based positive electrode material prepared in this embodiment is doped with Zr and W, and the surface of the lithium-rich manganese-based positive electrode material is coated with a coating layer.

[0111] Example 3

[0112] Ⅰ. Preparation of lithium-rich manganese-based precursor:

[0113] A method for preparing a lithium-rich manganese-based precursor comprises the following steps:

[0114] (1) preparing a nickel-cobalt-manganese mixed solution: dissolving manganese sulfate, nickel sulfate, and cobalt sulfate in water at a molar ratio of Mn:Ni:Co = 6:2:2 to obtain a nickel-cobalt-manganese mixed solution;

[0115] (2) Preparation of base solution: Add 600 L of pure water to the reactor, and then add ammonia water to make the pH of the base solution 10.2;

[0116] (3) preparing a 28% NaOH solution and a 20% ammonia solution, and mixing the NaOH and ammonia solution in a volume ratio of 2:1 to obtain a mixed alkali solution;

[0117] (4) dissolving Zr(SO4)2 in water to obtain a zirconium source solution with a concentration of 2.5 g / L, and dissolving ammonium tungstate in water to obtain a tungsten source solution with a concentration of 2 g / L;

[0118] (5) adding the nickel-cobalt-manganese mixed solution to the reactor containing the bottom liquid at a uniform speed of 40 L / min through a metering pump, and simultaneously adding a mixed alkali solution to control the pH of the reaction system to 10.2, the temperature of the reaction system to 60°C, turning on the stirring, the speed to 250 r / min, after the coprecipitation reaction starts, turning on the metering pump for controlling the feed of the zirconium source solution and the metering pump for controlling the feed of the tungsten source solution, the flow rate of the zirconium source is 1 L / h, and the flow rate of the tungsten source is 0.56 L / h, and the reaction is continued to obtain a doped lithium-rich manganese-based precursor;

[0119] N2 was introduced throughout the reaction to prevent oxidation;

[0120] (6) After washing the lithium-rich manganese-based precursor, the material is dried using a centrifuge and placed in a hot air circulation drying oven at a drying temperature of 95° C. After drying, the material is sieved to obtain a lithium-rich manganese-based precursor.

[0121] The lithium-rich manganese-based precursor prepared in this embodiment is an element-doped nickel-cobalt-manganese hydroxide, wherein 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;

[0122] Based on the total mass of the lithium-rich manganese-based precursor, the doping amount of the Zr element is 1800 ppm, the doping amount of the W element is 800 ppm, and the molar ratio of Zr to W is 2.25:1.

[0123] II. Preparation of lithium-rich manganese-based positive electrode materials:

[0124] (1) grinding and sieving lithium carbonate, and then uniformly mixing it with the above-mentioned lithium-rich manganese-based precursor to obtain a mixture;

[0125] The molar ratio of Li to the metal element in the lithium-rich manganese-based precursor is 1.06:1.

[0126] (2) The mixture is placed in a roller kiln, first heated to 70°C and kept warm for 6 hours, then continued to heat to 900°C and kept warm for 25 hours, and then slowly cooled to obtain a lithium-rich manganese-based positive electrode material, which is recorded as the positive electrode material matrix;

[0127] (3) Al2O3 and La(PO3)3 were ground into nano-scale powders in a ball mill, with the amount of Al2O3 added accounting for 0.2% of the mass of the positive electrode material matrix, and the amount of La(PO3)3 added accounting for 0.4% of the mass of the positive electrode material matrix. After the positive electrode material matrix and the ground Al2O3 and La(PO3)3 were fully mixed in the ball mill, the materials were placed in a roller kiln and heat treated at 1100°C for 8 hours in an air atmosphere to obtain a lithium-rich manganese-based positive electrode material with a coating layer.

[0128] The lithium-rich manganese-based positive electrode material prepared in this embodiment is doped with Zr and W, and the surface of the lithium-rich manganese-based positive electrode material is coated with a coating layer.

[0129] Example 4

[0130] I. A lithium-rich manganese-based precursor and a preparation method thereof. The preparation method of the lithium-rich manganese-based precursor differs from that of Example 1 only in that a chromium sulfate solution is prepared. In step (5), the chromium sulfate solution and the nickel-cobalt-manganese mixed solution are added to the reactor in parallel. The doping elements in the lithium-rich manganese-based precursor prepared in this example include Zr, W, and Cr, with the doping amount of Zr being 2000 ppm, the doping amount of W being 1000 ppm, and the doping amount of Cr being 1000 ppm.

[0131] II. A lithium-rich manganese-based positive electrode material and a preparation method thereof. The preparation method of the lithium-rich manganese-based positive electrode material differs from that of Example 1 only in that the lithium-rich manganese-based precursor of this embodiment is used to replace the lithium-rich manganese-based precursor of Example 1.

[0132] Example 5

[0133] Ⅰ. A lithium-rich manganese-based precursor and a preparation method thereof. The difference from Example 1 is that the feed rate of the zirconium source solution in the preparation method is changed so that the doping amount of the Zr element in the lithium-rich manganese-based precursor is 900 ppm. At this time, the molar ratio of Zr to W is 0.9:1.

[0134] II. A lithium-rich manganese-based positive electrode material and a preparation method thereof. The preparation method of the lithium-rich manganese-based positive electrode material differs from that of Example 1 only in that the lithium-rich manganese-based precursor of this embodiment is used to replace the lithium-rich manganese-based precursor of Example 1.

[0135] Example 6

[0136] Ⅰ. A lithium-rich manganese-based precursor and a preparation method thereof, 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 the Zr element in the lithium-rich manganese-based precursor is 3200 ppm. At this time, the molar ratio of Zr to W is 3.2:1.

[0137] II. A lithium-rich manganese-based positive electrode material and a preparation method thereof. The preparation method of the lithium-rich manganese-based positive electrode material differs from that of Example 1 only in that the lithium-rich manganese-based precursor of this embodiment is used to replace the lithium-rich manganese-based precursor of Example 1.

[0138] Example 7

[0139] Ⅰ. A lithium-rich manganese-based precursor and a preparation method thereof, 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 the W element in the lithium-rich manganese-based precursor is 600 ppm. At this time, the molar ratio of Zr to W is 3.34:1.

[0140] II. A lithium-rich manganese-based positive electrode material and a preparation method thereof. The preparation method of the lithium-rich manganese-based positive electrode material differs from that of Example 1 only in that the lithium-rich manganese-based precursor of this embodiment is used to replace the lithium-rich manganese-based precursor of Example 1.

[0141] Example 8

[0142] Ⅰ. A lithium-rich manganese-based precursor and a preparation method thereof, 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 the W element in the lithium-rich manganese-based precursor is 1600 pm. At this time, the molar ratio of Zr to W is 1.25:1.

[0143] II. A lithium-rich manganese-based positive electrode material and a preparation method thereof. The preparation method of the lithium-rich manganese-based positive electrode material differs from that of Example 1 only in that the lithium-rich manganese-based precursor of this embodiment is used to replace the lithium-rich manganese-based precursor of Example 1.

[0144] Example 9

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

[0146] II. A lithium-rich manganese-based positive electrode material and a preparation method thereof. The preparation method of the lithium-rich manganese-based positive electrode material differs from that of Example 1 in that, after step (2) and before step (3), the following operations are performed:

[0147] The lithium-rich manganese-based positive electrode material and NH4HCO3 are mixed in a mass ratio of 10:1, and the mixture is heated to 850°C to decompose NH4HCO3 into CO2 and NH3, which react with the lithium-rich manganese-based positive electrode material. A lithium-rich manganese-based positive electrode material with a spinel structure is epitaxially formed on the particle surface of the lithium-rich manganese-based positive electrode material as a modified layer. Accordingly, the lithium-rich manganese-based positive electrode material with the modified layer is used to replace the lithium-rich manganese-based positive electrode material in step (3).

[0148] Example 10

[0149] Ⅰ. A lithium-rich manganese-based precursor and its preparation method are the same as those in Example 1.

[0150] II. A lithium-rich manganese-based positive electrode material and a preparation method thereof. The preparation method of the lithium-rich manganese-based positive electrode material differs from that of Example 1 in that La(PO3)3 is replaced with an equal mass of Al2O3. The coating layer of the lithium-rich manganese-based positive electrode material prepared in this example is an aluminum oxide coating layer.

[0151] Comparative Example 1

[0152] Ⅰ. A lithium-rich manganese-based precursor and a preparation method thereof, which differs from Example 1 only in that no zirconium source solution is added in the preparation method, so that the lithium-rich manganese-based precursor does not contain Zr.

[0153] II. A lithium-rich manganese-based positive electrode material and a preparation method thereof. The preparation method of the lithium-rich manganese-based positive electrode material is different from that of Example 1 only in that the lithium-rich manganese-based precursor of this comparative example is used to replace the lithium-rich manganese-based precursor of Example 1.

[0154] Comparative Example 2

[0155] Ⅰ. A lithium-rich manganese-based precursor and a preparation method thereof, which differs from Example 1 only in 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.

[0156] II. A lithium-rich manganese-based positive electrode material and a preparation method thereof. The preparation method of the lithium-rich manganese-based positive electrode material is different from that of Example 1 only in that the lithium-rich manganese-based precursor of this comparative example is used to replace the lithium-rich manganese-based precursor of Example 1.

[0157] Battery Assembly:

[0158] The lithium-rich manganese-based positive electrode materials of Examples 1-7 and Comparative Examples 1-3 were used to prepare positive electrodes, and batteries were assembled. Specifically:

[0159] The positive electrode materials obtained in the examples and comparative examples were used to prepare button batteries. The specific preparation method was as follows: a slurry was applied at a ratio of 90 (main material): 5 (polyvinylidene fluoride PVDF): 5 (conductive agent acetylene black) to form a pole piece, a metal lithium sheet was used as a counter electrode, the diaphragm model was Celgard 2500, and a 1 mol / L lithium hexafluorophosphate solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) (the volume ratio of EC to DMC was 1:1) was used as the electrolyte. CR2032 button batteries were assembled in an argon glove box (wherein water <0.01 ppm and oxygen <0.01 ppm). Finally, the batteries were placed in a blue electric test system for electrical performance testing.

[0160] The electrical performance test conditions are as follows: charge and discharge voltage range 2.0V-4.8V, test temperature 25°C, 0.1C / 0.1C cycle for 1 week to test the initial charge and discharge capacity of the battery, and use this to calculate the first efficiency, and 1C / 1C cycle for 50 weeks to test the cycle performance of the battery. The results are shown in Table 1 below.

[0161] Table 1

[0162] As shown in Table 1, the present application co-doped nickel-cobalt-manganese hydroxide with zirconium and tungsten, resulting in a lithium-rich manganese-based cathode material prepared using the lithium-rich manganese-based precursor having a high initial efficiency and excellent cycle performance. Comparative Example 1 only doped with tungsten, and Comparative Example 2 only doped with zirconium, both of which resulted in a negligible improvement in electrochemical performance.

[0163] By comparing Example 1 with Example 4, it can be seen that further chromium doping on this basis can further improve its electrochemical performance.

[0164] By comparing Example 1 with Examples 5-6, it can be seen that Zr doping substitution can produce a "pinning effect" and a "columnar effect" by stabilizing the layered structure, promoting the Li + The diffusion of zirconium increases the electronic and ionic conductivity of the lithium-rich manganese-based positive electrode material. The doping amount of zirconium is in the preferred range of 1000-3000ppm, which can better improve the electrochemical performance of the material.

[0165] By comparing Example 1 with Examples 7-8, it can be seen that the incorporation of W can form a strong covalent bond with O, thereby stabilizing the lattice structure. The doping amount of tungsten is preferably within the range of 700ppm-1500ppm, which can better improve the electrochemical properties of its lithium-rich layered oxide.

[0166] By comparing Example 1 with Example 9, it can be seen that by setting a modified layer, Li + The migration of Li + The migration path of the material can comprehensively improve the kinetic properties and thermodynamic stability of the material.

[0167] By comparing Example 1 and Example 10, it can be seen that using oxide and phosphate as raw materials for co-coating is beneficial to increasing the energy barrier for oxygen release of the lithium-rich manganese-based positive electrode material compared to only oxide coating, thereby stabilizing the surface oxygen of the lithium-rich manganese-based positive electrode material, thereby improving the electrochemical performance, especially the cycle performance.

[0168] The applicant declares that while the above-mentioned embodiments are used to illustrate the detailed methods of the present application, the present application is not limited to the above-mentioned detailed methods, which does not mean that the present application must rely on the above-mentioned detailed methods in order to be implemented. Those skilled in the art should understand that any improvements to the present application, equivalent replacements for the raw materials of the present application's products, addition of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present application.

Claims

1. A lithium-rich manganese-based precursor, which is an element-doped nickel-cobalt-manganese hydroxide, wherein the doping elements in the lithium-rich manganese-based precursor include Zr and W.

2. The lithium-rich manganese-based precursor according to claim 1, wherein In the lithium-rich manganese-based precursor, the molar ratio of manganese, nickel and cobalt is x:y:z, wherein x>0.5, 0.4>y>0.01, 0.4>z>0.01, and x+y+z<1; Optionally, based on the total mass of the lithium-rich manganese-based precursor, the doping amount of the Zr element is 1000ppm-3000ppm; Optionally, based on the total mass of the lithium-rich manganese-based precursor, the doping amount of the W element is 700ppm-1500ppm; Optionally, the molar ratio of Zr to W is (1.5-3):1; Optionally, the doping element further includes Cr; Optionally, the ratio of the total molar amount of Zr and W to the molar amount of Cr is (1.5-4):

1.

3. The lithium-rich manganese-based precursor according to claim 1 or 2, wherein: The particle size of the lithium-rich manganese-based precursor is 5 μm-10 μm.

4. A method for preparing a lithium-rich manganese-based precursor according to any one of claims 1 to 3, comprising the following steps: Prepare nickel-cobalt-manganese mixed solution, base solution, precipitant solution, complexing agent solution, zirconium source solution and tungsten source solution; The nickel-cobalt-manganese mixed solution, the precipitant solution and the complexing agent solution are added to a reaction container containing a base solution, the temperature and pH of the reaction system are controlled to preset values, and after the coprecipitation reaction starts, the zirconium source solution and the tungsten source solution are added, and the reaction is continued to obtain a lithium-rich manganese-based precursor.

5. The method for preparing a lithium-rich manganese-based precursor according to claim 4, wherein: The addition rate of the nickel-cobalt-manganese mixed solution is 10L / h-100L / h; Optionally, the zirconium source in the zirconium source solution includes Zr(SO4)2, CH4NO3Zr and Zr(O2CCH3)4 At least one of; Optionally, the concentration of the zirconium source solution is 0.1 g / L-3 g / L; Optionally, the flow rate of the zirconium source solution is 0.3L / h-3L / h; Optionally, the tungsten source in the tungsten source solution includes at least one of ammonium tungstate and Na2WO4; Optionally, the concentration of the tungsten source solution is 0.1 g / L-3 g / L; Optionally, the flow rate of the tungsten source solution is 0.3L / h-3L / h; Optionally, the preparation method further comprises: preparing a chromium source solution, and adding the chromium source solution and the nickel-cobalt-manganese mixed solution into a container in parallel to perform chromium doping; Optionally, the preset value of the temperature is 40°C-65°C, and the preset value of the pH is 9.5-11.5; Optionally, after controlling the temperature and pH of the reaction system to preset values, stirring is started, and the zirconium source solution and the tungsten source solution are added under stirring, and the stirring speed is 200r / min-400r / min.

6. A lithium-rich manganese-based positive electrode material prepared using the lithium-rich manganese-based precursor according to any one of claims 1 to 3, wherein Zr and W are doped; Optionally, the lithium-rich manganese-based positive electrode material is also doped with Cr; Optionally, a coating layer is provided on the surface of the lithium-rich manganese-based positive electrode material, and raw materials for preparing the coating layer include oxides and phosphates; Optionally, the oxide includes at least one of Al2O3, ZrO2 and MnO2; Optionally, the phosphate comprises a rare earth phosphate; Optionally, the phosphate includes at least one of La(PO3)3, PrPO4 and Ca3(PO4)2; Optionally, a modified layer is further provided between the surface of the lithium-rich manganese-based positive electrode material and the coating layer, and the modified layer is a lithium-rich manganese-based positive electrode material with a spinel structure obtained by reacting the lithium-rich manganese-based positive electrode material with NH3 and CO2.

7. A method for preparing the lithium-rich manganese-based positive electrode material as claimed in claim 6, comprising the following steps: (1) After mixing the lithium salt and the lithium-rich manganese-based precursor, calcining at high temperature, the lithium-rich manganese-based positive electrode material is obtained, which is referred to as the positive electrode material matrix.

8. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 7, wherein: The lithium salt includes at least one of lithium carbonate and lithium hydroxide; Optionally, the lithium salt is ground and sieved before use; Optionally, the high temperature calcination includes: first heating to 50°C-80°C and keeping the temperature for 6h-10h, and then heating to 850°C-1100°C and keeping the temperature for 20h-26h.

9. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 7 or 8, wherein: The preparation method further comprises step (2): The cathode material matrix 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; Optionally, the oxide is ground before use; Optionally, the mass of the oxide accounts for 0.1%-0.5% of the mass of the positive electrode material matrix; Optionally, the phosphate is ground before use; Optionally, the mass of the phosphate accounts for 0.1%-0.5% of the mass of the positive electrode material matrix; Optionally, the temperature of the heat treatment is 900°C-1100°C, and the time of the heat treatment is 8h-12h; Optionally, the preparation method further comprises, after step (1) and before step (2), performing a modification treatment on the positive electrode material matrix, and the modification treatment method comprises the following steps: The positive electrode material matrix and NH4HCO3 are mixed, and the NH4HCO3 is heated to decompose CO2 and NH3, and react with the positive electrode material matrix to epitaxially form a spinel-structured lithium-manganese-based positive electrode material as a modified layer on the particle surface of the positive electrode material matrix; Optionally, the mass ratio of the lithium-rich manganese-based positive electrode material to NH4HCO3 is 10:(0.5-3); Optionally, the heating temperature is 600°C-1000°C.

10. A lithium-ion battery comprising the lithium-rich manganese-based positive electrode material according to claim 6.

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