High-entropy lithium-rich manganese-based precursor, and preparation method therefor and use thereof

Abstract

Disclosed in the present application are a high-entropy lithium-rich manganese-based precursor, and a preparation method therefor and the use thereof. The preparation method comprises the following steps: 1) preparing an aluminum-niobium co-doped nickel-manganese precursor by using a co-precipitation method; 2) introducing a doping and coating solution into the reaction system for preparing the aluminum-niobium co-doped nickel-manganese precursor, wherein the doping and coating solution comprises zirconium, tungsten and titanium, proceeding with the co-precipitation reaction to coat the aluminum-niobium co-doped nickel-manganese precursor, thereby obtaining a doped and coated precursor; and 3) sintering the doped and coated precursor to make doping elements in the doped and coated precursor diffuse, thereby obtaining the high-entropy lithium-rich manganese-based precursor. In the present application, by combining wet doping and coating in a synthesis stage of the high-entropy lithium-rich manganese-based precursor, elements are uniformly distributed without affecting the morphology and structure of the precursor, thereby effectively improving the structural stability of the high-entropy lithium-rich manganese-based positive electrode material prepared from the precursor, and improving the electrochemical performance thereof.

Description

High-entropy lithium-rich manganese-based precursor, preparation method and application thereof TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries and relates to a high-entropy lithium-rich manganese-based precursor, a preparation method and application thereof. BACKGROUND

[0002] The lithium-rich manganese-based material is a representative material of the next generation of low-cost and high-energy-density lithium ion battery cathode materials. However, at present, although the lithium-rich manganese-based material has obvious specific capacity advantages and great potential, it still has problems such as low first discharge efficiency, poor rate performance and voltage decay due to slow technical progress, and it still needs time to be put on the market in large quantities.

[0003] To solve these problems, the main solutions include coating, acid treatment, doping, pre-cycling, heat treatment and the like. For example, CN110890541A discloses a preparation method of a surface-modified lithium-rich manganese-based cathode material, which comprises the following steps: 1) uniformly mixing an original lithium-rich manganese-based cathode material with a fast ion conductor coating liquid, performing solid-liquid separation, and obtaining a surface-modified lithium-rich manganese-based cathode material precursor; the solute in the fast ion conductor coating liquid is selected from one or more of soluble hydrogen phosphate, pyrophosphate and meta-aluminate, and the solvent is water; 2) performing heat treatment on the obtained surface-modified lithium-rich manganese-based cathode material precursor to obtain a surface-modified lithium-rich manganese-based cathode material. The patent adopts a one-step process to achieve the dual effects of coating and water washing to reduce the total alkali content, and the process flow is simple, the conditions are mild, and the process is easy to scale up and industrialize. After modification, the total alkali content on the surface of the material is significantly reduced, and the first coulombic efficiency and rate performance are greatly improved.

[0004] The method for constructing stable lithium-rich manganese-based positive electrode material by entropy stabilization strategy can effectively promote the development of lithium-rich manganese-based material. Two process routes of high-entropy lithium-rich manganese-based material, one is wet doping in the precursor stage, for example, CN106910887B discloses a lithium-rich manganese-based positive electrode material, the chemical formula of the lithium-rich manganese-based positive electrode material is Li1+xMnyMzAwOr, wherein M is at least one of Ni, Co, Al, Mg, Ti, Fe, Cu, Cr, Mo, Zr, Ru and Sn, A is at least one of S, P, B and F, and 0

[0005] Therefore, it is an urgent technical problem to provide a high-entropy lithium-rich manganese-based precursor with high performance and a preparation method thereof. SUMMARY

[0006] 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.

[0007] In view of the above problems existing in the prior art, the purpose of the present application is to provide a high-entropy lithium-rich manganese-based precursor, a preparation method and application thereof.

[0008] To achieve the above-mentioned purpose, the following technical solutions are adopted in the present application:

[0009] In a first aspect, the present application provides a preparation method of a high-entropy lithium-rich manganese-based precursor, the preparation method comprising the following steps:

[0010] (1) using a co-precipitation method to prepare an aluminum-niobium co-doped nickel-manganese precursor;

[0011] (2) introducing a doping-coating solution into the reaction system for preparing the aluminum-niobium co-doped nickel-manganese precursor, the doping-coating solution comprising zirconium, tungsten and titanium, and continuing the co-precipitation reaction to coat the aluminum-niobium co-doped nickel-manganese precursor, to obtain a doped-coated precursor;

[0012] (3) sintering the doped-coated precursor to diffuse the doping elements in the doped-coated precursor, to obtain the high-entropy lithium-rich manganese-based precursor.

[0013] By combining wet doping and coating in the synthesis stage of the high-entropy lithium-rich manganese-based precursor, the present application can avoid segregation of the doping elements and does not affect the morphology and structure of the precursor, can effectively improve the structural stability of the high-entropy lithium-rich manganese-based positive electrode material prepared by using the precursor, and improve the electrochemical performance. Specifically, the Al and Nb elements which are easier to dope are directly doped by using the co-precipitation method, and the Ti element, the Zr element and the W element which are not easy to dope are uniformly coated by using the wet method, and the coated elements are diffused into the interior of the precursor by using sintering in the later stage, to realize gradient doping, which can effectively improve the stability of the material, thereby reducing the voltage attenuation and improving the cycle performance.

[0014] The following is an optional technical solution of the present application, but is not a limitation on the technical solutions provided by the present application. Through the following optional technical solution, the technical purpose and beneficial effects of the present application can be better achieved and realized.

[0015] In one embodiment, step (1) comprises: adding a mixed solution A containing nickel, manganese, aluminum and niobium, a precipitant solution and a complexing agent solution into a reaction kettle in parallel flow, to perform a co-precipitation reaction, to obtain an aluminum-niobium co-doped nickel-manganese precursor.

[0016] In one embodiment, the total metal concentration in the mixed solution A is 1 mol / L-3 mol / L, for example, it can be 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.3 mol / L, 2.6 mol / L, 2.8 mol / L or 3 mol / L, etc.

[0017] In one embodiment, the precipitant solution is liquid alkali, and the concentration of the liquid alkali is 8 mol / L-12 mol / L, for example, it can be 8 mol / L, 8.2 mol / L, 8.5 mol / L, 9 mol / L, 9.5 mol / L, 10 mol / L, 10.5 mol / L, 11 mol / L, 11.5 mol / L or 12 mol / L, etc.

[0018] In an embodiment, the complexing agent solution is ammonia water, and the concentration of the ammonia water is 5 mol / L-8 mol / L, for example, it can be 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L or 8 mol / L, etc. The use of very low complexing agent concentration in the synthesis of niobium-aluminum doped precursor reaction process forms a loose porous structure, which is beneficial to lithium ion diffusion and improves the rate performance of the material.

[0019] In an embodiment, the pH of the coprecipitation reaction in step (1) is 9.0-9.5, for example, it can be 9.0, 9.1, 9.2, 9.3, 9.4 or 9.5, etc.

[0020] In an embodiment, the ammonia concentration of the reaction system during the coprecipitation reaction in step (1) is 1 g / L-2 g / L, for example, it can be 1 g / L, 1.2 g / L, 1.3 g / L, 1.4 g / L, 1.5 g / L, 1.7 g / L, 1.8 g / L or 2 g / L, etc.

[0021] In an embodiment, the temperature of the coprecipitation reaction in step (1) is 40℃-50℃, for example, it can be 40℃, 42℃, 44℃, 45℃, 47℃, 48℃ or 50℃, etc.

[0022] In an embodiment, the coprecipitation reaction in step (1) is accompanied by stirring, and the stirring speed is 300 rpm-500 rpm, for example, it can be 300 rpm, 320 rpm, 330 rpm, 340 rpm, 360 rpm, 380 rpm, 400 rpm, 420 rpm, 440 rpm, 460 rpm, 480 rpm or 500 rpm, etc.

[0023] In an embodiment, the D50 of the aluminum-niobium co-doped nickel-manganese precursor in step (1) is 3 μm-18 μm, for example, it can be 3 μm, 5 μm, 7 μm, 8 μm, 10 μm, 12 μm, 13 μm, 15 μm, 16 μm or 18 μm, etc.

[0024] As an optional technical solution of the preparation method of the high-entropy lithium-rich manganese-based precursor described in the present application, the doping coating solution in step (2) comprises a zirconium-titanium mixed solution B and a sodium tungstate solution C, which are introduced into the reaction system in a parallel flow manner.

[0025] In one embodiment, the zirconium-titanium mixed solution B is adjusted to a pH of 0.5-1 before use, for example, it can be 0.5, 0.6, 0.7, 0.8, 0.9 or 1, etc. By adjusting the pH, on the one hand, it can inhibit the hydrolysis of zirconium ions and titanium ions to form precipitates, form a stable solution, avoid the entry of solid impurities in the solution into the reaction system to form new crystal nuclei, thereby stabilizing the reaction conditions of the precursor, making the grain growth of the precursor more stable and more consistent; on the other hand, it can avoid the preferential precipitation of zirconium ions and titanium ions in the raw materials, thereby reducing the doping amount in the material. The reagent used to adjust the pH can be dilute sulfuric acid.

[0026] The present application utilizes the characteristics that titanium ions and zirconium ions hydrolyze to form precipitates under slightly higher pH conditions, the sodium tungstate solution is alkaline, and the tungsten element precipitates under acidic conditions. In the coating stage, no precipitant and complexing agent is needed, and the two solutions are mixed directly to naturally form precipitates and coat the aluminum-niobium co-doped nickel-manganese precursor.

[0027] In one embodiment, the total metal concentration in the zirconium-titanium mixed solution B is 0.003 mol / L-0.01 mol / L, for example, it can be 0.003 mol / L, 0.004 mol / L, 0.006 mol / L, 0.008 mol / L or 0.01 mol / L, etc.

[0028] In one embodiment, the concentration of the sodium tungstate solution C is 0.003 mol / L-0.01 mol / L, for example, it can be 0.003 mol / L, 0.004 mol / L, 0.006 mol / L, 0.008 mol / L or 0.01 mol / L, etc. In one embodiment, the temperature of the co-precipitation reaction in step (2) is 40℃-50℃, for example, it can be 40℃, 42℃, 43℃, 45℃, 47℃ or 50℃, etc.

[0029] In one embodiment, the time of the co-precipitation reaction in step (2) is 10h-20h, for example, it can be 10h, 12h, 13h, 14h, 15h, 16h, 18h or 20h, etc.

[0030] In one embodiment, the atmosphere of the sintering in step (3) is an oxygen-containing atmosphere.

[0031] In one embodiment, the temperature of the sintering in step (3) is 500℃-600℃, for example, it can be 500℃, 520℃, 540℃, 550℃, 565℃, 570℃, 580℃, 590℃ or 600℃, etc.

[0032] In one embodiment, the sintering time of step (3) is 4h-6h, for example, it can be 4h, 4.2h, 4.5h, 4.7h, 5h, 5.5h or 6h, etc.

[0033] In a second aspect, the present application provides a high-entropy lithium-rich manganese-based precursor, which is prepared by the method of the first aspect. The high-entropy lithium-rich manganese-based precursor has pores on the surface and inside.

[0034] In one embodiment, the chemical formula of the high-entropy lithium-rich manganese-based precursor is Ni x Mn y Al a Zr b W c Ti d Nb e (OH)2, wherein 0.3≤x≤0.4, 0.6≤y≤0.7, 0.001≤a≤0.01, 0.001≤b≤0.003, 0.001≤c≤0.003, 0.001≤d≤0.003, 0.003≤e≤0.01, and x+y+a+b+c+d+e=1. For example, x can be 0.3, 0.32, 0.35, 0.36, 0.38 or 0.4, etc.; y can be 0.6, 0.62, 0.63, 0.66, 0.68 or 0.7, etc.; a can be 0.001, 0.003, 0.005, 0.007, 0.008 or 0.01, etc.; b can be 0.001, 0.002 or 0.003, etc.; c can be 0.001, 0.002 or 0.003, etc.; d can be 0.001, 0.002 or 0.003, etc.; and e can be 0.003, 0.005, 0.006, 0.007, 0.008, 0.009 or 0.01, etc.

[0035] In a third aspect, the present application provides a high-entropy lithium-rich manganese-based positive electrode material, which is prepared by using the high-entropy lithium-rich manganese-based precursor of the second aspect.

[0036] In a fourth aspect, the present application provides a preparation method of the high-entropy lithium-rich manganese-based positive electrode material of the third aspect, which comprises the following steps:

[0037] The lithium source and the high-entropy lithium-rich manganese-based precursor are mixed at a molar ratio of lithium to metal in the high-entropy lithium-rich manganese-based precursor of 1.22-1.28, and then sintered in an oxygen-containing atmosphere to obtain the high-entropy lithium-rich manganese-based positive electrode material.

[0038] In the technical solution, the molar ratio of lithium to the metals in the high-entropy lithium-rich manganese-based precursor is 1.22-1.28, for example, it can be 1.22, 1.23, 1.24, 1.25, 1.26, 1.27 or 1.28, etc.

[0039] In one embodiment, in the preparation of the high-entropy lithium-rich manganese-based material, the sintering temperature is 800-900℃, for example, it can be 800℃, 820℃, 840℃, 850℃, 860℃, 870℃, 880℃ or 900℃, etc.; the sintering time is 10-20h, for example, it can be 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h or 20h, etc.

[0040] In a fifth aspect, the application provides a lithium ion battery, wherein the lithium ion battery comprises the high-entropy lithium-rich manganese-based positive electrode material of the third aspect.

[0041] The numerical ranges described in the present application include not only the point values listed above, but also any point values between the above-listed numerical ranges, and the specific point values included in the ranges are not listed in the present application due to the length and the consideration of simplicity.

[0042] Compared with the prior art, the application has the following beneficial effects:

[0043] In the synthesis stage of the high-entropy lithium-rich manganese-based precursor, the present application combines wet doping with coating to avoid segregation of the doping elements and not affect the morphology and structure of the precursor. Specifically, the Al and Nb elements which are easier to dope are directly wet-doped by the coprecipitation method, while the Ti element, the Zr element and the W element which are not easy to dope are uniformly coated by wet method, and the coated elements are diffused into the interior of the precursor by sintering in the later stage, realizing gradient doping, which can effectively improve the stability of the material, thereby reducing the voltage attenuation and improving the cycle performance.

[0044] Other aspects can be apparent after reading and understanding the drawings and detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0045] The accompanying drawings are used to provide a further understanding of the technical solutions of the present application, and constitute a part of the specification, together with the embodiments of the present application, to explain the technical solutions of the present application, and do not constitute a limitation on the technical solutions of the present application.

[0046] Fig. 1 and Fig. 2 are scanning graphs of the high-entropy lithium-rich manganese-based precursor prepared in Example 1 under different rates. DETAILED DESCRIPTION

[0047] The technical solutions of the present application will be further described below in combination with the drawings and through specific embodiments.

[0048] The specific embodiments described herein merely illustrate the application and are not intended to limit the application.

[0049] In the embodiments of the application, the lithium ratio refers to the molar ratio of lithium element to metal elements in the precursor.

[0050] Embodiment 1

[0051] The embodiment provides a preparation method of a high-entropy lithium-rich manganese-based precursor, and comprises the following steps:

[0052] Step 1: a nickel-manganese-aluminum-niobium mixed solution A with a total metal concentration of 2 mol / L is prepared according to the molar ratio of Ni:Co:Al:Nb = 32:67:0.5:0.5;

[0053] A mixed solution B of titanyl sulfate and zirconium sulfate with a total metal concentration of 0.005 mol / L is prepared according to the molar ratio of Ti:Zr = 1:1, and the pH of the solution is adjusted to 0.8 by dilute sulfuric acid to inhibit the dissolution of titanium ions and zirconium ions;

[0054] A sodium tungstate solution C with a concentration of 0.005 mol / L is prepared;

[0055] 10 mol / L of liquid alkali is prepared as a precipitant, and 8 mol / L of ammonia solution is prepared as a complexing agent.

[0056] Step 2: under the protection of nitrogen, the mixed solution A, the liquid alkali and the ammonia water are added into a reaction kettle in parallel flow, the reaction pH is adjusted to 9.0, the ammonia concentration is adjusted to 1 g / L, the temperature is adjusted to 40°C, the stirring speed is adjusted to 300 rpm, and the particle size is grown to 18 μm before the feeding is stopped.

[0057] Step 3: the solution B and the solution C are added into the reaction kettle in parallel flow, the feeding is stopped after 20 h of reaction, and a doped and coated hydroxide precursor is obtained.

[0058] Step 4: the doped and coated hydroxide precursor is sintered in an air atmosphere at 600°C for 6 h, and a doped oxide precursor, that is, a high-entropy lithium-rich manganese-based precursor, is obtained.

[0059] The chemical formula of the high-entropy lithium-rich manganese-based precursor prepared in the embodiment is Ni 0.315 Mn 0.669 Al 0.005 Zr 0.0015 W 0.003 Ti 0.0015 Nb 0.005 O.

[0060] Figure 1 is an SEM photo of the high-entropy lithium-rich manganese-based precursor prepared in Example 1, and Figure 2 is a cross-sectional SEM photo of the high-entropy lithium-rich manganese-based precursor prepared in Example 1, from which it can be seen that the precursor material has high sphericity, fine primary particles, and a large number of pores on the surface and inside.

[0061] The present embodiment also provides a preparation method of a high-entropy lithium-rich manganese-based positive electrode material, comprising the following steps:

[0062] The lithium carbonate and the high-entropy lithium-rich manganese-based precursor are mixed uniformly at a lithium ratio of 1.22, sintered at 900°C for 12h in an air atmosphere, and a lithium-rich manganese-based positive electrode material is obtained.

[0063] Example 2

[0064] The present embodiment provides a preparation method of a high-entropy lithium-rich manganese-based precursor, comprising the following steps:

[0065] Step 1, a nickel-manganese-aluminum-niobium mixed solution A with a total metal concentration of 2mol / L is prepared according to a molar ratio of Ni:Co:Al:Nb = 38:61:0.3:0.7;

[0066] A mixed solution B of titanium oxysulfate and zirconium sulfate with a total metal concentration of 0.003mol / L is prepared according to a molar ratio of Ti:Zr = 1:2, and the pH of the solution is adjusted to 1 with dilute sulfuric acid to inhibit the dissolution of titanium ions and zirconium ions;

[0067] A sodium tungstate solution C with a concentration of 0.003mol / L is prepared;

[0068] A liquid alkali with a concentration of 10mol / L is prepared as a precipitant, and an ammonia solution with a concentration of 8mol / L is prepared as a complexing agent.

[0069] Step 2, under the protection of nitrogen, the mixed solution A, the liquid alkali, and the ammonia solution are added to the reaction kettle in parallel flow, the reaction pH is adjusted to 9.5, the ammonia concentration is adjusted to 2g / L, the temperature is adjusted to 45°C, the stirring speed is adjusted to 400rpm, and the particle size is grown to 10μm before stopping the feeding.

[0070] Step 3, the solution B and the solution C are added to the reaction kettle in parallel flow, the feeding is stopped after 15h of reaction, and a doped coated hydroxide precursor is obtained.

[0071] Step 4, the doped coated hydroxide precursor is sintered at 550°C in an air atmosphere for 5h, a doped oxide precursor is obtained, and a high-entropy lithium-rich manganese-based precursor is obtained.

[0072] The chemical formula of the high-entropy lithium-rich manganese-based precursor prepared in the present embodiment is Ni 0.378 Mn 0.606 Al 0.003 Zr 0.002 W 0.003Ti 0.001 Nb 0.007 O.

[0073] The embodiment also provides a preparation method of the high-entropy lithium-rich manganese-based positive electrode material, including the following steps:

[0074] Lithium hydroxide is uniformly mixed with the high-entropy lithium-rich manganese-based precursor at a lithium ratio of 1.26, and then sintered at 880 DEG C for 15 h in an oxygen atmosphere to obtain the lithium-rich manganese-based positive electrode material.

[0075] Embodiment 3

[0076] The embodiment provides a preparation method of a high-entropy lithium-rich manganese-based precursor, including the following steps:

[0077] Step 1, a mixed solution A of nickel, manganese, aluminum and niobium is prepared at a molar ratio of Ni:Co:Al:Nb=35:64:0.7:0.3, and the total metal concentration is 1.5 mol / L;

[0078] A mixed solution B of titanium oxysulfate and zirconium sulfate is prepared at a molar ratio of Ti:Zr=1:1, and the total metal concentration is 0.002 mol / L, and the pH of the solution is adjusted to 0.5 by dilute sulfuric acid to inhibit the dissolution of titanium ions and zirconium ions;

[0079] A sodium tungstate solution C with a concentration of 0.002 mol / L is prepared;

[0080] A liquid alkali with a concentration of 12 mol / L is prepared as a precipitant, and an ammonia solution with a concentration of 5 mol / L is prepared as a complexing agent.

[0081] Step 2, under the protection of nitrogen, the mixed solution A, the liquid alkali and the ammonia solution are added into a reaction kettle in parallel flow, the pH of the reaction is adjusted to 9.2, the ammonia concentration is 1.5 g / L, the temperature is 50 DEG C, the stirring speed is 500 rpm, and the feeding is stopped when the particle size grows to 8 μm.

[0082] Step 3, the solution B and the solution C are added into the reaction kettle in parallel flow, the feeding is stopped after 15 h of reaction, and a doped and coated hydroxide precursor is obtained.

[0083] Step 4, the doped and coated hydroxide precursor is sintered at 575 DEG C in an air atmosphere for 4.5 h to obtain a doped oxide precursor, that is, a high-entropy lithium-rich manganese-based precursor.

[0084] The chemical formula of the high-entropy lithium-rich manganese-based precursor prepared in the embodiment is Ni 0.347 Mn 0.657 Al 0.007 Zr 0.001 W 0.002 Ti 0.001 Nb 0.003 O.

[0085] The embodiment also provides a preparation method of the high-entropy lithium-rich manganese-based positive electrode material, including the following steps:

[0086] The lithium carbonate and the high-entropy lithium-rich manganese-based precursor are mixed uniformly according to a lithium ratio of 1.25, sintered at 840 DEG C for 18 h in an air atmosphere, and a lithium-rich manganese-based positive electrode material is obtained.

[0087] Example 4

[0088] The embodiment is different from the example 1 in that in the step 1, the pH is not adjusted by using dilute sulfuric acid.

[0089] Example 5

[0090] The embodiment is different from the example 1 in that in the step 3, the solution B and the solution C are added into the reaction kettle in a concurrent flow, and the liquid alkali and the ammonia water are also added into the reaction kettle in a concurrent flow to perform the co-precipitation reaction.

[0091] Example 6

[0092] The embodiment is different from the example 1 in that the step 4 is not performed in the preparation method of the precursor.

[0093] Comparative example 1

[0094] The embodiment is different from the example 1 in that the aluminum, the niobium, the zirconium, the tungsten and the titanium elements are doped by co-precipitation in the step 2, and the sintering of the step 4 is not performed.

[0095] Battery assembly:

[0096] The lithium-rich manganese-based positive electrode materials provided by the examples 1-6 and the comparative example 1 are weighed according to a mass ratio of 95:3:2 of the super carbon black, the polyvinylidene fluoride (PVDF) and the lithium-rich manganese-based positive electrode material, and are fully mixed, coated on an aluminum foil, and placed into a vacuum drying oven at 100 DEG C for 5 h. After being taken out, the lithium-rich manganese-based positive electrode material is placed on a rolling machine and rolled several times, and then cut into a circular piece. The circular piece is used as a positive electrode, a lithium sheet is used as a negative electrode, a polypropylene microporous membrane is used as a separator, and 1 mol / L of LiPF6+EC / DMC / EMC is used as an electrolyte. The assembly of the CR2032 stainless steel button cell is completed in an argon-filled glove box with a water content of less than 0.1 ppm. After being placed for 12 h, the charge and discharge performance of the lithium-rich manganese-based positive electrode material is tested.

[0097] Performance test:

[0098] Under the test condition of a voltage of 2.0-4.8 V and 0.1 C, the first charge and discharge are performed, and the ratio of the discharge capacity to the charge capacity is the first discharge efficiency;

[0099] Under the condition of a voltage of 2.0-4.8 V, the ratio of the discharge capacity at 8 C to the discharge capacity at 0.2 C is used to evaluate the rate performance.

[0100] The voltage attenuation was evaluated by the discharge voltage after 50 cycles and the first discharge voltage under the condition of 0.1C test at 2.0-4.8V.

[0101] The test results are shown in Table 1.

[0102] Table 1

[0103] As shown in Table 1, the stability of the material can be improved by introducing different kinds of elements in the form of wet doping and coating, and the coated elements can diffuse into the precursor by sintering, so as to effectively improve the electrochemical performance of the high-entropy lithium-rich manganese-based positive electrode material.

[0104] Meanwhile, as shown by the comparison between Example 1 and Example 4, the use of dilute sulfuric acid to adjust the pH can inhibit the precipitation of zirconium ions and titanium ions caused by hydrolysis, form a stable solution, avoid the generation of new crystal nuclei caused by the entry of solid impurities in the solution into the reaction system, and thus stabilize the reaction conditions of the precursor, make the grain growth of the precursor more stable, and have higher consistency; on the other hand, it can avoid the preferential precipitation of zirconium ions and titanium ions in the raw materials, so as to reduce the doping amount in the material. Therefore, the comprehensive performance of the material can be improved.

[0105] As shown by the comparison between Example 1 and Example 5, in a strong alkaline environment, even if a complexing agent such as ammonia is added, the precipitation speed of Zr and Ti will be too fast, the surface coating will be uneven, and W cannot form a precipitate under strong alkaline conditions, thereby affecting the final doping effect.

[0106] As shown by the comparison between Example 1 and Example 6, the elements coated on the surface can be diffused into the material by pre-sintering, while the hydroxide directly mixed with lithium and sintered will be affected by lithium elements during the diffusion process, resulting in segregation, and thus affecting the final effect.

[0107] As shown by the comparison between Example 1 and Comparative Example 1, the multi-element synergistic doping can effectively stabilize the material structure, improve the initial efficiency and rate performance, and reduce the voltage attenuation.

[0108] The applicant declares that the above examples are used to illustrate the detailed method of the application, but the application is not limited to the above detailed method, i.e. the application does not mean that the application must rely on the above detailed method to be implemented. It should be understood by those skilled in the art that any improvement of the application, equivalent replacement of each raw material of the product of the application, addition of auxiliary ingredients, selection of specific methods, etc. fall within the protection scope and disclosure scope of the application.

Claims

1. A method for preparing a high-entropy lithium-rich manganese-based precursor, comprising the following steps: (1) preparing an aluminum and niobium co-doped nickel-manganese precursor by a co-precipitation method; (2) introducing a doping coating solution into the reaction system for preparing the aluminum and niobium co-doped nickel-manganese precursor, the doping coating solution comprising zirconium, tungsten and titanium, and continuing the co-precipitation reaction to coat the aluminum and niobium co-doped nickel-manganese precursor, thereby obtaining a doped and coated precursor; (3) sintering the doped and coated precursor to diffuse the doping elements in the doped and coated precursor, thereby obtaining the high-entropy lithium-rich manganese-based precursor.

2. The method of claim 1, wherein the high-entropy lithium-rich manganese-based precursor is prepared by the steps of: Step (1) comprises: introducing a mixed solution A containing nickel, manganese, aluminum and niobium, a precipitant solution and a complexing agent solution into a reaction kettle in a concurrent manner to perform a co-precipitation reaction, thereby obtaining the aluminum and niobium co-doped nickel-manganese precursor. Optionally, the total metal concentration in the mixed solution A is 1 mol / L-3 mol / L. Optionally, the precipitant solution is liquid alkali, and the concentration of the liquid alkali is 8 mol / L-12 mol / L. Optionally, the complexing agent solution is ammonia water, and the concentration of the ammonia water is 5 mol / L-8 mol / L. Optionally, the pH of the co-precipitation reaction in step (1) is 9.0-9.

5. Optionally, during the co-precipitation reaction in step (1), the ammonia concentration of the reaction system is 1 g / L-2 g / L. Optionally, the temperature of the co-precipitation reaction in step (1) is 40℃-50℃. Optionally, the co-precipitation reaction in step (1) is accompanied by stirring, and the stirring speed is 300 rpm-500 rpm.

3. The method of producing a high-entropy lithium-rich manganese-based precursor according to claim 1 or 2, wherein, The D50 of the aluminum and niobium co-doped nickel-manganese precursor in step (1) is 3 μm-18 μm.

4. The method of making a high-entropy lithium-rich manganese-based precursor of any one of claims 1-3, wherein, The doping coating solution in step (2) comprises a zirconium and titanium mixed solution B and a sodium tungstate solution C, and the zirconium and titanium mixed solution B and the sodium tungstate solution C are introduced into the reaction system in a concurrent manner. Optionally, the zirconium and titanium mixed solution B is adjusted to a pH of 0.5-1 before use. Optionally, the total metal concentration in the zirconium and titanium mixed solution B is 0.003 mol / L-0.01 mol / L. Optionally, the concentration of the sodium tungstate solution C is 0.003 mol / L-0.01 mol / L. Optionally, the temperature of the co-precipitation reaction in step (2) is 40℃-50℃. Optionally, the time of the co-precipitation reaction in step (2) is 10 h-20 h.

5. The method of making a high-entropy lithium-rich manganese-based precursor of any one of claims 1-4, wherein, The sintering atmosphere in step (3) is an oxygen-containing atmosphere. Optionally, the temperature of the sintering in step (3) is 500℃-600℃. Optionally, the time of the sintering in step (3) is 4 h-6 h.

6. A high-entropy lithium-rich manganese-based precursor prepared by the method of any one of claims 1-5, wherein, The high-entropy lithium-rich manganese-based precursor has pores on the surface and inside. Optionally, the high-entropy lithium-rich manganese-based precursor has a chemical formula of Ni x Mn y Al a Zr b W c Ti d Nb e O, wherein 0.3≤x≤0.4, 0.6≤y≤0.7, 0.001≤a≤0.01, 0.001≤b≤0.003, 0.001≤c≤0.003, 0.001≤d≤0.003, 0.003≤e≤0.01, and x+y+a+b+c+d+e=1. 7.A high-entropy lithium-rich manganese-based positive electrode material prepared by using the high-entropy lithium-rich manganese-based precursor in claim 6.

8. A method of preparing the high-entropy lithium-rich manganese-based cathode material of claim 7, comprising the steps of: The lithium source and the high-entropy lithium-rich manganese-based precursor are mixed in a molar ratio of lithium to metal in the high-entropy lithium-rich manganese-based precursor of 1.22-1.28, and then sintered in an oxygen-containing atmosphere, thereby obtaining the high-entropy lithium-rich manganese-based positive electrode material.

9. The method for preparing the high-entropy lithium-rich manganese-based cathode material according to claim 8, wherein, The high-entropy lithium-rich manganese-based material is prepared by sintering at a temperature of 800-900 DEG C for 10-20 hours.

10. A lithium ion battery comprising the high-entropy lithium-rich manganese-based positive electrode material of claim 7.

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