阅读说明：本技术 一种偏钒酸钾分散包覆镍钴锰三元正极材料的制备方法 (Preparation method of potassium metavanadate dispersed coated nickel-cobalt-manganese ternary cathode material ) 是由 朱文婷 何磊 丁楚雄 李道聪 于 2020-02-28 设计创作，主要内容包括：本发明公开了一种偏钒酸钾分散包覆镍钴锰三元正极材料的制备方法,先将Ni、Co、Mn的硫酸盐溶液混合后在碱性条件下进行共沉淀反应制得三元复合前驱体(Ni<Sub>x</Sub>Co<Sub>y</Sub>Mn<Sub>z</Sub>)(OH)<Sub>2</Sub>,然后再用去离子水洗涤、打浆、过滤后得浆料,将锂源和偏钒酸钾加入浆料中依次进行均质细化处理、喷雾干燥和高温煅烧后得到偏钒酸钾分散包覆镍钴锰三元正极材料。本发明通过在三元正极表面包覆KVO<Sub>3</Sub>,提高了材料的表面结构稳定性,同时提高了材料的离子迁移率,从而提升三元材料的电化学性能；本发明制备的镍钴锰三元正极材料分散性好、大小均匀、球形度高、二次颗粒疏松,有利于电解液的浸润,提高了锂离子的扩散速率,从而提高倍率性能和循环性能。(The invention discloses a preparation method of a potassium metavanadate dispersed and coated nickel-cobalt-manganese ternary positive electrode material x Co y Mn z ）(OH) 2 And then washing with deionized water, pulping, filtering to obtain a slurry, adding a lithium source and potassium metavanadate into the slurry, and sequentially carrying out homogenizing and refining treatment, spray drying and high-temperature calcination to obtain the potassium metavanadate dispersed and coated nickel-cobalt-manganese ternary cathode material. The invention is realized by using a ternary anode tableSurface-coated KVO 3 The surface structure stability of the material is improved, and the ion mobility of the material is improved, so that the electrochemical performance of the ternary material is improved; the nickel-cobalt-manganese ternary cathode material prepared by the invention has the advantages of good dispersibility, uniform size, high sphericity and loose secondary particles, is beneficial to the infiltration of electrolyte, and improves the diffusion rate of lithium ions, thereby improving the rate capability and the cycle performance.)

1. A preparation method of a potassium metavanadate dispersed coated nickel-cobalt-manganese ternary cathode material is characterized by comprising the following steps of: the method specifically comprises the following steps:

(1) firstly, mixing nickel sulfate, cobalt sulfate and manganese sulfate solution, and then carrying out coprecipitation reaction under alkaline condition to prepare ternary composite precursor (Ni)_xCo_yMn_z）(OH)₂(ii) a Wherein (Ni)_xCo_yMn_z）(OH)₂The molar ratio of Ni, Co and Mn is x: y: z =65:15: 20;

(2) and (2) preparing the ternary composite precursor (Ni) prepared in the step (1)_xCo_yMn_z）(OH)₂Washing with deionized water, pulping, filtering to obtain slurry A with impurity content up to standard, wherein the impurity content up to standard refers to Na in the slurry A⁺The mass fraction is less than or equal to 0.02 percent;

(3) adding a lithium source and potassium metavanadate into the slurry A obtained in the step (2), refining by using a homogenizer, and then performing spray drying to obtain a dried material B, wherein the gap of the homogenizer is set to be 650 mu m, and the homogenizing frequency is 1-3 times;

(4) and (4) calcining the dried material B obtained in the step (3) to obtain the potassium metavanadate dispersion coated nickel-cobalt-manganese ternary cathode material.

2. The method for preparing the nickel-cobalt-manganese ternary cathode material dispersedly coated with potassium metavanadate according to claim 1, wherein the method comprises the following steps: in the step (1), the alkaline solution selected under the alkaline condition is an ammonia-containing sodium hydroxide solution.

3. The method for preparing the nickel-cobalt-manganese ternary cathode material dispersedly coated with potassium metavanadate according to claim 1, wherein the method comprises the following steps: in the step (1), the conditions of the coprecipitation reaction are that the pH is controlled to be 10.5-12, the temperature is 5070 ℃, the stirring speed is 300-800 r/min, and the aging time is 2-5 h.

4. The method for preparing the nickel-cobalt-manganese ternary cathode material dispersedly coated with potassium metavanadate according to claim 1, wherein the method comprises the following steps: in the step (2), the temperature of the deionized water is 40-70 ℃.

5. The method for preparing the nickel-cobalt-manganese ternary cathode material dispersedly coated with potassium metavanadate according to claim 1, wherein the method comprises the following steps: in the step (3), the lithium source is one or a mixture of lithium hydroxide, lithium carbonate and lithium acetate.

6. The method for preparing the nickel-cobalt-manganese ternary cathode material dispersedly coated with potassium metavanadate according to claim 1, wherein the method comprises the following steps: in the step (3), the ternary composite precursor (Ni)_xCo_yMn_z）(OH)₂The molar ratio of the lithium source to the potassium metavanadate is 1:1.06: n, wherein n is more than or equal to 0.001 and less than or equal to 0.01.

7. The method for preparing the nickel-cobalt-manganese ternary cathode material dispersedly coated with potassium metavanadate according to claim 1, wherein the method comprises the following steps: in the step (3), the inlet air temperature of the spray drying is 200-.

8. The method for preparing the nickel-cobalt-manganese ternary cathode material dispersedly coated with potassium metavanadate according to claim 1, wherein the method comprises the following steps: in the step (4), the calcination condition of the drying material B is to heat the drying material B to 600-900 ℃ at a heating rate of 10-30 ℃/min in the air or oxygen atmosphere, and then to preserve heat for 8-16 h.

Technical Field

The invention relates to the technical field of lithium ion batteries, in particular to a preparation method of a potassium metavanadate dispersed and coated nickel-cobalt-manganese ternary cathode material.

Background

As is well known, the lithium ion power battery for vehicles in the early stage of China mainly adopts a lithium iron phosphate battery, the theoretical gram capacity of the lithium iron phosphate material is 170mAh/g, the working voltage is 3.20V, and the energy density of the lithium iron phosphate single battery can reach 140Wh/Kg to the maximum. In order to further meet the long-mileage requirement of the pure electric vehicle, how to increase the energy density of the battery becomes a difficult problem for governments and large companies. According to the related high specific energy lithium ion battery product index planning in ' 2012-2020 ' of the development planning of energy-saving and new energy automobile industry ' of China, the energy density requirement of a single battery reaches 350Wh/kg by 2020. The current commonly used lithium iron phosphate battery can not meet the requirement, and the limiting factor is that the gram capacity of the lithium iron phosphate anode material is low, so that governments and enterprises are required to develop the anode material with high gram capacity and high voltage platforms. Therefore, the nickel cobalt lithium manganate ternary material enters the field of vision of people.

L iNi lithium nickel cobalt manganese oxide_xCo_yMn_zO₂(x + y + z = 1) is a novel lithium ion battery cathode material. The lithium ion battery anode material has the advantages of high theoretical capacity, stable structure, good cycle performance, wide discharge voltage range, low price, environmental friendliness and the like, and is considered to be the most promising lithium ion battery anode material. However, the nickel cobalt lithium manganate still has many problems as the lithium ion battery anode material, firstly, Mn is generated at high potential³⁺The disproportionation reaction occurs to dissolve from the surface of the active material, and secondly, structural distortion easily occurs during repeated lithium deintercalation, causing rapid capacity fading, and particularly at higher temperatures, the phenomenon of capacity fading is more prominent.

Although the conventional modification methods such as doping and coating improve the specific discharge capacity to a certain extent, the conventional modification methods adopt mechanical addition, have the problems of aggregation, difficult uniform mixing and unstable performance improvement, and the mixing is difficult to be uniform due to the slow solid-phase diffusion speed, so that the electrochemical performance stability is not high and the cycle performance is poor.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for preparing a nickel-cobalt-manganese ternary positive electrode material coated with potassium metavanadate in a dispersed manner, wherein the surface of a nickel-cobalt-manganese ternary positive electrode is coated with potassium metavanadate (KVO)₃) The structure stability of the surface of the nickel-cobalt-manganese ternary positive electrode material is improved, and the ion mobility of the nickel-cobalt-manganese ternary positive electrode material is improved, so that the electrochemical performance of the nickel-cobalt-manganese ternary positive electrode material is improved.

The technical scheme of the invention is as follows:

a preparation method of a potassium metavanadate dispersed coated nickel-cobalt-manganese ternary cathode material specifically comprises the following steps:

(1) firstly, mixing nickel sulfate, cobalt sulfate and manganese sulfate solution, and then carrying out coprecipitation reaction under alkaline condition to prepare ternary composite precursor (Ni)_xCo_yMn_z）(OH)₂(ii) a Wherein (Ni)_xCo_yMn_z）(OH)₂The molar ratio of Ni, Co and Mn is x: y: z =65:15: 20;

(2) and (2) preparing the ternary composite precursor (Ni) prepared in the step (1)_xCo_yMn_z）(OH)₂Washing with deionized water, pulping, filtering to obtain slurry A with impurity content up to standard, wherein the impurity content up to standard refers to Na in the slurry A⁺The mass fraction is less than or equal to 0.02 percent;

(3) adding a lithium source and potassium metavanadate into the slurry A obtained in the step (2), refining by using a homogenizer, and then performing spray drying to obtain a dried material B, wherein the gap of the homogenizer is set to be 650 mu m, and the homogenizing frequency is 1-3 times;

(4) and (4) calcining the dried material B obtained in the step (3) to obtain the potassium metavanadate dispersion coated nickel-cobalt-manganese ternary cathode material.

In the step (1), the alkaline solution selected under the alkaline condition is an ammonia-containing sodium hydroxide solution.

In the step (1), the conditions of the coprecipitation reaction are that the pH is controlled to be 10.5-12, the temperature is 5070 ℃, the stirring speed is 300-800 r/min, and the aging time is 2-5 h.

In the step (2), the temperature of the deionized water is 40-70 ℃.

In the step (3), the lithium source is one or a mixture of lithium hydroxide, lithium carbonate and lithium acetate.

In the step (3), the ternary composite precursor (Ni)_xCo_yMn_z）(OH)₂The molar ratio of the lithium source to the potassium metavanadate is 1:1.06: n, wherein n is more than or equal to 0.001 and less than or equal to 0.01.

In the step (3), the inlet air temperature of the spray drying is 200-.

In the step (4), the calcination condition of the drying material B is to heat the drying material B to 600-900 ℃ at a heating rate of 10-30 ℃/min in the air or oxygen atmosphere, and then to preserve heat for 8-16 h.

The invention has the advantages that:

(1) the invention coats KVO on the surface of the ternary anode₃The surface structure stability of the material is improved, and the ion mobility of the material is improved, so that the electrochemical performance of the ternary material is improved; the nickel-cobalt-manganese ternary cathode material prepared by the invention has the advantages of good dispersibility, uniform size, high sphericity and loose secondary particles, is beneficial to the infiltration of electrolyte, and improves the diffusion rate of lithium ions, thereby improving the rate capability and the cycle performance.

(2) Under the action of stator of homogenizer, the slurry A forms the comprehensive effects of strong reciprocating hydraulic shearing, friction, centrifugal extrusion, liquid flow expansion, etc. in the narrow interval of stator and rotor, so that the precursor particles of the product are fully refined and highly dispersed.

(3) The invention adopts a spray drying mode for drying, greatly shortens the production period, prevents the components of the precursor from segregating, and ensures the uniformity and high purity of the product; in addition, the particle size of the precursor powder is controlled by adjusting the diameter of the atomizing nozzle, the sphericity of the material can be improved, the dried material does not need to be crushed and sieved, and the production process is simplified.

Drawings

FIG. 1 is XRD patterns of Coating-1 prepared in example 1 of the present invention, Coating-2 prepared in example 2, Coating-3 prepared in example 3 and pure ternary positive electrode material (NCM) in comparative example.

FIG. 2 is an SEM image of Coating-1 prepared in example 1 of the present invention.

FIG. 3 is an SEM image of Coating-2 prepared in example 2 of the present invention.

FIG. 4 is an SEM image of Coating-3 prepared in example 3 of the present invention.

FIG. 5 is an SEM image of a pure ternary material (NCM) in a comparative example.

FIG. 6 is a graph of 0.2C first discharge, 1C discharge, 2C discharge, 0.2C discharge, and 1C cycle for 50 weeks for Coating-1 prepared in example 1, Coating-2 prepared in example 2, and Coating-3 prepared in example 3 of the present invention and a pure ternary positive electrode material (NCM) in the comparative example.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.