阅读说明：本技术 一种核壳结构的无钴二元正极材料及其制备方法 (Cobalt-free binary anode material with core-shell structure and preparation method thereof ) 是由 马明远 董丰恺 娄忠良 孙伟 张萍 郭平 于 2021-08-03 设计创作，主要内容包括：本发明属于锂离子电池技术领域,具体涉及一种核壳结构的无钴二元正极材料的制备方法,通过共沉淀反应得到具有核壳结构的氢氧化物前驱体,氢氧化物前驱体再与锂源烧结,得到核壳结构的无钴二元正极材料。本发明方法实现前驱体颗粒中的Ni含量从核到壳呈降低趋势,降低了表层Ni含量,从而提高材料表层自身结构稳定性并降低与电解液之间的副反应；通过本发明方法制备得到的正极材料,Ni含量从核到壳呈降低,利于材料表面Ni含量的最小化,体现了高循环和高安全性的优势；本发明工艺简单,反应易控制,商业化前景大,产品成本低,一致性好,电性能优异且更稳定。(The invention belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method of a cobalt-free binary anode material with a core-shell structure. The method of the invention realizes the reduction trend of the Ni content in the precursor particles from the core to the shell, and reduces the Ni content of the surface layer, thereby improving the structural stability of the surface layer of the material and reducing the side reaction with the electrolyte; the Ni content of the anode material prepared by the method is reduced from the core to the shell, so that the minimization of the Ni content on the surface of the material is facilitated, and the advantages of high cycle and high safety are embodied; the method has the advantages of simple process, easy control of reaction, large commercialization prospect, low product cost, good consistency, excellent electrical property and more stability.)

1. A preparation method of a cobalt-free binary anode material with a core-shell structure is characterized by comprising the following steps:

s1, in a reaction kettle filled with nitrogen protection, deionized water is used as a base solution;

s2, continuously flowing a nickel-manganese mixed salt solution with a molar ratio of R, a sodium hydroxide solution and an ammonia water solution into a reaction kettle with a certain volume according to a certain flow ratio;

s3, under the conditions of temperature of 40-70 ℃ and stirring speed of 200-600 r/min, adjusting ammonia concentration, controlling pH to be 10.5-13.0, and carrying out precipitation reaction on a nickel-manganese mixed salt solution, a sodium hydroxide solution and an ammonia water solution to obtain a precursor U;

s4, continuously flowing a nickel-manganese mixed salt solution with a molar ratio of Q, a sodium hydroxide solution and an ammonia water solution into a reaction kettle with a certain volume according to a certain flow ratio by taking the precursor as a base solution;

s5, under the conditions of temperature of 40-70 ℃ and stirring speed of 200-600 r/min, adjusting ammonia concentration, controlling pH to be 10.5-13.0, and carrying out precipitation reaction on a nickel-manganese mixed salt solution, a sodium hydroxide solution and an ammonia water solution to obtain a precursor V;

s6, precipitating, washing and drying the precursor V in an oven to obtain binary nickel-manganese hydroxide with a core-shell structure;

s7, uniformly mixing the binary nickel-manganese hydroxide with a lithium source, and sintering to obtain the cobalt-free binary anode material.

2. The preparation method of the cobalt-free binary anode material with the core-shell structure according to claim 1, wherein the mixed salt solution of nickel and manganese is prepared from nickel salt and manganese salt according to a mol ratio of 1-3: 1-2, R is not less than Q, and the nickel salt is selected from one of nickel sulfate, nickel chloride or nickel nitrate; the manganese salt is selected from one of manganese sulfate, manganese chloride or manganese nitrate.

3. The preparation method of the cobalt-free binary anode material with the core-shell structure according to claim 1, wherein the cobalt-free binary anode material is of a core-shell structure and comprises a core layer and a shell layer, and the content of nickel element in the core layer is higher than that in the shell layer.

4. The preparation method of the cobalt-free binary anode material with the core-shell structure according to claim 1, wherein the molar concentration of metal ions in the nickel-manganese mixed salt solution is 1.2-3.5 mol/L.

5. The preparation method of the cobalt-free binary anode material with the core-shell structure according to claim 1, wherein the concentration of the sodium hydroxide solution is 20-32% wt, and the concentration of the ammonia water solution is 10-25% wt.

6. The preparation method of the cobalt-free binary anode material with the core-shell structure according to claim 1, wherein the precursor V is precipitated, washed by a centrifuge until the pH of the flowing deionized water is 7.0-9.5, and dried by an oven at 85-110 ℃ to obtain the binary nickel-manganese hydroxide.

7. The method for preparing the cobalt-free binary positive electrode material with the core-shell structure according to claim 1, wherein the molar ratio of the binary nickel manganese hydroxide to the lithium source is 1.0-1.2: 1, and the lithium source is selected from one of lithium nitrate, lithium carbonate or lithium hydroxide.

8. The preparation method of the cobalt-free binary anode material with the core-shell structure according to claim 1, wherein the sintering temperature is 790-980 ℃ and the sintering time is 12-24 h.

9. The preparation method of the cobalt-free binary positive electrode material with the core-shell structure, according to claim 1, is characterized in that the median particle size of the cobalt-free binary positive electrode material is 3.0-13.0 μm.

10. A cobalt-free binary positive electrode material obtained by the preparation method of any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a cobalt-free binary anode material with a core-shell structure and a preparation method thereof.

Background

The positive electrode material in the lithium ion battery mainly has two functions: firstly, the electrochemical performance is safety and cycle life; and secondly, cost constitution, namely a cost economic index. The positive electrode material is one of the major components of the cost of the battery at present, compared to other battery materials, and therefore, research on the positive electrode material has become a current research focus, particularly on the ternary positive electrode material. However, the cobalt element in the ternary material has relatively high price and large price fluctuation, and cannot meet the actual requirement of low cost of enterprises, and the price is difficult to bring substantial price to customers, so the expensive cobalt element is abandoned in the invention, and the nickel-manganese binary anode material with relatively low cost is prepared. The existing research (a lithium manganate anode material of a lithium ion battery and a preparation method thereof CN108878852A, a gradient core-shell anode material of the lithium ion battery and a synthesis method CN103236537A) proves that the core-shell structure is a means capable of effectively improving the cycle performance and the thermal stability of the anode material. The core-shell structure generally uses high Ni content as a core and high Mn and Co content as a shell, and aims to reduce the Ni content of the material surface layer, thereby improving the structural stability of the material surface layer and reducing side reactions with electrolyte.

Disclosure of Invention

The invention aims to provide a preparation method of a cobalt-free binary anode material under the condition of not sacrificing the structural stability, so that the production cost is reduced, the cycle performance, the safety and the rate capability of the anode material are improved, the process flow is simplified, and the reaction is easy to control.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a preparation method of a cobalt-free binary anode material with a core-shell structure comprises the following steps:

s1, in a reaction kettle filled with nitrogen protection, deionized water is used as a base solution;

s2, continuously flowing a nickel-manganese mixed salt solution with a molar ratio of R, a sodium hydroxide solution and an ammonia water solution into a reaction kettle with a certain volume according to a certain flow ratio;

s3, under the conditions of temperature of 40-70 ℃ and stirring speed of 200-600 r/min, adjusting ammonia concentration, controlling pH to be 10.5-13.0, and carrying out precipitation reaction on a nickel-manganese mixed salt solution, a sodium hydroxide solution and an ammonia water solution to obtain a precursor U;

s4, continuously flowing a nickel-manganese mixed salt solution with a molar ratio of Q, a sodium hydroxide solution and an ammonia water solution into a reaction kettle with a certain volume according to a certain flow ratio by taking the precursor as a base solution;

s5, under the conditions of temperature of 40-70 ℃ and stirring speed of 200-600 r/min, adjusting ammonia concentration, controlling pH to be 10.5-13.0, and carrying out precipitation reaction on a nickel-manganese mixed salt solution, a sodium hydroxide solution and an ammonia water solution to obtain a precursor V;

s6, precipitating, washing and drying the precursor V in an oven to obtain binary nickel-manganese hydroxide;

s7, uniformly mixing the binary nickel-manganese hydroxide with a lithium source, and sintering to obtain the cobalt-free binary anode material.

Preferably, the nickel-manganese mixed salt solution is prepared from nickel salt and manganese salt according to the mol ratio of 1-3: 1-2, R is not less than Q, and the nickel salt is selected from one of nickel sulfate, nickel chloride or nickel nitrate; the manganese salt is selected from one of manganese sulfate, manganese chloride or manganese nitrate.

Preferably, the cobalt-free binary anode material is of a core-shell structure and comprises a core layer and a shell layer, wherein the content of nickel elements in the core layer is higher than that in the shell layer.

Preferably, the molar concentration of the metal ions in the nickel-manganese mixed salt solution is 1.2-3.5 mol/L.

Preferably, the concentration of the sodium hydroxide solution is 20-32% wt, and the concentration of the ammonia water solution is 10-25% wt.

Preferably, after the precursor V is precipitated, the precursor V is washed by a centrifuge until the pH value of the flowing deionized water is 7.0-9.5, and then the precursor V is dried by an oven at 85-110 ℃ to obtain the binary nickel-manganese hydroxide.

Preferably, the molar ratio of the binary nickel manganese hydroxide to a lithium source is 1.01-1.2: 1, and the lithium source is selected from one of lithium nitrate, lithium carbonate or lithium hydroxide.

Preferably, the sintering temperature is 790-980 ℃, and the sintering time is 12-24 h.

Preferably, the median particle size of the cobalt-free binary positive electrode material is 3.0-13.0 μm.

Based on one general inventive concept, another object of the present invention is to protect the cobalt-free binary positive electrode material obtained by any one of the above-mentioned preparation methods.

Compared with the prior art, the method provided by the invention has the advantages that the Ni content in the precursor particles is reduced from the core to the shell, and the Ni content in the surface layer is reduced, so that the structural stability of the surface layer of the material is improved, and the side reaction with electrolyte is reduced; the Ni content of the anode material prepared by the method is reduced from the core to the shell, so that the minimization of the Ni content on the surface of the material is facilitated, and the advantages of high cycle and high safety are embodied; the invention has simple process, easy control of reaction, suitability for commercialization, large market prospect, low cost of the prepared product, good consistency, excellent electrical property and more stability.

Drawings

Fig. 1 is a cycle curve of the core-shell structure cathode material prepared in example 1 of the present invention.

Detailed Description

The present invention will be further described with reference to specific embodiments for making the objects, technical solutions and advantages of the present invention more apparent, but the present invention is not limited to these examples. It should be noted that, without conflict, any combination between the embodiments or technical features described below may form a new embodiment. In the invention, all parts and percentages are mass units, and the adopted equipment, raw materials and the like can be purchased from the market or are commonly used in the field. The methods in the following examples are conventional in the art unless otherwise specified.

The following detailed description of specific embodiments of the invention refers to the accompanying drawings.

Example 1

1. Deionized water is used as a base solution in the whole reaction kettle filled with nitrogen protection;

2. a mixed salt solution of nickel sulfate and manganese chloride with a molar ratio of 3:1 is recorded as a solution A; a mixed salt solution of nickel sulfate and manganese chloride with a molar ratio of 1:1 is recorded as a solution B;

3. controlling the solution A to be 1.6mol/L, the sodium hydroxide solution to be 29 wt% and the ammonia water solution to be 13 wt%, continuously flowing into a reaction kettle according to a conventional flow ratio, adjusting the ammonia concentration and controlling the pH value to be 12.5 under the conditions that the temperature is 45 ℃ and the stirring speed is 350r/min, and carrying out precipitation reaction on the mixed salt solution of nickel sulfate and manganese chloride, the sodium hydroxide solution and the ammonia water solution to obtain Ni_0.75Mn_0.25(OH)₂A precursor, marked as precursor U;

4. controlling the precursor C as a base solution, controlling the solution B to be 1.8mol/L, controlling the sodium hydroxide solution to be 15 wt% and the ammonia water solution to be 12 wt%, continuously flowing into a reaction kettle according to a conventional flow ratio, adjusting the ammonia concentration and controlling the pH to be 12.0 at the temperature of 45 ℃ and the stirring speed of 350r/min, and carrying out precipitation reaction on the mixed salt solution of nickel sulfate and manganese chloride, the sodium hydroxide solution and the ammonia water solution to obtain the Ni-based catalyst_0.75Mn_0.25(OH)₂Is a nucleus, Ni_0.5Mn_0.5(OH)₂Being shells [ (Ni)_0.75Mn_0.25)_1-x·(Ni_0.5Mn_0.5)_x](OH)₂The precursor V is marked as a precursor V, and after the precursor V is precipitated, the precursor V is washed by a centrifuge until the pH value of the flowing deionized water is 8.2, and then the precursor V is dried by an oven at 105 ℃ to obtain the binary nickel-manganese hydroxide with the core-shell structure;

5. the obtained binary nickel manganese hydroxide and lithium nitrate are uniformly mixed according to the mol ratio of 1.09: 1, and then are sintered at the high temperature of 810 ℃ for 15 hours to obtain the cobalt-free binary anode material with the median particle size of 5.2 mu m and the core-shell structure, and as can be seen from figure 1, the prepared cobalt-free binary anode material has excellent and stable cycle performance.

Comparative example 1

1. Deionized water is used as a base solution in the whole reaction kettle filled with nitrogen protection;

2. controlling the concentration of a mixed salt solution of nickel sulfate and manganese chloride with a molar ratio of 3:1 to be 1.6mol/L, controlling the concentration of a sodium hydroxide solution to be 29 percent and controlling an ammonia water solution to be 13 percent, continuously flowing the mixed salt solution into a reaction kettle according to a conventional flow ratio, adjusting the ammonia concentration and controlling the pH value to be 12.5 under the conditions of 45 ℃ and a stirring speed of 350r/min, and carrying out precipitation reaction on the mixed salt solution of nickel sulfate and manganese chloride, the sodium hydroxide solution and the ammonia water solution to obtain Ni_0.75Mn_0.25(OH)₂A precursor;

3、Ni_0.75Mn_0.25(OH)₂and uniformly mixing the precursor and lithium nitrate according to the molar ratio of 1.02: 1, and then sintering at the high temperature of 810 ℃ for 15 hours to obtain the cobalt-free binary anode material with the core-shell structure and the median particle size of 5.0 mu m.

Example 2

1. Deionized water is used as a base solution in the whole reaction kettle filled with nitrogen protection;

2. a mixed salt solution of nickel sulfate and manganese chloride with a molar ratio of 3:1 is recorded as a solution A; a mixed salt solution of nickel sulfate and manganese chloride with a molar ratio of 1:1 is recorded as a solution B;

3. controlling the solution A to be 3.5mol/L, the sodium hydroxide solution to be 20 wt% and the ammonia water solution to be 25 wt%, continuously flowing into a reaction kettle according to a conventional flow ratio, adjusting the ammonia concentration and controlling the pH value to be 11.0 under the conditions that the temperature is 60 ℃ and the stirring speed is 400r/min, and carrying out precipitation reaction on the mixed salt solution of nickel sulfate and manganese chloride, the sodium hydroxide solution and the ammonia water solution to obtain Ni_0.75Mn_0.25(OH)₂A precursor, marked as precursor U;

4. using precursor C as base solution, dissolvingControlling the solution B to be 3.2mol/L, the sodium hydroxide solution to be 20 wt% and the ammonia water solution to be 20 wt%, continuously flowing into a reaction kettle according to the conventional flow proportion, regulating the ammonia concentration and controlling the pH to be 11.0 at the temperature of 65 ℃ and the stirring speed of 400r/min, and carrying out precipitation reaction on the mixed salt solution of nickel sulfate and manganese chloride, the sodium hydroxide solution and the ammonia water solution to obtain the Ni-based catalyst_0.75Mn_0.25(OH)₂Is a nucleus, Ni_0.5Mn_0.5(OH)₂Being shells [ (Ni)_0.75Mn_0.25)_1-x·(Ni_0.5Mn_0.5)_x](OH)₂The precursor V is marked as a precursor V, and after the precursor V is precipitated, the precursor V is washed by a centrifuge until the pH value of the flowing deionized water is 7.8, and then the precursor V is dried by an oven at 100 ℃ to obtain the binary nickel-manganese hydroxide with the core-shell structure;

5. uniformly mixing the obtained binary nickel manganese hydroxide and lithium nitrate according to the mol ratio of 1.2: 1, and then sintering at the high temperature of 900 ℃ for 20 hours to obtain the cobalt-free binary anode material with the median particle size of 10.5 mu m and the core-shell structure.

Example 3

1. Deionized water is used as a base solution in the whole reaction kettle filled with nitrogen protection;

2. a mixed salt solution of nickel sulfate and manganese chloride with a molar ratio of 3:1 is recorded as a solution A; a mixed salt solution of nickel sulfate and manganese chloride with a molar ratio of 1:2 is recorded as a solution B;

3. controlling the solution A to be 2.5mol/L, the sodium hydroxide solution to be 25 wt% and the ammonia water solution to be 18 wt%, continuously flowing into a reaction kettle according to a conventional flow ratio, adjusting the ammonia concentration and controlling the pH to be 11.5 under the conditions that the temperature is 55 ℃ and the stirring speed is 450r/min, and carrying out precipitation reaction on the mixed salt solution of nickel sulfate and manganese chloride, the sodium hydroxide solution and the ammonia water solution to obtain Ni_0.75Mn_0.25(OH)₂A precursor, marked as precursor U;

4. taking precursor C as base solution, controlling solution B at 2.5mol/L, sodium hydroxide solution at 25 wt% and ammonia water solution at 20 wt%, continuously flowing into reaction kettle at 60 deg.C under stirringStirring at 450r/min, adjusting ammonia concentration, and controlling pH to 11.5 to make mixed salt solution of nickel sulfate and manganese chloride, sodium hydroxide solution and ammonia water solution produce precipitation reaction to obtain Ni_0.75Mn_0.25(OH)₂Is a nucleus, Ni_0.5Mn_0.5(OH)₂Being shells [ (Ni)_0.75Mn_0.25)_1-x·(Ni_0.5Mn_0.5)_x](OH)₂The precursor V is marked as a precursor V, and after the precursor V is precipitated, the precursor V is washed by a centrifuge until the pH value of the flowing deionized water is 8.5, and then the precursor V is dried by an oven at 95 ℃ to obtain the binary nickel-manganese hydroxide with the core-shell structure;

5. uniformly mixing the obtained binary nickel-manganese hydroxide and lithium nitrate according to the mol ratio of 1.02: 1, and then sintering at 890 ℃ for 20 hours to obtain the cobalt-free binary anode material with the median particle size of 7.8 mu m and the core-shell structure.

The above embodiments are merely preferred embodiments of the present invention, and any simple modifications, modifications and alternative changes to the above embodiments according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.