阅读说明：本技术 一种锂离子电池正极材料助熔剂大面积多点快速成核晶体生长方法 (Method for growing large-area multi-point rapid nucleation crystals of lithium ion battery anode material fluxing agent ) 是由 王坤鹏 张建秀 周利 范立群 任衍彪 李凤丽 刘泳 于 2020-12-11 设计创作，主要内容包括：本发明公开了一种锂离子电池正极材料助熔剂大面积多点快速成核晶体生长方法。按照锂离子电池正极材料的化学式将化学计量比的锂源、过渡金属源和螯合剂,按照比例溶解于去离子水中,形成一次溶液；加入助溶剂,提高过渡金属源的溶解度,充分搅拌至溶质完全溶解,并形成透明的二次溶液；再加入少量锂源,形成富锂环境；然后再加入固态多孔模板剂,增大成核面积以及成核点的数量；滴入乙酸或氨水,调节pH值；然后置于微波水热反应器中进行充分反应；最后将反应产物进行固液分离、清洗、干燥,获得锂离子电池正极材料。该方法获得的锂离子电池正极材料颗粒度均匀,结晶度高,各晶面发育良好,成核和结晶速度快。本方法大大增加成核面积和成核点的数量,并且可以防止晶粒之间的吸附和团聚。(The invention discloses a method for growing a large-area multi-point fast nucleation crystal of a lithium ion battery anode material fluxing agent. Dissolving a lithium source, a transition metal source and a chelating agent in stoichiometric ratio in deionized water according to the chemical formula of the lithium ion battery cathode material to form a primary solution; adding a cosolvent to improve the solubility of the transition metal source, and fully stirring until the solute is completely dissolved to form a transparent secondary solution; then adding a small amount of lithium source to form a lithium-rich environment; then adding a solid porous template agent to increase the nucleation area and the number of nucleation points; dripping acetic acid or ammonia water to adjust the pH value; then placing the mixture in a microwave hydrothermal reactor for full reaction; and finally, carrying out solid-liquid separation, cleaning and drying on the reaction product to obtain the lithium ion battery anode material. The lithium ion battery anode material obtained by the method has uniform granularity, high crystallinity, good crystal face development and high nucleation and crystallization speed. The method greatly increases the nucleation area and the number of nucleation points, and can prevent adsorption and agglomeration among grains.)

1. A method for growing a large-area multi-point rapid nucleation crystal of a lithium ion battery anode material fluxing agent is characterized by comprising the following steps:

1) dissolving a lithium source, a transition metal source and a chelating agent in stoichiometric ratio in deionized water according to the chemical formula of the lithium ion battery cathode material to form a primary solution;

2) adding a cosolvent into the solution obtained in the step 1 to improve the solubility of the transition metal source, and fully stirring until the solute is completely dissolved to form a transparent secondary solution;

3) adding a small amount of lithium source into the transparent solution obtained in the step 2 to form a lithium-rich environment;

4) adding a solid porous template into the lithium-rich transparent solution obtained in the step 3 to increase the nucleation area and the number of nucleation points;

5) dripping acetic acid or ammonia water into the solution obtained in the step 4, and adjusting the pH value;

6) putting the solution obtained in the step 5 into a microwave hydrothermal reactor for full reaction;

7) and (4) carrying out solid-liquid separation, cleaning and drying on the reactant obtained in the step (6) to obtain the lithium ion battery anode material with uniform size.

2. The method for growing large-area multi-point rapid nucleation crystals of a flux for a positive electrode material of a lithium battery as claimed in claim 1, wherein: the lithium ion anode material in the step 1) comprises lithium-based phosphate with a chemical formula of LiMPO₄(M = Fe, Co, Ni, Mn), and a ternary cathode material NCM of the formula LiNi _x Co _y Mn _z O₂ (x + y + z = 1), the lithium source and the transition metal source being water-soluble acetates, and the chelating agent being ammonium hydroxide.

3. The method for growing large-area multi-point rapid nucleation crystals of a flux for a positive electrode material of a lithium battery as claimed in claim 1, wherein: the cosolvent in the step 2) is lithium sulfate nLi₂SO₄And lithium iodate LiIO₃The content of the cosolvent is adjusted to ensure that the concentration of the plated metal ions is 0.07-0.11 mol/L.

4. The method for growing large-area multi-point rapid nucleation crystals of a flux for a positive electrode material of a lithium battery as claimed in claim 1, wherein: in the step 3), the lithium-rich environment is as follows: stoichiometric lithium concentration: actual lithium concentration = 1: 1.03-2.80.

5. The method for growing large-area multi-point rapid nucleation crystals of a flux for a positive electrode material of a lithium battery as claimed in claim 1, wherein: in the step 4), the solid porous template is porous silicon carbide, a carbon porous material or porous alumina.

6. The method for growing large-area multi-point rapid nucleation crystals of a flux for a positive electrode material of a lithium battery as claimed in claim 1, wherein: in the step 5), the pH value of the melt is adjusted to 7-9.

7. The method for growing large-area multi-point rapid nucleation crystals of a flux for a positive electrode material of a lithium battery as claimed in claim 1, wherein: in the step 6), the microwave hydrothermal reaction time is 5-30 minutes, and the temperature is 150-^oC。

8. The method for growing large-area multi-point rapid nucleation crystals of a flux for a positive electrode material of a lithium battery as claimed in claim 1, wherein: in the step 7), reaction products are separated and washed at 70-120 DEG^oAnd C, drying for 10-48 hours.

Technical Field

The invention relates to a method for growing a large-area multi-point fast nucleation crystal of a lithium ion battery anode material fluxing agent, belonging to the technical field of crossing of a crystal material and a lithium ion battery.

Background

In recent years, the rapid development of new energy automobiles puts higher and higher requirements on the energy density of power lithium ion batteries. For mainstream lithium iron phosphate and ternary NCM power lithium batteries, the method for improving the nickel content and the charging voltage is two commonly adopted capacity improvement means. However, as the nickel content and the charging voltage increase, grain boundaries of the positive electrode material particles are cracked and even broken, thereby drastically deteriorating the cycle performance and safety performance. This technical bottleneck severely hinders the development of high capacity cell products.

In recent years, single crystals without grain boundaries are used to replace traditional polycrystalline powder particles to break through the technical bottleneck, and the method has become the hot point of key breakthrough in the lithium battery industry in the world recently. The preparation level of the single crystal anode material is increasingly becoming a technical standard for weighing various material manufacturers.

Compared with the traditional secondary powder particles, the traditional positive electrode material is secondary spherical polycrystalline powder particles of about 10 microns formed by agglomeration of primary particles of 200-300nm, a large number of grain boundaries exist inside the particles, and the grain boundaries are easy to crack due to anisotropic lattice change in the charging and discharging processes of the battery, so that the secondary particles are crushed, the specific surface area and the interface side reaction are rapidly increased, the impedance of the battery is further increased, and the performance is rapidly reduced. The single crystal type anode material is not provided with crystal boundaries inside, so that the lithium ion transmission efficiency can be improved, the side reaction between the anode and the electrolyte can be reduced, the problems of crystal boundary breakage and performance deterioration can be effectively solved, the voltage of the whole system can be increased to a new height, the energy density of the battery is improved, the stability of the anode material is enhanced, and a brand new feasible solution is provided for the safety and long service life of the high-energy density lithium ion battery. As described above, although single crystals have many advantages over conventional spherical secondary particles, the technology for preparing single crystal type cathode materials is still in a stage that has not been fully developed.

Disclosure of Invention

The invention aims to provide a method for growing a large-area multi-point fast nucleation crystal of a lithium ion battery anode material fluxing agent, so as to solve the problems in the background technology.

The invention adopts the following technical scheme that the method for growing the large-area multi-point fast nucleation crystal of the lithium ion battery anode material fluxing agent comprises the following steps:

1) dissolving a lithium source, a transition metal source and a chelating agent in stoichiometric ratio in deionized water according to the chemical formula of the lithium ion battery cathode material to form a primary solution;

2) adding a cosolvent into the solution obtained in the step 1 to improve the solubility of the transition metal source, and fully stirring until the solute is completely dissolved to form a transparent secondary solution;

3) adding a small amount of lithium source into the transparent solution obtained in the step 2 to form a lithium-rich environment;

4) adding a solid porous template into the lithium-rich transparent solution obtained in the step 3 to increase the nucleation area and the number of nucleation points;

5) dripping acetic acid or ammonia water into the solution obtained in the step 4, and adjusting the pH value;

6) putting the solution obtained in the step 5 into a microwave hydrothermal reactor for full reaction;

7) and (4) carrying out solid-liquid separation, cleaning and drying on the reactant obtained in the step (6) to obtain the lithium ion battery anode material with uniform size.

As a further scheme of the invention: the lithium ion anode material in the step 1) comprises lithium-based phosphate with a chemical formula of LiMPO₄(M = Fe, Co, Ni, Mn), and a ternary cathode material NCM of the formula LiNi _x Co _y Mn _z O₂ (x + y + z = 1), the lithium source and the transition metal source being water-soluble acetates, and the chelating agent being ammonium hydroxide.

As a further scheme of the invention: the cosolvent in the step 2) is lithium sulfate nLi₂SO₄And lithium iodate LiIO₃The content of the cosolvent is adjusted to ensure that the concentration of the plated metal ions is 0.07-0.11 mol/L.

As a further scheme of the invention: in the step 3), the lithium-rich environment is as follows: stoichiometric lithium concentration: actual lithium concentration = 1: 1.03-2.80.

As a further scheme of the invention: in the step 4), the solid porous template is porous silicon carbide, a carbon porous material or porous alumina.

As a further scheme of the invention: in the step 5), the pH value of the melt is adjusted to 7-9.

As a further scheme of the invention: in the step 6), the microwave hydrothermal reaction time is 5-30 minutes, and the temperature is 150-^oC。

As a further scheme of the invention: in the step 7), reaction products are separated and washed at 70-120 DEG^oAnd C, drying for 10-48 hours.

Compared with the prior art, the method has the beneficial effects that the size of the lithium ion battery anode material obtained by the method is 300-800nm, the granularity is uniform, the crystallinity is high, each crystal face grows well, and the nucleation and crystallization speed is high. In addition, the method is efficient and energy-saving: using a conventional laboratory preparation as an example, 10ml of deionized water was heated to 220 kJ with a total energy efficiency of 28 kJ for microwave radiation^oC is about 8.4 kJ, and the total energy consumption is about 7.6 kJ, so that the energy can be saved by about 70 percent compared with other solid-phase synthesis methods and conventional hydrothermal methods. Finally, the bookThe method adopts a solid porous template agent, so that the nucleation area and the number of nucleation points are greatly increased, and the adsorption and agglomeration among crystal grains can be prevented.

Drawings

FIG. 1 is a photograph of a crystal prepared by the method of the present invention;

FIG. 2 is a phase diagram of the optimum process for crystal growth according to the present invention.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely explained below with reference to the drawings in the embodiments of the present invention.

Example 1

Single crystal anode material LiMnPO₄And (4) preparing.

Lithium acetate LiCH as initial raw material in stoichiometric ratio₃CO₂∙2H₂O, manganous acetate Mn (CH)₃CO₂)₂Monoammonium hydrogen phosphate (NH)₄)₂HPO₄And ammonium hydroxide NH₄OH is dissolved in deionized water, and is magnetically stirred for 30 minutes at the stirring temperature of 80 DEG^oC; gradually adding cosolvent lithium sulfate Li2SO4, and adjusting the content of the cosolvent to make the concentration of metal manganese ions be 0.07 mol/L; add excess LiCH incrementally₃CO₂∙2H₂And O, controlling the lithium-rich environment as follows: stoichiometric lithium concentration: actual lithium concentration = 1: 1.03; adding a small amount of porous silicon carbide into the solution; adding a certain amount of acetic acid or ammonia water to adjust the pH value of the melt to 7; then placing the test tube in a microwave hydrothermal furnace for reaction for 5 minutes at the reaction temperature of 150 DEG C^oC, the rotating speed is 300 rpm; placing the reaction product in a centrifuge for separation, wherein the rotation speed of the centrifuge is 1200 rpm; washing the reaction precipitate with deionized water and anhydrous ethanol three times, placing in a drying oven at 70 deg.C^oC is dried for 10 hours to obtain LiMnPO with the grain diameter of about 500nm, good crystallinity and good and complete crystal face development₄And (3) a positive electrode single crystal. The crystal photograph is shown in FIG. 1. In addition, an optimal process phase diagram for the crystal growth was determined, as shown in fig. 2. The phase diagram is divided into the following five regions:

and (3) region I: when the metal ion concentration is less than 0.05 and the pH is less than 6.5, no crystalline phase is generated;

and (II) zone: a crystalline region of a positive electrode material;

and (3) zone III: when 6.5<pH<At 9.5, an impurity phase (Mn) is formed₃(OH)₂；

Zone IV: when the pH is >9.5 and the concentration is >0.06, an impurity phase LiOH is formed;

preferred V regions: when the C is more than 0.08 and less than 0.11 and the pH value is between 7 and 9, the single crystal particles of the anode material with good and complete crystal morphology and moderate particle size can be obtained.

Example 2

Single crystal anode material LiCoPO₄And (4) preparing.

Lithium acetate LiCH as initial raw material in stoichiometric ratio₃CO₂∙2H₂O, cobalt (Co) acetate (CH)₃CO₂)₂Monoammonium hydrogen phosphate (NH)₄)₂HPO₄And ammonium hydroxide NH₄OH is dissolved in deionized water, and the mixture is magnetically stirred for 20 minutes at the stirring temperature of 70 DEG^oC; gradually adding a cosolvent lithium iodate LiIO3, and adjusting the content of the cosolvent to ensure that the concentration of metal manganese ions is 0.09 mol/L; add excess LiCH incrementally₃CO₂∙2H₂And O, controlling the lithium-rich environment as follows: stoichiometric lithium concentration: actual lithium concentration = 1: 1.2; adding a small amount of carbon porous material into the solution; adding a certain amount of acetic acid or ammonia water to adjust the pH value of the melt to 8; then placing the test tube in a microwave hydrothermal furnace for reaction for 10 minutes at the reaction temperature of 180 DEG C^oC, the rotating speed is 200 rpm; placing the reaction product in a centrifuge for separation, wherein the rotation speed of the centrifuge is 1500 rpm; washing the reaction precipitate with deionized water and anhydrous ethanol three times, placing in a drying oven at 80 deg.C^oC is dried for 24 hours to obtain LiCoPO with the particle size of about 300nm, good crystallinity and good and complete crystal face₄And (3) a positive electrode single crystal.

Example 3

LiFePO as single crystal anode material₄And (4) preparing.

Lithium acetate LiCH as initial raw material in stoichiometric ratio₃CO₂∙2H₂O, ferrous acetate Co (CH)₃CO₂)₂Monoammonium hydrogen phosphate (NH)₄)₂HPO₄And ammonium hydroxide NH₄OH is dissolved in deionized water, and is magnetically stirred for 30 minutes at the stirring temperature of 90 DEG^oC; gradually adding a cosolvent lithium iodate LiIO3, and adjusting the content of the cosolvent to ensure that the concentration of metal manganese ions is 0.1 mol/L; add excess LiCH incrementally₃CO₂∙2H₂And O, controlling the lithium-rich environment as follows: stoichiometric lithium concentration: actual lithium concentration = 1: 1.3; adding a small amount of porous alumina into the solution; adding a certain amount of acetic acid or ammonia water to adjust the pH value of the melt to 9; then placing the test tube in a microwave hydrothermal furnace for reaction for 15 minutes at the reaction temperature of 190 DEG C^oC, the rotating speed is 230 rpm; placing the reaction product in a centrifuge for separation, wherein the rotation speed of the centrifuge is 1300 rpm; washing the reaction precipitate with deionized water and anhydrous ethanol three times, placing in a drying oven at 90 deg.C^oC is dried for 20 hours to obtain LiFePO with the grain diameter of about 800nm, good crystallinity and good and complete crystal face₄And (3) a positive electrode single crystal.

Example 4

Single crystal anode material LiFe_0.5Ni_0.5PO₄And (4) preparing.

Lithium acetate LiCH as initial raw material in stoichiometric ratio₃CO₂∙2H₂O, ferrous acetate Fe (CH)₃CO₂)₂Nickel (II) acetate Ni (CH)₃CO₂)₂Monoammonium hydrogen phosphate (NH)₄)₂HPO₄And ammonium hydroxide NH₄OH is dissolved in deionized water, and is magnetically stirred for 40 minutes at the stirring temperature of 100^oC; gradually adding a cosolvent lithium iodate LiIO3, and adjusting the content of the cosolvent to ensure that the concentration of metal manganese ions is 0.2 mol/L; add excess LiCH incrementally₃CO₂∙2H₂And O, controlling the lithium-rich environment as follows: stoichiometric lithium concentration: actual lithium concentration = 1: 1.5; adding a small amount of porous alumina into the solution; adding a certain amount of acetic acid or ammonia water to adjust the pH value of the melt to 8; then placing the test tube in a microwave hydrothermal furnace for reaction for 20 minutesReaction temperature 200^oC, the rotating speed is 250 rpm; placing the reaction product in a centrifuge for separation, wherein the rotation speed of the centrifuge is 1600 rpm; washing the reaction precipitate with deionized water and anhydrous ethanol three times, placing in a drying oven at 100 deg.C^oC drying for 48 hours to obtain the LiFe with the grain diameter of about 500nm, good crystallinity and good and complete crystal face development_0.5Ni_0.5PO₄And (3) a positive electrode single crystal.

The foregoing is a preferred embodiment of the present invention, and it will be apparent to those skilled in the art that variations, modifications, substitutions and alterations can be made in the embodiment without departing from the principles and spirit of the invention.