WO2019113870A1

WO2019113870A1 - Lithium-rich manganese-based material and preparation and application thereof

Info

Publication number: WO2019113870A1
Application number: PCT/CN2017/116076
Authority: WO
Inventors: 王二东; 徐衫; 孙公权
Original assignee: 中国科学院大连化学物理研究所
Priority date: 2017-12-11
Filing date: 2017-12-14
Publication date: 2019-06-20
Also published as: CN109904402A

Abstract

A lithium-rich manganese-based material. The lithium-rich manganese-based material is a multiphase heterostructure consisting of a layer structure and a spinel structure, and the molecular formula of the multiphase heterostructure is xLi2MnO3•(1-x)LiMO2•yLiNi0.5Mn1.5O4, wherein 0.3<x<1, 0<y<0.1, and M is more than one or two of iron, chromium, nickel, cobalt, magnesium, aluminum, zinc, and copper. Microscopically, said material is microspheres consisting of layer-structured nanoparticles, spinel-structured nanoparticles, and nanoparticles in which a layer structure and spinel are mutually embedded. The size range of the nanoparticles is 20-500 microns, and the diameter range of the microspheres is 5-20 microns. According to a preparation process of the lithium-rich manganese-based material, a complex spinel-phase lithium-rich manganese-based material having high specific discharge capacity and good cycle stability can be obtained without modification operations such as doping and coating. The preparation process of the present invention is simple, easy to control, good in product consistency, and suitable for mass production.

Description

Lithium-rich manganese-based material and preparation and application thereof

Technical field

The invention belongs to the technical field of lithium ion battery materials, and particularly relates to a lithium-rich manganese-based material xLi2MnO3·(1-x)LiMO2 with a composite spinel phase, and preparation and application thereof.

Background technique

The rapid development of new energy electric vehicles requires lithium ion power batteries with higher energy density. The positive electrode material in lithium ion batteries is the limiting factor for the increase in energy density of lithium ion batteries. Therefore, in order to improve the energy density of a lithium ion power battery, it is urgent to develop a new positive electrode material having a higher specific capacity.

The most common commercial cathode materials available are LiCoO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , Li-Ni-Co-O and Li-Ni-Mn-Co-O materials, and the actual discharge specific capacity of these materials is not exceeded. 200mAh / g, it is difficult to meet the needs of large-capacity batteries. The lithium-rich manganese-based xLi ₂ MnO ₃ ·(1-x)LiMO ₂ material which has appeared in recent years has been developed at home and abroad due to its high capacity (actual first-round discharge specific capacity over 250 mAh/g) and high voltage. hot spot. However, conventional methods such as coprecipitation, sol-gel-derived lithium-rich manganese-based materials have poor coulombic efficiency in the first cycle due to phase transition of the crystal structure from lamellar to spinel, poor cycle stability, and low capacity retention. Achieve the practical application of business. Recently, Jin and Wu et al. used a method of doping fluoride ions and coating polyvinylpyrrolidone-manganese on a prepared lithium-rich manganese-based material to obtain a lithium-rich manganese-based material containing a spinel phase through a maintenance layer. The structure of the spinel phase does not collapse to maintain the cyclic stability of the material. However, these modification methods are complicated and cumbersome, and some require high-tech means such as atomic deposition, and cannot achieve large-scale industrialization. Therefore, there is an urgent need to develop a lithium-rich manganese-based material with a simple preparation method, high specific discharge capacity, and good cycle stability, and a preparation method thereof to meet the demand for large-scale commercial applications.

Summary of the invention

A lithium-rich manganese-based material, which is microscopically a composite structure having a layered structure and a spinel structure, and has a molecular formula of xLi2MnO3·(1-x)LiMO2·yLiNi0.5Mn1.5O4 Where 0.3<x<1, 0<y<0.1. The layered structure and the spinel structure are in the form of a heterogeneous heterostructure. Multiphase refers to two phases of a layered structure and a spinel structure. When the two phases have similar crystal structures, similar atomic layer spacing and thermal expansion coefficient, a heterogeneous heterostructure is formed during the growth of the material. During charge and discharge, this structure facilitates ion migration and diffusion between different phases. Especially in the lithium-rich manganese-based material, the two phases complement each other to make the phase transition of the conventional lithium-rich manganese-based first ring charge. The mechanism changes, avoiding the escape of oxygen, and solves the bottleneck problem that restricts the wide application of lithium-rich manganese-based materials.

A preparation method of the lithium-rich manganese-based material, comprising the following steps,

1) Dissolving one or more of soluble iron salt, soluble chromium salt, soluble nickel salt, soluble cobalt salt, soluble magnesium salt, soluble aluminum salt, soluble zinc salt and soluble copper salt in water, and adding soluble manganese salt Forming solution A;

2) adding a settling agent to the solution A obtained in the step 1), stirring until the solution B is dissolved;

3) The solution B in step 2) is placed in a reaction vessel, causing a hydrothermal reaction at 150 ~ 200 ° C, after the reaction is completed, filtered, washed, dried to obtain a precursor C;

4) after the first step of the calcination in the precursor C in the step 3), the first calcination temperature is 300-700 ° C, the calcination time is 2-10 h;

5) adding a lithium compound to the first calcined product for the second calcination to obtain the lithium-rich manganese-based material, the second calcination temperature is 500-900 ° C, and the calcination time is 3-15 h; the first calcination The temperature is lower than the second calcination temperature.

Another method for preparing the lithium-rich manganese-based material comprises the following steps:

4) performing the first calcination of the precursor C in the step 3), the first calcination temperature is 300-400 ° C, the calcination time is 2-5 h; the second calcination temperature is greater than 400-600 ° C, the calcination time 2-10h; calcination of the mixture after adding the lithium compound, the first calcination temperature is 500-800 ° C, the calcination time is 3-10 h; the second calcination temperature is greater than 800-900 ° C, and the calcination time is 8- 15h.

The invention obtains microspheres composed of nanoparticles with a core-shell structure with a diameter of 5-20 μm by calcining the precursor, and separates the core from the shell by grinding, and the difference in the proportion distribution of the nickel-manganese elements in the core and the shell leads to the nuclear portion and the lithium. The salt reacts to form a spinel phase, and the shell portion reacts with the lithium salt to form a layered lithium-rich manganese-based phase. The product thus is a lithium-rich manganese-based material in a composite spinel phase.

Step 1) The soluble iron salt is one or more of iron nitrate, iron acetate, iron sulfate, and ferric chloride; the soluble chromium salt is one of chromium nitrate, chromium acetate, chromium sulfate, and chromium chloride. Or two or more; the soluble nickel salt is one or more of nickel nitrate, nickel acetate, nickel sulfate, nickel chloride; the soluble cobalt salt is one of cobalt nitrate, cobalt acetate, cobalt sulfate, and cobalt chloride. Or two or more; the soluble magnesium salt is one or more of magnesium nitrate, magnesium acetate, magnesium sulfate, magnesium chloride; the soluble aluminum salt is one of aluminum trichloride, aluminum sulfate, aluminum nitrate, and aluminum chloride. Or two or more; the soluble zinc salt is one or more of zinc nitrate, zinc acetate, zinc sulfate, and zinc chloride; the soluble copper salt is one of copper nitrate, copper acetate, copper sulfate, and copper chloride. Or two or more; the soluble manganese salt is one or more of manganese nitrate, manganese acetate, manganese sulfate, and manganese chloride.

Step 2) The ammonium-containing weakly basic substance is one or more of hexamethylenetetramine, hexamethylenediamine, ammonium hydrogencarbonate, and urea.

These weakly alkaline substances can undergo a reversible hydrolysis reaction in aqueous solution, which causes the reaction to continue in a weakly alkaline environment of 7 < PH ≤ 10 without generating a concentration gradient, thereby ensuring the morphology and structure during the formation of the precursor. And the consistency of the element distribution. The hydrolysis reaction is as follows: hexamethylenetetramine hydrolysis reaction

Hexamethylenediamine hydrolysis reaction

Ammonium bicarbonate double hydrolysis reaction (ammonia water is more ionized than bicarbonate, and hydrolysis is weakly alkaline)

Urea hydrolysis reaction

NH ₂ CONH ₂ +H ₂ O→2NH ₃ +CO ₂

Step 1) the total concentration of metal ions in the solution A is 0.2 ~ 1mol / L;

The concentration of the settling agent added in the step 2) is 0.02 to 0.2 mol·L ^-1 .

The molar ratio of the metal ion to the precipitating agent (ammonium ion in the step 2) is from 0.1 to 0.5.

The lithium compound in the step 4) is one or more selected from the group consisting of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium chloride; the amount of the substance added to the lithium compound is such that the amount of the lithium and manganese elements The ratio is 3:2-4:1.

Step 3) The hydrothermal reaction time is 6-24 hours; the washing is washing with deionized water 2 times or more. The objective is to wash precursor C to neutral without introducing impurities.

The layered structure on the [001] crystal plane includes a layered lithium cobalt oxide structure composed of a laminated lithium layer, an oxygen layer, and a transition metal layer as lamellar repeating units, and a laminated lithium layer, an oxygen layer, and a lithium manganese layer. a layered lithium manganate structure composed of layered repeating units;

The invention adopts hexamethylenetetramine or the like as a precipitating agent, and provides a solution rich in ammonium ions compared with other precipitating agents such as sodium hydroxide, and the hydrolysis of the ammonium ions makes a gradient without pH concentration Reaction environment. When a lithium-rich manganese-based material is synthesized by hydrothermal method, a spinel structure material is obtained at 150 ° C, and a layered structure material is obtained at 200 ° C. Therefore, the hydrothermal temperature of the present invention is 160 to 190 ° C to obtain a layer of a composite spinel phase. Lithium-rich manganese-based material. The present invention is different from the method in which Zhang et al. coats a spinel phase material on an existing layered lithium-rich manganese-based material, and is also different from a method of physically mixing two substances. The present invention aims to disperse the nano-particles by grinding the precursor manganese composite oxide during calcination, resulting in uneven distribution of elements. After the lithium salt is added by using this feature, a part of the product forms a layered lithium-rich manganese-based material, and a part of the product forms a spinel phase manganese-based material, which is compatible with the phase of the nanometer phase. Moreover, the traditional lithium-rich manganese-based material is desorbed from the layered lithium manganate Li2MnO3 during the first charging, which causes oxygen to escape, which is also the main reason for restricting the wide application of lithium-rich manganese-based materials. When the material of the present invention is charged in the first cycle, due to the heterogeneous heterogeneity, the lithium layered lithium manganate Li2MnO3 is delithiated, and the structure is oriented to the layered structure LiNi0 due to the action of the surrounding spinel phase. The conversion of 5Mn0.5O2 avoids the escape of oxygen and solves the fundamental problem of restricting the entry of lithium-rich manganese-based materials into the market. The preparation process does not require doping, coating and the like to obtain a lithium-rich manganese-based material having a high specific discharge capacity and a good cycle stability of the composite spinel phase. The preparation process of the invention is simple, easy to control, good in product consistency, and suitable for large-scale production.

DRAWINGS

1 is a lithium-rich manganese-based cathode material of a composite spinel phase prepared in Example 1 of the present invention, an uncomplexed lithium-rich manganese base prepared in Comparative Example 1, and a coated spinel-rich lithium-manganese group prepared in Comparative Example 2; X-ray diffraction comparison chart;

2 is a graph showing charge and discharge curves of a lithium-rich manganese-based cathode material of a composite spinel phase prepared in Example 1 of the present invention;

3 is a comparison chart of charge-discharge ratio capacity of lithium-rich manganese-based positive electrode materials prepared in Examples 1, 2, and 3 and Comparative Examples 2, 3, and 4 of the present invention;

4 is a graph showing charge and discharge curves of a lithium-free manganese-based cathode material without a composite phase prepared by a sol-gel method of Comparative Example 1;

5 is a graph showing charge and discharge curves of a lithium-rich manganese-based cathode material coated with a spinel phase prepared by a hydrothermal synthesis method of Comparative Example 2;

Fig. 6 is a graph showing the cycle performance of charge and discharge of a lithium-rich manganese-based positive electrode material of a composite spinel phase prepared in Example 1 of the present invention and a positive electrode material prepared in Comparative Example 1, 2 at a magnification of 0.1C.

Detailed ways

The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings.

Example 1

A sample of 0.4Li2MnO3·0.35LiNi0.5Mn0.5O2·0.05LiN0.5Mn1.5O4 was prepared. Weigh the stoichiometric ratio of nickel sulfate and manganese sulfate in deionized water to form solution A with a manganese ion concentration of 0.77 mol/L; add hexamethylenetetramine to obtain a mixed solution B, nickel sulfate and hexamethylene four The molar ratio of amine was 0.15; solution B was transferred to an autoclave and heated at 160 ° C for 12 h. After the reaction is completed, the precipitate is washed and washed several times with deionized water, and dried to obtain precursor C. The precursor C is ground in an agate mortar for several minutes, and then placed in a corundum boat at a heating rate of 5 ° C / min in air. Heating to 350 ° C, constant temperature calcination for 3h, heating to 600 ° C, constant temperature calcination for 5h, then cooled to room temperature at a cooling rate of 5 ° C / min, adding 1.25 times of lithium hydroxide, grinding with an agate mortar to obtain precursor B; The precursor B was placed in a corundum boat, heated to 700 ° C in air at a heating rate of 5 ° C / min, calcined at a constant temperature for 5 h, heated to 850 ° C, calcined at a constant temperature for 10 h, and ground with an agate mortar to obtain a composite spinel. The lithium phase lithium-rich cathode material 0.4Li2MnO3·0.35LiNi0.5Mn0.5O2·0.05LiMn2O4. The resulting microspherical lithium-rich manganese-based material has a diameter of 10 μm and is composed of particles having a size of 20 to 50 nm. X-ray diffraction (XRD) is shown in Fig. 1. The charge-discharge curve is shown in Fig. 2. The charge-discharge performance chart is shown in Fig. 3. The cycle performance of the positive electrode material at charge and discharge at 0.1C is shown in Fig. 6.

Example 2

A sample of 0.4Li2MnO3·0.35LiNi0.5Mn0.5O2·0.05Li0.5Mn1.5O4 was prepared. Weigh the stoichiometric ratio of nickel sulfate and manganese sulfate in deionized water to form solution A with a manganese ion concentration of 0.77 mol/L; add urea to obtain a mixed solution B, and the molar ratio of nickel sulfate to urea is 0.15; In Example 1, a lithium-rich manganese-based positive electrode material of the composite spinel phase was finally obtained, 0.4Li2MnO3·0.35LiNi0.5Mn0.5O2·0.05LiMn2O4. The resulting microspherical lithium-rich manganese-based material has a diameter of 20 microns and is composed of particles having a size of 30-50 nm. Its charge and discharge curve is shown in Figure 3.

Example 3

A sample of 0.4Li2MnO3·0.35LiNi0.5Mn0.5O2·0.05Li0.5Mn1.5O4 was prepared. The stoichiometric ratio of nickel sulfate and manganese sulfate was dissolved in deionized water to form a solution A having a manganese ion concentration of 0.77 mol/L; and a mixed solution B was obtained by adding ammonium hydrogencarbonate, and the molar ratio of nickel sulfate to ammonium hydrogencarbonate was 0.15. The subsequent steps were the same as those in Example 1, and finally a lithium-rich manganese-based positive electrode material of the composite spinel phase, 0.4Li2MnO3·0.35LiNi0.5Mn0.5O2·0.05LiMn2O4, was obtained. The resulting microspherical lithium-rich manganese-based material has a diameter of 30 microns and is composed of particles having a size of 50-100 nm. Its charge and discharge performance diagram is shown in Figure 3.

Comparative example 1

0.4Li2MnO3·0.4LiNi0.5Mn0.5O2 was prepared by sol-gel method. Lithium hydroxide, nickel sulfate, cobalt sulfate and manganese sulfate were dissolved in deionized water at a stoichiometric ratio, and stirred at 60 ° C for 30 min at a constant temperature to form a solution A having a manganese ion concentration of 0.134 mol/L; the solution was at 5 ° C / The heating rate of min is raised to 120 ° C, citric acid is added to dissolve, the amount of citric acid is added as the sum of the moles of the added metal ions, and the mixture is stirred under reflux for 90 min, and then the solvent is evaporated to obtain the precursor A; the precursor is placed in the corundum boat. It is heated to 450 ° C in air at a heating rate of 5 ° C / min, calcined at a constant temperature for 3 h, then heated to 850 ° C at a heating rate of 5 ° C / min, calcined at a constant temperature for 12 h, and then cooled to room temperature to obtain a rich spinel-free phase. Lithium manganese-based material 0.4Li2MnO3·0.4LiNi0.5Mn0.5O2. X-ray diffraction (XRD) is shown in Fig. 1, and its charge and discharge curve is shown in Fig. 4. The cycle performance of charge and discharge at a magnification of 0.1 C is shown in Fig. 6.

Comparative example 2

0.4Li2MnO3·0.35LiNi0.5Mn0.5O2·0.05LiNi0.5Mn1.5O4 was prepared by hydrothermal synthesis. Precursor C was obtained according to the method of Example 1; precursor C was mixed with 1.25 times of lithium hydroxide, ground for a few minutes in an agate mortar, placed in a corundum boat, sintered in two stages in the air, without grinding in the middle. The treatment was carried out at 450 ° C for 5 h and at 850 ° C for 12 h to obtain a layered lithium-rich manganese-based positive electrode material 0.4Li2MnO3·0.35LiNi0.5Mn0.5O2. Then, 0.05 g of PVP was dissolved in 10 ml of deionized water, and 1 g of the above product was ultrasonically dispersed and stirred for 2 hours. Add 5% manganese sulfate, stir to a thick slurry, and dry at 90 ° C under vacuum. The lithium-rich manganese-based material 0.4Li2MnO3·0.35LiNi0.5Mn0.5O2·0.05LiMn2O4 coated with the spinel phase was fired in air at 750 ° C for 5 h. X-ray diffraction (XRD) is shown in Fig. 1, and its charge and discharge curve is shown in Fig. 5. The cycle performance of charge and discharge at a magnification of 0.1 C is shown in Fig. 6.

Comparative example 3

0.4Li2MnO3·0.35LiNi0.5Mn0.5O2·0.05LiNi0.5Mn1.5O4 was prepared by hydrothermal synthesis. The precursor C was obtained according to the method of Example 2; the subsequent step was the same as in Comparative Example 2, and the charge and discharge performance chart is shown in FIG.

Comparative example 4

0.4Li2MnO3·0.35LiNi0.5Mn0.5O2·0.05LiNi0.5Mn1.5O4 was prepared by hydrothermal synthesis. The precursor C was obtained according to the method of Example 3; the subsequent step was the same as in Comparative Example 2, and the charge and discharge performance diagram is shown in FIG.

Claims

A lithium-rich manganese-based material characterized in that the lithium-rich manganese-based material is a heterogeneous heterostructure composed of a layered structure and a spinel structure, and has a molecular formula of xLi 2 MnO 3 ·(1) -x) LiMO 2 · yLiNi 0.5 Mn 1.5 O 4 , where 0.3 < x < 1, 0 < y <0.1; M is one or two of iron, chromium, nickel, cobalt, magnesium, aluminum, zinc, copper the above;

Microscopically, the microsphere consists of layered nano-particles, spinel-structured nanoparticles and nano-particles with layered structure and spinel intertwined. The size of the nanoparticles ranges from 20 to 500 nm. The diameter ranges from 5 to 20 microns.
A method for preparing a lithium-rich manganese-based material according to claim 1, comprising the steps of:

1) Dissolving one or more of soluble iron salt, soluble chromium salt, soluble nickel salt, soluble cobalt salt, soluble magnesium salt, soluble aluminum salt, soluble zinc salt and soluble copper salt in water, and adding soluble manganese salt Forming solution A;

2) adding a settling agent to the solution A obtained in the step 1), stirring until the solution B is dissolved;

3) The solution B in step 2) is placed in a reaction vessel, causing a hydrothermal reaction at 150 ~ 200 ° C, after the reaction is completed, filtered, washed, dried to obtain a precursor C;

4) The precursor C in the step 3), the first constant temperature calcination after the pulverization, the first calcination temperature is 300-700 ° C, the calcination time is 2-10 h;

Adding a lithium compound to the first calcined product for the second calcination to obtain the lithium-rich manganese-based material; the second calcination temperature is 500-900 ° C, the calcination time is 3-15 h; the first calcination temperature is low At the second calcination temperature.
A method of preparing a lithium-rich manganese-based material according to claim 2, wherein:

The step 4) is that the first calcination process after the precursor C is composed of two steps, the first calcination temperature of the precursor C after the pulverization is 300-400 ° C, and the calcination time is 2-5 h; The two-step calcination temperature is greater than 400-600 ° C, and the calcination time is 2-10 h;

The second calcination process of the mixture after adding the lithium compound is composed of two steps, the first calcination temperature is 500-800 ° C, the calcination time is 3-10 h; the second step calcination temperature is greater than 800-900 ° C, calcination time It is 8-15h.
A method of preparing a lithium-rich manganese-based material according to claim 2, wherein:

Step 1) The soluble iron salt is one or more of iron nitrate, iron acetate, iron sulfate, and ferric chloride; the soluble chromium salt is one of chromium nitrate, chromium acetate, chromium sulfate, and chromium chloride. Or two or more; the soluble nickel salt is one or more of nickel nitrate, nickel acetate, nickel sulfate, nickel chloride; the soluble cobalt salt is one of cobalt nitrate, cobalt acetate, cobalt sulfate, and cobalt chloride. Or two or more; the soluble magnesium salt is one or more of magnesium nitrate, magnesium acetate, magnesium sulfate, magnesium chloride; the soluble aluminum salt is one of aluminum trichloride, aluminum sulfate, aluminum nitrate, and aluminum chloride. Or two or more; the soluble zinc salt is one or more of zinc nitrate, zinc acetate, zinc sulfate, and zinc chloride; the soluble copper salt is one of copper nitrate, copper acetate, copper sulfate, and copper chloride. Or two or more; the soluble manganese salt is one or more of manganese nitrate, manganese acetate, manganese sulfate, and manganese chloride.
The method for preparing a lithium-rich manganese-based material according to claim 2, wherein the precipitating agent is a weakly basic substance containing ammonium; and the weakly basic substance containing ammonium is hexamethylene four. One or more of an amine, hexamethylenediamine, ammonium hydrogencarbonate, and urea.
The method for preparing a lithium-rich manganese-based material according to claim 2, wherein the total concentration of metal ions in the solution A in step 1) is 0.2 to 1 mol/L; and the final concentration of the settling agent added in the step 2) It is 0.02 to 0.2 mol/L.
The method for preparing a lithium-rich manganese-based material according to claim 2 or 6, wherein the molar ratio of the metal ion to the ammonium ion in the precipitating agent in the step 2) is from 0.1 to 0.5.
The method for preparing a lithium-rich manganese-based material according to claim 2, wherein the lithium compound in the step 4) is one or more of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium chloride; The lithium compound is added in an amount such that the amount ratio of the lithium to manganese element is from 3:2 to 4:1.
The method for preparing a lithium-rich manganese-based material according to claim 2, wherein the step of the hydrothermal reaction in step 3) is 8 to 24 hours; and the washing process is to wash the water twice or more.
Use of a lithium-rich manganese-based material according to claim 1 as a positive electrode active material in a lithium ion battery.