CN103943845A - Preparation method of layered-spinel composite solid solution positive-electrode material - Google Patents

Abstract

The invention relates to a layered-spinel composite solid solution cathode material doped with sodium ions, belonging to the field of new energy materials. Firstly, dissolve the nickel salt and manganese salt weighed according to the stoichiometric ratio with deionized water to form a multi-element metal salt solution; secondly, prepare an alkali solution; Under the action of an external field, react while stirring and adding, control the reaction temperature, and control the adding speed of the salt and alkali solution; continue to stir after the reaction is completed, continue to stir and then stand still, filter to obtain solids, and wash with deionized water to the pH value Below 7.8, dry to obtain the precursor of nickel-manganese multi-component lithium-ion battery positive electrode material; then mix with lithium salt and sodium source weighed according to the stoichiometric ratio, undergo mechanical activation, roasting, and finally cool to obtain a layered-spinel composite Solid solution cathode material. Through the above method, the rate performance of the positive electrode material can be effectively improved.

Description

A kind of preparation method of layered-spinel composite solid solution cathode material

technical field

The invention relates to a layered-spinel composite solid solution cathode material doped with sodium ions, belonging to the field of new energy materials.

Background technique

In recent years, the lithium-rich solid solution cathode material Li _1.5 Ni _0.25 Mn _0.75 O _2.5 has become a research hotspot due to its high discharge specific capacity, good cycle performance, and high energy density, and is considered to be a new generation of electric vehicles. The preferred cathode material for lithium-ion power batteries.

With the deepening of research, people found that although Li _1.5 Ni _0.25 Mn _0.75 O _2.5 cathode materials have high discharge specific capacity and energy density, they also have shortcomings such as low first Coulombic efficiency and poor rate performance. These shortcomings are serious It affects the application of Li _1.5 Ni _0.25 Mn _0.75 O _2.5 cathode materials in the field of electric vehicles.

In the research on the modification of Li _1.5 Ni _0.25 Mn _0.75 O _2.5 cathode materials, it was found that the spinel-type LiNi _0.5 Mn _1.5 O ₄ cathode materials belonged to the cubic crystal system and had special three-dimensional lithium ion diffusion channels, which ensured its good Rate performance, because LiNi _0.5 Mn _1.5 O ₄ and Li _1.5 Ni _0.25 Mn _0.75 O _2.5 have the same oxygen stacking mode, and can be prepared using the same precursor (nickel-manganese molar ratio of 1:3) and synthesis method, M. M. Thackeray took the lead in proposing the method of modifying layered solid solution _{Li 1.5 Ni 0.25} Mn _0.75 O _2.5 by using spinel-type LiNi _0.5 Mn 1.5 O ₄ , and prepared a new type of layered-spinel composite solid solution cathode material Li _{0.5 +x} Ni _0.25 Mn _0.75 O _2+x/2 (0<x<1), the material has both layered and spinel structures, combining LiNi _0.5 Mn _1.5 O ₄ and Li _1.5 Ni _0.25 Mn _0.75 O _2.5 Charge-discharge characteristics, and has a high discharge capacity, the first Coulombic efficiency and good cycle performance, so it is expected to become a new generation of lithium-ion power battery cathode material.

However, the study found that the rate performance of the new layered-spinel composite solid solution cathode material is not very good, so it is necessary to further improve its rate performance.

Contents of the invention

The present invention provides a new method for improving the rate performance of the layered-spinel composite solid solution positive electrode material Li _0.5+x Ni _0.25 Mn _0.75 O _2+x/2 (0<x<1). The specific content of the invention is as follows:

1. First, dissolve the nickel salt and manganese salt weighed according to the stoichiometric ratio with deionized water, and configure a multi-element metal salt solution with a total metal ion molar concentration of 0.3-3mol/L. Secondly, prepare an alkali solution; then, The salt solution and the alkali solution with an excess of 20% according to the stoichiometric ratio are reacted under the action of an ultrasonic external field while stirring, the temperature is controlled at 40°C-80°C, the adding speed of the salt and alkali solution is well controlled, and the pH value of the reaction system is controlled. In 9-12; after the reaction is completed, continue to stir, continue to stir and then stand still, filter to obtain a solid, wash with deionized water until the pH value is below 7.8, and dry to obtain the precursor of the nickel-manganese multi-element lithium-ion battery positive electrode material, molecular formula It is: Ni _0.25 Mn _0.75 (OH) ₂ .

The alkaline solution is an aqueous solution of sodium hydroxide, potassium hydroxide or lithium hydroxide with a concentration of 1-4mol/L.

The stirring speed while stirring is 100-600 rev/min.

The time for the continuation of stirring is 0.5-12 h.

The standing time is 1-5 h.

2. Then mix with lithium salt and sodium source weighed according to the stoichiometric ratio, after mechanical activation for 1-12h, roast at 400-600°C for 1-12h, then roast at 750-900°C for 8-24h, and finally cool The layered-spinel composite solid solution cathode material Li _0.5+x Na _y Ni _0.25 Mn _0.75 O _2+(x+y)/2 (0<x+y<1;0<y<0.3) was obtained.

In the step 1, the nickel salt is nickel sulfate, nickel chloride, nickel nitrate or nickel acetate; the manganese salt is manganese sulfate, manganese chloride, manganese nitrate or manganese acetate. the

In the step 2, the lithium salt is lithium hydroxide, lithium carbonate, lithium nitrate or lithium acetate, and the sodium source is sodium carbonate, sodium hydroxide, sodium sulfate, and sodium nitrate.

Through the above method, the prepared sodium ion-doped Li _0.5+x Na _y Ni _0.25 Mn _0.75 O _2+(x+y)/2 (0<x+y<1;0<y<0.3) cathode material is effective greatly improved the rate performance of the cathode material.

Description of drawings

Figure 1 SEM image of the Li _1.1 Na _0.1 Ni _0.25 Mn _0.75 O _2.35 positive electrode material doped with sodium ions in Example 1. It can be seen from the figure that the Li _1.1 Na _0.1 Ni _0.25 Mn _0.75 O _2.35 positive electrode doped with sodium ions The material has a better spherical shape, which is conducive to improving the energy density of the positive electrode material.

Figure 2 Comparison of the rate performance of the Li _1.1 Na _0.1 Ni _0.25 Mn _0.75 O _2.35 positive electrode material doped with sodium ions in Example 1 and the slightly doped Li _1.2 Ni _0.25 Mn _0.75 O _2.35 positive electrode material. It can be seen from the figure that after The rate performance of Na ion-doped cathode materials has been significantly improved.

Detailed ways

Embodiment 1: at first, nickel sulfate, manganese sulfate are dissolved with deionized water, and the total metal ion molar concentration that is configured into 1L is the polynary metal salt solution of 0.3mol/L, secondly, the sodium hydroxide solution of preparation concentration 1mol/L ; Then, react the salt solution and 20% excess sodium hydroxide solution according to the stoichiometric ratio under the action of an ultrasonic external field, control the temperature at 40°C, and the stirring speed is 100 rpm, and control the addition of salt and alkali solutions Speed, so that the pH value of the reaction system is controlled at 9; after the reaction is completed, continue to stir for 0.5 h, let stand for 1 h, filter to obtain a solid, wash with deionized water until the pH value is below 7.8, and dry to obtain nickel cobalt manganese hydrogen Oxide precursor, the molecular formula is: Ni _0.25 Mn _0.75 (OH) ₂ ; then add lithium carbonate and sodium carbonate according to the stoichiometric ratio to mix, after mechanical activation for 1h, roast at 600°C for 1h, and then roast at 900°C for 8h, Finally, after cooling, a sodium-doped layered-spinel composite solid solution cathode material Li _1.1 Na _0.1 Ni _0.25 Mn _0.75 O _2.35 is obtained.

Embodiment 2: first, nickel sulfate and manganese sulfate are dissolved with deionized water, and the total metal ion molar concentration of 1L is configured as a polynary metal salt solution of 1mol/L, and secondly, a potassium hydroxide solution with a concentration of 3mol/L is prepared; Next, react the salt solution and 20% excess potassium hydroxide solution according to the stoichiometric ratio under the action of an ultrasonic external field, control the temperature at 50°C, and the stirring speed at 600 rpm, and control the addition speed of the salt and alkali solutions , so that the pH value of the reaction system is controlled at 12; after the reaction is completed, continue to stir for 12 h, let stand for 5 h, filter to obtain a solid, wash with deionized water until the pH value is below 7.8, and dry to obtain nickel cobalt manganese hydroxide precursor, the molecular formula is: Ni _0.25 Mn _0.75 (OH) ₂ ; then lithium carbonate and sodium carbonate were added according to the stoichiometric ratio, after mechanical activation for 12 hours, calcined at 400°C for 12h, and then calcined at 750°C for 24h, finally Cooling to obtain a sodium-doped layered-spinel composite solid solution cathode material Li _1.1 Na _0.2 Ni _0.25 Mn _0.75 O _2.4 .

Embodiment 3: at first, nickel sulfate, manganese sulfate are dissolved with deionized water, and the total metal ion molar concentration that is configured into 1L is the polynary metal salt solution of 0.5mol/L, and secondly, the sodium hydroxide of preparation concentration 1.5mol/L solution; then, react the salt solution and the sodium hydroxide alkali solution with an excess of 20% according to the stoichiometric ratio under the action of an ultrasonic external field, control the temperature at 60 ° C, and stir at a speed of 300 rpm to control the salt and alkali solution The addition speed of the reaction system is controlled at a pH value of 11; after the reaction is completed, continue to stir for 4 h, let stand for 2 h, filter to obtain a solid, wash with deionized water until the pH value is below 7.8, and dry to obtain nickel-cobalt Manganese hydroxide precursor, the molecular formula is: Ni _0.25 Mn _0.75 (OH) ₂ ; then add lithium carbonate and sodium carbonate according to the stoichiometric ratio to mix, after mechanical activation for 5 hours, bake at 400°C for 5 hours, and then bake at 880°C 12h, and finally cooled to obtain the sodium-doped layered-spinel composite solid solution cathode material Li _1.2 Na _0.1 Ni _0.25 Mn _0.75 O _2.4 .

Embodiment 4: at first, nickel sulfate, manganese sulfate are dissolved with deionized water, and the total metal ion molar concentration that is configured into 1L is the polynary metal salt solution of 0.5mol/L, and secondly, the lithium hydroxide solution of preparation concentration 2mol/L Then, the salt solution and the lithium hydroxide alkali solution with an excess of 20% according to the stoichiometric ratio are reacted under the effect of an ultrasonic external field, the temperature is controlled at 70° C., and the stirring speed is 300 revolutions/min. Adding speed, so that the pH value of the reaction system is controlled at 11; after the reaction is completed, continue to stir for 3 h, let stand for 2 h, filter to obtain a solid, wash with deionized water until the pH value is below 7.8, and dry to obtain nickel cobalt manganese Hydroxide precursor, the molecular formula is: Ni _0.25 Mn _0.75 (OH) ₂ ; then add lithium carbonate and sodium carbonate according to the stoichiometric ratio, after mechanical activation for 4 hours, bake at 500°C for 6 hours, and then bake at 850°C for 16 hours , and finally cooled to obtain the sodium-doped layered-spinel composite solid solution cathode material Li _1.2 Na _0.2 Ni _0.25 Mn _0.75 O _2.45 .

Embodiment 5: First, nickel sulfate and manganese sulfate are dissolved with deionized water, and it is configured into 1 L of a multi-element metal salt solution with a total metal ion molar concentration of 1 mol/L, and secondly, a sodium hydroxide solution with a concentration of 2 mol/L is prepared; Next, react the salt solution and the 20% excess sodium hydroxide alkali solution according to the stoichiometric ratio under the action of an ultrasonic external field, control the temperature at 80°C, and the stirring speed at 400 rpm, and control the addition of the salt and alkali solutions Speed, so that the pH value of the reaction system is controlled at 10; after the reaction is completed, continue to stir for 3 h, let stand for 3 h, filter to obtain a solid, wash with deionized water until the pH value is below 7.8, and dry to obtain nickel cobalt manganese hydrogen Oxide precursor, the molecular formula is: Ni _0.25 Mn _0.75 (OH) ₂ ; then add lithium carbonate and sodium carbonate according to the stoichiometric ratio, after mechanical activation for 2 hours, bake at 500°C for 4 hours, and then bake at 850°C for 15 hours, Finally, after cooling, a sodium-doped layered-spinel composite solid solution cathode material Li _0.9 Na _0.2 Ni _0.25 Mn _0.75 O _2.3 is obtained.

Claims (8)

1. a preparation method for stratiform-spinelle composite solid solution positive electrode, is characterized in that comprising the steps:

(1) first, the nickel salt weighing, manganese salt are dissolved and be configured to multi-element metal salting liquid with deionized water by stoichiometric proportion, secondly, preparation aqueous slkali; Then, multi-element metal salting liquid and the excessive aqueous slkali of stoichiometric proportion are stirred and add limit to react below in the effect of ultrasonic external field, control temperature at 40 DEG C-80 DEG C, control the speed that adds of salt, aqueous slkali well, make pH value of reaction system be controlled at 9-12; Continue after completion of the reaction to stir, after continuing to stir, leave standstill, filter, obtain solid content, wash to pH value below 7.8 with deionized water, be dried, obtain the polynary precursor of lithium ionic cell positive material of nickel manganese, molecular formula is: Ni _0.25mn _0.75(OH) ₂;

(2) then and the lithium salts taking by stoichiometric proportion and sodium source mix, through mechanical activation 1-12h, roasting 1-12h at 400-600 DEG C, then at 750-900 DEG C roasting 8-24h, last cooling stratiform-spinelle composite solid solution positive electrode Li that obtains _0.5+xna _yni _0.25mn _0.75o _{2+ (x+y)/2}, 0<x+y<1; 0<y<0.3.

2. the preparation method of a kind of stratiform-spinelle composite solid solution positive electrode as claimed in claim 1, is characterized in that: total metal ion molar concentration of described multi-element metal salting liquid is 0.3-3mol/L.

3. the preparation method of a kind of stratiform-spinelle composite solid solution positive electrode as claimed in claim 1, is characterized in that: the excessive finger stoichiometric proportion excessive 20% of described stoichiometric proportion.

4. the preparation method of a kind of stratiform-spinelle composite solid solution positive electrode as claimed in claim 1, is characterized in that: described aqueous slkali is the aqueous solution of NaOH, potassium hydroxide or lithium hydroxide, and concentration is 1-4mol/L.

5. the preparation method of a kind of stratiform-spinelle composite solid solution positive electrode as claimed in claim 1, is characterized in that: the mixing speed that stir on described limit is turn/min of 100-600.

6. the preparation method of a kind of stratiform-spinelle composite solid solution positive electrode as claimed in claim 1, is characterized in that: the time that described continuation is stirred is 0.5-12 h; Described time of repose is 1-5 h.

7. the preparation method of a kind of stratiform-spinelle composite solid solution positive electrode as claimed in claim 1, is characterized in that: in described step 1, nickel salt is nickelous sulfate, nickel chloride, nickel nitrate or nickel acetate; Manganese salt is manganese sulfate, manganese chloride, manganese nitrate or manganese acetate.

8. the preparation method of a kind of stratiform-spinelle composite solid solution positive electrode as claimed in claim 1, is characterized in that: in described step 2, lithium salts is lithium hydroxide, lithium carbonate, lithium nitrate or lithium acetate, sodium source is sodium carbonate, NaOH, sodium sulphate, sodium nitrate.