CN103956456A - Halogen anion doped lithium-rich positive electrode material as well as preparation method and application of positive electrode material - Google Patents

Abstract

The invention relates to a halogen anion-doped lithium-rich cathode material for a secondary battery, a preparation method and application thereof. The expression is: Li[Li _(1-2x)/3 M _x Mn _(2-x)/3 ]O _2-z A _z , M is Co, Ni, Al, Mg, Zn, Ga, B, Zr, At least one or a combination of Ti, Ca, Ce, Y, Nb elements, A = at least one or a combination of Cl, Br or I, 0<x<0.5;0<z≤0.5; when M= When one or a combination of Ni, Co and A=Cl, x≠0.2. The preparation step is to introduce the halogen anion A according to the stoichiometric ratio during the preparation of the layered lithium-rich oxide positive electrode material Li[Li _(1-2x)/3 M _x Mn _(2-x)/3 ]O ₂ , and prepare Into a solution, solidified, dried and roasted. When the invention is used as the positive electrode material of the lithium ion battery, the first charge and discharge efficiency of the material can be improved; the structural transformation of the material in the electrochemical cycle is suppressed. The invention improves the electrochemical performance of the lithium-rich layered oxide cathode material, and has the characteristics of high initial charge and discharge efficiency, high capacity, good cycle performance, simple preparation process and good reproducibility.

Description

Lithium-rich cathode material doped with halogen anion and its preparation method and application

technical field

The invention relates to a halogen anion-doped lithium-rich cathode material for a secondary battery, a preparation method and application thereof.

Background technique

Due to the development of science and technology, people's requirements for energy storage are getting higher and higher. Lithium-ion batteries have become a research hotspot because of their advantages such as high energy density, relatively green environmental protection and long service life. As a key part of lithium-ion batteries, cathode materials play an important role. The layered lithium-rich oxide cathode material Li[Li _(1-2x)/3 M _x Mn _(2-x)/3 ]O ₂ has become the most promising material for next-generation lithium-ion batteries because of its high specific capacity exceeding 200mAh/g. possible cathode material. However, there are still some deficiencies in the current layered lithium-rich oxide cathode materials, mainly including: the first irreversible capacity loss caused by the low initial charge and discharge efficiency, the layered structure is easy to transform into a spinel structure during the cycle, and the voltage The platform is lowered, which in turn causes problems such as a decrease in energy density.

In order to improve these problems, according to the existing literature reports, the methods for modifying layered lithium-rich oxide cathode materials mainly include surface coating, other pretreatment methods and bulk ion doping. Chinese patents CN200980150179.6 and CN201110434564.2 report that coating lithium-rich cathode materials with metal fluoride can improve their electrochemical performance. CN201110111035.9 uses oxidants such as persulfate or sulfate to pretreat the surface of the material, so that the first-time efficiency and high-rate discharge capacity of the material are improved. In terms of bulk phase doping, current reports mainly focus on metal cation doping, for example: CN200910186311.0 reports a method for improving the cycle performance and rate performance of materials by cation doping; CN201210391471.0 and CN201210391672.0 respectively A method for the preparation of Li-rich solid solution cathode materials using doped trivalent ions and Fe-Cu-Sn ions is reported. In terms of anion doping, CN201310087241 reported a method of modifying materials by doping polyanions such as PO ₄ ^3- , SO ₄ ^2- , A1O ₂ ^- ; CN200980138690.4 used fluorine doping to improve the performance of materials. CN201210216042.X adopts the method of doping chloride ions, but the material described in it can only contain Li, Ni, Co, Mn, O and Cl elements in the expression, and the content of Li is fixed as Li1.2.

Contents of the invention

The purpose of the present invention is to provide a halogen anion-doped layered lithium-rich oxide positive electrode material and its preparation method to improve the existing shortcomings of lithium-rich materials. The present invention has the advantages of simple preparation method, high specific capacity of electrode materials, high rate and Good cycle performance and other advantages.

The expression of a halogen anion-doped layered lithium-rich oxide cathode material provided by the present invention is: Li[Li _(1-2x)/3 M _x Mn _(2-x)/3 ]O _2-z A _z , M is at least one or a combination of Co, Ni, Al, Mg, Zn, Ga, B, Zr, Ti, Ca, Ce, Y, Nb elements, A = one of Cl, Br or I or Its combination, 0<x<0.5;0<z≤0.5; when M=Ni, Co or a combination thereof and A=Cl, x≠0.2.

The preparation step is to introduce the halogen anion A according to the stoichiometric ratio in the process of preparing the layered lithium-rich oxide cathode material Li[Li _(1-2x)/3 M _x Mn _(2-x)/3 ]O ₂ , and prepare Li[Li _(1-2x)/3 M _x Mn _(2-x)/3 ]O _2-z A _z was obtained through solidification, drying and roasting.

The lithium-rich cathode material is Li[Li _0.17 Ni _0.25 Mn _0.58 ]O ₂ , Li[Li _0.20 Ni _0.1 Al _0.03 Co _0.13 Mn _0.54 ]O ₂ or Li[Li ₀₂ Co _0.4 Mn _0.4 ]O ₂ .

The lithium-rich cathode material doped with halogen anions is Li[Li ₀₁₇ Ni _0.25 Mn ₀₅₈ ]O _1.85 Cl _0.15 , Li[Li _0.22 Ni _0.05 Al _0.02 Co _0.1 Mn _0.61 ]O ₁₉₄ Br _0.06 or Li[Li _0.2 Co _0.4 Mn _0.4 ]O _1.98 I _0.02 .

The preparation method of the halogen anion-doped lithium-rich cathode material provided by the present invention is through the following steps:

1) Lithium salt (lithium acetate or lithium nitrate or lithium hydroxide), nickel, manganese or (and) cobalt salt (nitrate or acetate) and the salt of halogen anion A (ammonium salt or manganese salt or The salt formed with metal M) is prepared into an aqueous solution, wherein the mass ratio of the lithium salt is 3-8% in excess of the stoichiometric ratio; the total concentration of metal ions is 0.5-2 moles per liter; then add citric acid, citric acid and total metal ion moles The ratio is 2:1, adjust the pH of the mixture to 9 with ammonia water, and stir evenly;

2) spray drying the solution prepared in step 1) in a spray dryer to obtain a uniformly mixed precursor;

3) Transfer the precursor product obtained in step 2) to a crucible, and bake at 420-500° C. for 4-9 hours;

4) Grind the product obtained in step 3) and bake it at 700-900°C for 10-22 hours to obtain the product Li[Li _(1-2x)/3 M _x Mn _(2-x)/3 ]O _{2- z} A _z .

The source of the halogen anion is the ammonium salt, the manganese salt or the salt of the M element in the expression containing the halogen anion.

Described nickel, cobalt salt and manganese salt are their nitrate or acetate respectively.

The layered oxide cathode material Li[Li _(1-2x)/3 M _x Mn _(2-x)/3 ]O _2-z A _z obtained in the present invention can be directly used to manufacture lithium ion batteries.

The advantage of the present invention is, when the layered oxide Li[Li _(1-2x)/3 M _x Mn _(2-x)/3 ]O _2-z A _z material of halide anion doping is used as lithium ion battery cathode material 1) It can inhibit the oxygen precipitation of the material during the first charging process, thereby improving the first charge and discharge efficiency of the material; 2) The doped halogen anion stabilizes the structure of the material and inhibits the structural transformation of the material during the electrochemical cycle; 3 ) doping with halogen anions delays the drop of the voltage plateau to a certain extent. Therefore, the invention improves the electrochemical performance of the lithium-rich layered oxide cathode material, and has the characteristics of high initial charge and discharge efficiency, high capacity, good cycle performance, simple preparation process and good reproducibility.

Description of drawings

FIG. 1 is an X-ray diffraction (XRD) pattern of the Li[Li _0.17 Ni ₀₂₅ Mn _0.58 ]O _1.85 Cl _0.15 cathode material prepared in Example 1.

FIG. 2 is a transmission electron microscope (TEM) photo of the Li[Li _0.17 Ni _0.25 Mn _0.58 ]O ₁₈₅ Cl _0.15 cathode material prepared in Example 1.

3 is the discharge curve of the Li[Li ₀₁₇ Ni _0.25 Mn _0.58 ]O _1.85 Cl _0.15 positive electrode material prepared in Example 1 at a current density of 30 mA/g.

4 is the discharge capacity cycle curve of the Li[Li _0.22 Ni ₀₀₅ Al _0.02 Co _0.1 Mn _0.61 ]O _1.94 Br _0.06 positive electrode material prepared in Example 2 at a current density of 30 milliamperes per gram.

FIG. 5 is the discharge curve of the Li[Li _0.2 Co _0.4 Mn ₀₄ ]O _1.98 I ₀₀₂ cathode material prepared in Example 3 at a current density of 30 mA/g.

Detailed ways

The present invention can be embodied in the embodiments described below, but only for the purpose of illustration and not for limiting the invention.

Example 1

Preparation of Li[Li ₀₁₇ Ni _0.25 Mn ₀₅₈ ]O _1.85 Cl _0.15 :

Weigh 6.248 grams of CH ₃ COOLi 2H ₂ O, 3.111 grams of Ni(CH ₃ COO) ₂ 2H ₂ O, 6.229 grams of Mn(CH ₃ COO) ₂ 2H ₂ O and 0.7422 grams of MnCl ₂ 4H ₂ O, and prepare into 200 milliliters of aqueous solution, then add citric acid of 200 milliliters of 1.0 moles per liter, add ammoniacal liquor and adjust the pH of the mixed solution to 9, stir well; -217) to spray-dry to obtain a homogeneously mixed precursor; grind the obtained precursor into powder, transfer it to a crucible, and bake it at 480°C for 7.5 hours. After cooling, grind the material and place the ground material on After sintering in a muffle furnace at 900°C for 10 hours, the halogen anion-doped Li[Li ₀₁₇ Ni _0.25 Mn _0.58 ]O _1.85 Cl _0.15 material was finally prepared. Figure 1 is an X-ray diffraction (XRD) pattern of the prepared material, in which no diffraction peaks of other compounds appear, proving that the bulk crystal structure of the material has not been changed by doping ^Cl- . Fig. 2 is a transmission electron microscope (TEM) image of the prepared material, from which it can be seen that the material particles are spherical in shape, and the particle diameter is in the range of 100-200 nanometers.

The electrochemical performance test is as follows: the prepared halogen anion-doped lithium-rich material is used as the positive electrode material, metal lithium is used as the counter electrode, and a half-cell is assembled according to the conventional method, and the assembled battery is charged at a constant current at room temperature. Discharge test, the voltage range is: 2.0 ~ 4.8 volts. Figure 3 shows the discharge curve of the material at a current density of 30 mA/g. It can be seen from Figure 3 that the prepared material has a discharge capacity of 275.1mAh/g, which has a relatively high discharge specific capacity.

Example 2

Preparation of Li[Li ₀₂₂ Ni _0.05 Al _0.02 Co _0.1 Mn _0.61 ]O _1.94 Br _0.06 :

Change the mass of CH ₃ COOLi·2H ₂ O in Example 1 to 6.5456 grams, the mass of Ni(CH ₃ COO) ₂ ·2H ₂ O to 0.5807 grams, and the mass of Mn(CH ₃ COO) ₂ ·2H ₂ O to 7.4889 grams. The mass of added Co(CH ₃ COO) ₂ ·2H ₂ O was 1.2454g, the mass of NH ₄ Br was 0.2938g, and the mass of Al(NO ₃ ) ₃ ·9H ₂ O was 0.3751g. Others are the same as in Example 1, Li[Li ₀₂₂ Ni _0.05 Al _0.02 Co _0.1 Mn ₀₆₁ ]O _1.94 Br _0.06 material can be prepared. Figure 4 shows its electrochemical performance. At a current density of 30 mA/g, the Br-doped Li[Li _0.22 Ni _0.05 Al _0.02 Co _0.1 Mn _0.61 ]O _1.94 Br _0.06 material has a specific discharge capacity of 223.0 after 30 weeks mAh per gram, excellent cycle performance.

Example 3

Preparation of Li[Li _0.2 Co _0.4 Mn _0.4 ]O _1.98 I _0.02 material:

In Example 1, Ni(CH ₃ COO) ₂ ·2H ₂ O and MnCl ₂ ·4H ₂ O were removed. The mass of Mn(CH ₃ COO) ₂ ·2H ₂ O was changed to 4.902 g, the mass of Co(CH ₃ COO) ₂ ·2H ₂ O was added to be 4.9816 g, and the mass of LiI was 0.1879 g. The mass of CH ₃ COOLi·2H ₂ O was changed to 6.3246 g, and the others were the same as in Example 1, so that Li[Li _0.2 Co _0.4 Mn ₀₄ ]O _1.98 I _0.02 material could be prepared. Figure 5 shows the charge-discharge curves of the first cycle of the material prepared in this example at a current density of 30 milliamperes per gram. It can be seen from the figure that after doping with I, the material also has a higher discharge specific capacity.

Claims (8)

1. A lithium-rich cathode material doped with halogen anions, characterized in that its composition expression is: Li[Li _(1-2x)/3 M _x Mn _(2-x)/3 ]O _2-z A _z , M is at least one or a combination of Co, Ni, Al, Mg, Zn, Ga, B, Zr, Ti, Ca, Ce, Y, Nb elements, A = one of Cl, Br or I or Its combination, 0<x<0.5;0<z≤0.5; when M=Ni, Co or a combination thereof and A=Cl, x≠0.2. 2. The lithium-rich cathode material doped with halogen anions according to claim 1, characterized in that M is an element of Co, Ni, Al, Mg, Zn, Ga, B, Zr, Ti, Ca, Ce, Y, Nb one or a combination of them. 3. The lithium-rich cathode material doped with halogen anions according to claim 1, characterized in that the lithium-rich cathode material is Li[Li ₀₁₇ Ni _0.25 Mn ₀₅₈ ]O ₂ , Li[Li _0.20 Ni _0.1 Al _0.03 Co _0.13 Mn _0.54 ]O ₂ or Li[Li _0.2 Co _0.4 Mn _0.4 ]O ₂ . 4. The lithium-rich cathode material doped with halogen anions according to claim 1, characterized in that it is Li[Li _0.17 Ni _0.25 Mn _0.58 ]O _1.85 Cl ₀₁₅ Li[Li ₀₂₂ Ni _0.05 Al ₀₀₂ Co _0.1 Mn ₀₆₁ ] O _1.94 Br ₀₀₆ or Li[Li _0.2 Co ₀₄ Mn _0.4 ]O _1.98 I ₀₀₂ . 5. The preparation method of the lithium-rich cathode material doped with halogen anions as claimed in claim 1, characterized in that it is through the following steps: 1) Lithium salt or lithium hydroxide, nickel, manganese, or cobalt salt and halide anion A are formulated into an aqueous solution according to the stoichiometric ratio, wherein the mass ratio of the lithium salt is 3 to 8% in excess of the stoichiometric ratio; the total concentration of metal ions 0.5-2 moles per liter; then add citric acid, the molar ratio of citric acid and total metal ions is 2:1, adjust the pH of the mixed solution to 9 with ammonia water, and stir evenly; 2) spray drying the solution prepared in step 1) in a spray dryer to obtain a uniformly mixed precursor; 3) Transfer the precursor product obtained in step 2) to a crucible, and bake at 420-500° C. for 4-9 hours; 4) Grind the product obtained in step 3) and bake it at 700-900°C for 10-22 hours to obtain the product Li[Li _(1-2x)/3 M _x Mn _(2-x)/3 ]O _{2- z} A _z . 6. The preparation method according to claim 5, characterized in that the source of the halogen anion is an ammonium salt containing the halogen anion, a manganese salt or a salt of the M element in the expression. 7. the preparation method according to claim 5 is characterized in that described nickel, cobalt salt and manganese salt are their nitrate or acetate respectively. 8. The lithium-rich cathode material according to any one of claims 1-4 is used to manufacture lithium-ion batteries.