CN104466160A - Preparation method of lithium enriched ternary system nanometer material - Google Patents

Abstract

The invention discloses a preparation method of a lithium-rich ternary system nano material, and the prepared lithium-rich ternary system Li[Li _0.2 Mn _0.54 Ni _0.13 Co _0.13 ]O ₂ nano material can be used as a positive electrode material of a lithium ion battery. The method synthesizes an electrode material through a sol-gel method, and the preparation method includes the following steps: Weigh the stoichiometric complexing agent ethylenediaminetetraacetic acid (EDTA) and dissolve it in ammonia water, stir evenly to form a transparent solution A; According to the molar ratio of ions Li ⁺ :Mn ²⁺ :Co ²⁺ :Ni ²⁺ =1.26:0.54:0.13:0.13, weigh the corresponding salt and dissolve it in deionized water to form pink solution B; Mix solution A and solution B under stirring in a water bath at 80°C to make the complexation reaction fully occur, and add complexing agent citric acid after stirring for 2 hours; Evaporate the solvent at 80°C to form a wet gel, dry at 100°C for 24 hours, pre-calcine after grinding, and heat-treat at high temperature in a muffle furnace for a certain period of time to obtain a lithium-rich ternary material.

Description

Preparation method of lithium-rich ternary nanomaterial

technical field

The invention relates to a preparation method of a lithium-rich ternary system nano material, and the prepared lithium-rich ternary system Li[Li _0.2 Mn _0.54 Ni _0.13 Co _0.13 ]O ₂ nano material can be used as a positive electrode material of a lithium ion battery.

Background technique

Lithium-ion batteries are key energy storage devices for portable consumer electronics and new energy industries including electric vehicles. The main factor limiting its development is the cathode material. At present, lithium iron phosphate is generally used as the cathode material of commercialized lithium-ion batteries. Its theoretical specific capacity is only 170mAh/g, and its energy density is low, which limits the further improvement of the specific capacity of lithium-ion batteries. It is difficult to meet the needs of future electronic products and power batteries. Requirements for high-capacity lithium-ion batteries. In order to overcome the shortcomings of such materials, people are looking for new cathode materials with high capacity. In recent years, ternary materials have attracted extensive attention from researchers because of their high operating voltage and objective specific capacity at low rates, and they have broad prospects for future power battery applications. The solid _solution material _{xLi 2 MnO 3 ·} (1 _- x) _{LiNi 1/3 Co 1/3} Mn _{1/3 O 2} Higher specific capacity (>250mAh/g) has become the focus of research. Compared with conventional layered materials, a certain amount of lithium is contained in the transition metal layer, and this part of lithium forms an ordered arrangement with other transition metal ions , often referred to as lithium-rich materials. When the value of x is 0.5, the lithium-rich material Li[Li _0.2 Mn _0.54 Ni _0.13 Co _0.13 ]O ₂ has been extensively studied with a high discharge specific capacity of 280mAh/g at a room temperature of 2.0~4.8V and a current density of 20mA/g.

At present, the main methods for synthesizing lithium-rich ternary Li[Li _0.2 Mn _0.54 Ni _0.13 Co _0.13 ]O ₂ materials are solid phase method, co-precipitation method and sol-gel method. The solid-phase method is to weigh the raw materials according to the stoichiometric ratio, put them in a ball mill to obtain a precursor through ball milling, and obtain a lithium-rich ternary material after heat treatment in air. Although this method is suitable for large-scale production, the obtained material particles are relatively large. , The uneven morphology prevents the electrolyte from entering the particles, resulting in poor high-rate electrochemical performance of the material. In addition, the ball milling method consumes high energy; the co-precipitation method is to configure the metal salt of manganese, nickel and cobalt into a solution, and select a suitable co-precipitation method. Precipitating agent, forming hydroxide, precipitation and drying, mixing with lithium salt and heat treatment to obtain lithium-rich ternary system materials. In this method, the adjustment of Ph is difficult to accurately control, resulting in uneven nucleation speed during the co-precipitation process, and the synthesized material particles In order to overcome the defects in the above synthesis methods, the present invention adopts the sol-gel method to synthesize lithium-rich ternary system Li[Li _0.2 Mn _0.54 Ni _0.13 Co _0.13 ]O ₂ cathode material.

When synthesizing multi-metal ion oxides, due to the different complexing abilities of complexing agents to metal ions, the uniformity of the prepared precursor composition, the morphology and particle uniformity of the sintered material, and the electrical conductivity of the material will be affected when a single complexing agent is used. The chemical properties are affected to varying degrees, and the method of using double complexing agents can effectively improve the adverse effects of a single complexing agent. Literature (Zhao Xueling et al. Acta Inorganic Chemistry. 2013, Vol. 29, No. 5, 1013-1018) separately used citric acid (CA) and ethylenediaminetetraacetic acid (EDTA) as complexing agents to synthesize lithium-rich binary layers Like Li[Li _0.2 Ni _0.2 Mn _0.6 ]O ₂ materials, it was found that when EDTA was used as a complexing agent to synthesize the material, the particle size distribution of the material was not uniform during the sintering process, and the electrochemical performance was poor, while CA was used as a complexing agent. A binary layered material with better electrochemical performance is obtained, but the Ph value needs to be precisely adjusted during the synthesis process to prevent the precipitation of the gel formed during the evaporation of the solvent, and the material particles are agglomerated with different particle sizes. Therefore, the present invention finds a new way to synthesize lithium-rich ternary materials by using EDTA and CA double complexing agent, and at the same time makes certain improvements in the pre-calcination process to obtain electrode materials with uniform particles.

Contents of the invention

The main idea of the present invention is: firstly, by adjusting the ratio of EDTA and CA, a uniform lithium-rich ternary gel precursor is synthesized, and then carbonized in an inert atmosphere to form a metal oxide with uniform particles, and finally sintered in air A lithium-rich ternary material with uniform appearance, uniform particles and good electrochemical performance is obtained.

One of the purposes of the present invention is to use the sol-gel method to complex metal ions using double complexing agents to limit the growth of the particle size of the material and control the particle morphology, thereby improving the high-rate performance of the material and obtaining electrochemical performance. Excellent lithium-rich ternary electrode material.

The second object of the present invention is to provide a lithium-ion battery positive electrode material that is simple and feasible to operate, requires low raw material prices, low production costs, and is environmentally friendly.

In order to achieve the above object, the present invention adopts the following technical solutions to achieve.

The preparation method of lithium-rich ternary nanomaterials comprises the following steps:

(1) Weigh 0.05mol of complexing agent ethylenediaminetetraacetic acid (EDTA) as the first complexing agent and dissolve it in 50ml of dilute ammonia water, stir well to form a transparent solution A with a concentration of 1mol/L;

(2) According to the molar ratio of ions Li ⁺ :Mn ²⁺ :Co ²⁺ :Ni ²⁺ =1.26:0.54:0.13:0.13, weigh the corresponding salt and dissolve it in deionized water to form pink solution B;

(3) Mix solution A and solution B under stirring in a water bath at 80°C to make the complexation reaction fully occur. After stirring for 2 hours, add citric acid as the second complexing agent, wherein the molar ratio of ethylenediaminetetraacetic acid to citric acid is 1 : 1～2, the concentration of citric acid is 0.1～0.2mol/L;

(4) Evaporate the solvent at 80°C to form a wet gel, dry at 100°C for 24 hours, first pre-calcine in an atmosphere furnace at a temperature of 400°C, and pre-calcine for 3 to 6 hours; then calcinate in a muffle furnace at a temperature of 700 to 900° C., and the calcination time is 6-24 hours to obtain lithium-rich ternary system Li[Li _0.2 Mn _0.54 Ni _0.13 Co _0.13 ]O ₂ nanomaterials.

Preferably, the soluble manganese source in step (2) is one of manganese nitrate, manganese acetate, manganese sulfate, and manganese chloride; the soluble nickel source is nickel nitrate, nickel acetate, nickel sulfate, and nickel chloride. A kind of; Described soluble cobalt source is a kind of in cobalt nitrate, cobalt acetate, cobalt sulfate, cobalt chloride; Described soluble lithium source is a kind of in lithium nitrate, lithium acetate, lithium hydroxide, lithium carbonate.

Preferably, the second complexing agent in step (3) can be replaced by tartaric acid, oxalic acid or succinic acid.

Preferably, the pre-firing atmosphere in step (4) is Ar or N ₂ or a mixed gas of Ar and N ₂ .

As a preference, the heating rate from room temperature to sintering temperature during the sintering process in step (4) is 2°C/min

The beneficial effects of the present invention are:

1) The lithium-rich ternary material synthesized by the sol-gel method has uniform chemical composition, high purity, and small particles, which is conducive to the formation and growth of crystals during the material heat treatment process, and can reduce the reaction temperature and shorten the reaction time;

2) Using ethylenediaminetetraacetic acid (EDTA) and citric acid as a double complexing agent can achieve in-situ growth of metal ions, limiting the increase in particle size of the material, and at the same time, the two are decomposed into NH ₃ and CO during heat treatment ₂ discharge, which can effectively improve the dispersion of material particles;

3) By improving the particle size and morphology of the material, the electrochemical performance of the material at high rates can be effectively improved, and the cycle performance and battery life of the battery can be increased.

Description of drawings

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is the X-ray diffraction (XRD) spectrum of the lithium-rich ternary system Li[Li _0.2 Mn _0.54 Ni _0.13 Co _0.13 ]O ₂ nanometer cathode material of the embodiment of the preparation method of the lithium-rich ternary nanomaterial of the present invention;

Fig. 2 is a scanning electron microscope spectrum of the lithium-rich ternary system Li[Li _0.2 Mn _0.54 Ni _0.13 Co _0.13 ]O ₂ nanometer positive electrode material of the embodiment of the preparation method of the lithium-rich ternary nanomaterial of the present invention;

Fig. 3 is the electrochemical cycle curve of the lithium-rich ternary system Li[Li _0.2 Mn _0.54 Ni _0.13 Co _0.13 ]O ₂ nanometer cathode material according to the embodiment of the preparation method of the lithium-rich ternary nanomaterial of the present invention.

Detailed ways

The following is the specific experimental process for the synthesis of lithium-rich ternary Li[Li _0.2 Mn _0.54 Ni _0.13 Co _0.13 ]O ₂ nanometer positive electrode materials, in order to further describe the present invention in detail.

Example 1

Weigh 0.05mol complexing agent ethylenediaminetetraacetic acid (EDTA) and dissolve it in 50ml dilute ammonia water, stir well to form 1mol/L transparent solution A;

According to the molar ratio of ions Li ⁺ : Mn ²⁺ : Co ²⁺ : Ni ²⁺ =1.26:0.54:0.13:0.13, weigh 63mmol of lithium acetate, 27mmol of manganese acetate, 6.5mmol of cobalt acetate and 6.5mmol of nickel acetate in the A pink solution B is formed in deionized water;

Mix solution A and solution B under stirring in a water bath at 80°C to make the complexation reaction fully occur. After stirring for 2 hours, add 75 mmol of complexing agent citric acid, wherein the molar ratio of double complexing agent EDTA to citric acid is 1:1.5, citric acid The concentration is 1.5mol/L;

Evaporate the solvent at 80°C to form a wet gel, dry at 100°C for 24 hours, pre-calcine in an atmosphere furnace at a temperature of 400°C for 4 hours, and then calcinate in a muffle furnace at a temperature of 800°C for 10 hours , to obtain lithium-rich ternary materials.

the

Example 2

(1) Weigh 0.05mol complexing agent ethylenediaminetetraacetic acid (EDTA) and dissolve it in 50ml dilute ammonia water, stir well to form 1mol/L transparent solution A;

(2) According to the molar ratio of ions Li ⁺ :Mn ²⁺ :Co ²⁺ :Ni ²⁺ =1.26:0.54:0.13:0.13, weigh 63mmol of lithium acetate, 27mmol of manganese acetate, 6.5mmol of cobalt acetate and 6.5mmol of nickel acetate in A pink solution B is formed in deionized water;

(3) Mix solution A and solution B under stirring in a water bath at 80°C to make the complexation reaction fully occur. After stirring for 2 hours, add 75 mmol of complexing agent citric acid, wherein the molar ratio of double complexing agent EDTA to citric acid is 1:2, lemon The acid concentration is 2mol/L;

(4) Evaporate the solvent at 80°C to form a wet gel, dry at 100°C for 24 hours, first pre-calcine in an atmosphere furnace at a temperature of 400°C, and pre-calcine for 4 hours; then calcinate in a muffle furnace at a temperature of 900°C, and calcining time of 10h, the lithium-rich ternary system material was obtained.

the

Example 3

(1) Weigh 0.05mol complexing agent ethylenediaminetetraacetic acid (EDTA) and dissolve it in 50ml dilute ammonia water, stir well to form 1mol/L transparent solution A;

(2) According to the molar ratio of ions Li ⁺ :Mn ²⁺ :Co ²⁺ :Ni ²⁺ =1.26:0.54:0.13:0.13, weigh 63mmol of lithium acetate, 27mmol of manganese acetate, 6.5mmol of cobalt acetate and 6.5mmol of nickel acetate in A pink solution B is formed in deionized water;

(3) Mix solution A and solution B under stirring in a water bath at 80°C to make the complexation reaction fully occur. After stirring for 2 hours, add 75 mmol of complexing agent citric acid, wherein the molar ratio of double complexing agent EDTA to citric acid is 1:1, lemon The acid concentration is 1mol/L;

(4) Evaporate the solvent at 80°C to form a wet gel, dry at 100°C for 24 hours, first pre-calcine in an atmosphere furnace at a temperature of 400°C, and pre-calcine for 6 hours; then calcinate in a muffle furnace at a temperature of 800°C, and calcining time 10h, the lithium-rich ternary system material was obtained.

the

Example 4

(1) Weigh 0.05mol complexing agent ethylenediaminetetraacetic acid (EDTA) and dissolve it in 50ml dilute ammonia water, stir well to form 1mol/L transparent solution A;

(2) According to the molar ratio of ions Li ⁺ :Mn ²⁺ :Co ²⁺ :Ni ²⁺ =1.26:0.54:0.13:0.13, weigh 63mmol of lithium acetate, 27mmol of manganese acetate, 6.5mmol of cobalt acetate and 6.5mmol of nickel acetate in A pink solution B is formed in deionized water;

(3) Mix solution A and solution B under stirring in a water bath at 80°C to make the complexation reaction fully occur. After stirring for 2 hours, add 75 mmol of complexing agent citric acid, wherein the molar ratio of double complexing agent EDTA to citric acid is 1:1.5, lemon The acid concentration is 1.5mol/L;

(4) Evaporate the solvent at 80°C to form a wet gel, dry at 100°C for 24 hours, first pre-calcine in an atmosphere furnace at a temperature of 400°C, and pre-calcine for 6 hours; then calcinate in a muffle furnace at a temperature of 800°C, and calcining time is After 24 hours, a lithium-rich ternary material was obtained.

the

Example 5

(1) Weigh 0.05mol complexing agent ethylenediaminetetraacetic acid (EDTA) and dissolve it in 50ml dilute ammonia water, stir well to form 1mol/L transparent solution A;

(2) According to the molar ratio of ions Li ⁺ :Mn ²⁺ :Co ²⁺ :Ni ²⁺ +=1.26:0.54:0.13:0.13, weigh 63mmol lithium acetate, 27mmol manganese acetate, 6.5mmol cobalt acetate, 6.5mmol nickel acetate solution Form pink solution B in deionized water;

(3) Mix solution A and solution B under stirring in a water bath at 80°C to make the complexation reaction fully occur. After stirring for 2 hours, add 75 mmol of complexing agent citric acid, wherein the molar ratio of double complexing agent EDTA to citric acid is 1:1.5, lemon The acid concentration is 1.5mol/L;

(4) Evaporate the solvent at 80°C to form a wet gel, dry at 100°C for 24 hours, first pre-calcine in an atmosphere furnace at a temperature of 400°C, and pre-calcine for 4 hours; then calcinate in a muffle furnace at a temperature of 900°C, and calcining time of After 24 hours, a lithium-rich ternary material was obtained.

the

Example 6

(1) Weigh 0.05mol complexing agent ethylenediaminetetraacetic acid (EDTA) and dissolve it in 50ml dilute ammonia water, stir well to form 1mol/L transparent solution A;

(2) According to the molar ratio of ions Li ⁺ :Mn ²⁺ :Co ²⁺ :Ni ²⁺ =1.26:0.54:0.13:0.13, weigh 63mmol of lithium acetate, 27mmol of manganese acetate, 6.5mmol of cobalt acetate and 6.5mmol of nickel acetate in A pink solution B is formed in deionized water;

(3) Mix solution A and solution B under stirring in a water bath at 80°C to make the complexation reaction fully occur. After stirring for 2 hours, add 75 mmol of complexing agent citric acid, wherein the molar ratio of double complexing agent EDTA to citric acid is 1:2, lemon The acid concentration is 2mol/L;

(4) Evaporate the solvent at 80°C to form a wet gel, dry at 100°C for 24 hours, first pre-calcine in an atmosphere furnace at a temperature of 400°C, and pre-calcine for 4 hours; then calcinate in a muffle furnace at a temperature of 700°C, and calcining time of 10h, the lithium-rich ternary system material was obtained.

In conjunction with the accompanying drawings, the electrochemical performance of the prepared lithium-rich ternary material is illustrated with Example 1

Fig. 1 is the X-ray diffraction (XRD) pattern of the lithium-rich ternary system material prepared in Example 2; its abscissa is the measurement angle of X-ray diffraction, and the ordinate is the diffraction peak intensity of the material at this diffraction angle . From the analysis of the spectral results, it can be seen that the synthesized material is a layered Li[Li _0.2 Mn _0.54 Ni _0.13 Co _0.13 ]O ₂ ternary material without other impurity phases, and has high crystallinity and purity.

Fig. 2 is the SEM spectrum of the lithium-rich Li[Li _0.2 Mn _0.54 Ni _0.13 Co _0.13 ]O ₂ ternary material prepared in Example 1. The particle size of the material is about 100 nm, and the shape is uniform.

3 is a cycle curve of the lithium-rich Li[Li _0.2 Mn _0.54 Ni _0.13 Co _0.13 ]O ₂ ternary material prepared in Example 1. It can be seen from the figure that when the current density is 40 mA/g, the specific capacity of the material is maintained at about 240mAh/g after 40 cycles, showing good electrochemical performance.

The embodiments of the present invention described above are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims (5)

1. A method for preparing lithium-rich ternary nanomaterials, comprising the following steps: (1) Weigh 0.05mol of complexing agent ethylenediaminetetraacetic acid (EDTA) as the first complexing agent and dissolve it in 50ml of dilute ammonia water, stir well to form a transparent solution A with a concentration of 1mol/L; (2) According to the molar ratio of ions Li ⁺ :Mn ²⁺ :Co ²⁺ :Ni ²⁺ =1.26:0.54:0.13:0.13, weigh the corresponding salt and dissolve it in deionized water to form pink solution B; (3) Mix solution A and solution B under stirring in a water bath at 80°C to make the complexation reaction fully occur. After stirring for 2 hours, add citric acid as the second complexing agent, wherein the molar ratio of ethylenediaminetetraacetic acid to citric acid is 1 : 1～2, the concentration of citric acid is 0.1～0.2mol/L; (4) Evaporate the solvent at 80°C to form a wet gel, dry at 100°C for 24 hours, first pre-calcine in an atmosphere furnace at a temperature of 400°C, and pre-calcine for 3 to 6 hours; then calcinate in a muffle furnace at a temperature of 700 to 900° C., and the calcination time is 6-24 hours to obtain lithium-rich ternary system Li[Li _0.2 Mn _0.54 Ni _0.13 Co _0.13 ]O ₂ nanomaterials. 2. The preparation method according to claim 1, characterized in that: the soluble manganese source in step (2) is one of manganese nitrate, manganese acetate, manganese sulfate, and manganese chloride; the soluble nickel source is One of nickel nitrate, nickel acetate, nickel sulfate, nickel chloride; the soluble cobalt source is one of cobalt nitrate, cobalt acetate, cobalt sulfate, cobalt chloride; the soluble lithium source is lithium nitrate, acetic acid One of lithium, lithium hydroxide, and lithium carbonate. 3. The preparation method according to claim 1, characterized in that: the second complexing agent in step (3) can be replaced by tartaric acid or oxalic acid or succinic acid. 4. The preparation method according to claim 1, characterized in that the heating rate from room temperature to sintering temperature during the sintering process in step (4) is 2°C/min. 5. The preparation method according to claim 1, characterized in that: the pre-firing atmosphere in step (4) is Ar or N ₂ or a mixed gas of Ar and N ₂ . the