CN100591624C - Co-precipitation-combustion synthesis method of nickel cobalt lithium manganese oxide - Google Patents

Abstract

The invention discloses a co-precipitation-combustion synthesis method of lithium nickel cobalt manganese oxide. (1) With nickel, cobalt, manganese acetate or nitrate as transition metal source, ammonia water as complexing agent, H ₂ C ₂ O ₄ , (NH ₄ ) ₂ C ₂ O ₄ , (NH ₄ ) ₂ CO ₃ or NH ₄ HCO ₃ is a precipitating agent, and synthesizes Ni-Co-Mn composite carbonate or oxalate precursor by co-precipitation method; (2) the above-mentioned Ni-Co-Mn composite carbonate or oxalate Dry the suspension directly, add lithium nitrate or lithium acetate and a small amount of water or ethanol to adjust the rheological phase state; (3) put the above-mentioned materials in the rheological phase state in an electric furnace heated to 400-600 ° C and constant temperature for Combustion synthesis reaction; (4) Tempering the above reaction product at 600-1200° C. to obtain _LiNix Co _y Mn _1-xy O ₂ anode active material for lithium ion battery. The invention has the advantages of simple process, easy operation, water saving and energy saving, environmental protection, and the synthetic material has spherical or quasi-spherical appearance, high specific capacity, good cycle performance and the like.

Description

Co-precipitation-combustion synthesis method of nickel cobalt lithium manganese oxide

technical field

The invention relates to a method for synthesizing positive electrode materials _of lithium ion batteries, in particular to a coprecipitation-combustion synthesis method of _{LiNixCoyMn1 -xyO2 .}

Background technique

The vast majority of existing commercial lithium-ion batteries use lithium cobalt oxide as the positive electrode material. Although this material has the advantages of easy synthesis, stable performance, and high capacity, the cobalt required for its synthesis has serious disadvantages such as high price, high toxicity, and lack of resources. The development of cobalt-less or cobalt-free cathode materials has become a direction for the development of cathode materials for lithium-ion batteries.

LiNi _x Co _y Mn _1-xy O ₂ is one of the most promising new cathode materials developed in recent years to replace lithium cobalt oxide. At present, the methods for synthesizing LiNi _x Co _y Mn _1-xy O ₂ mainly include co-precipitation method, sol-gel method, emulsion method, high-temperature solid-phase method and combustion method, among which the co-precipitation method is to synthesize homogeneous LiNi _x Co The commonly used method of _y Mn _1-xy O ₂ has a low synthesis temperature and can obtain spherical or quasi-spherical particles, but because it is difficult to completely precipitate transition metal ions through a precipitant, the process of filtering and washing It is easy to cause the loss of transition metal ions in the process, and the existing co-precipitation method needs to synthesize the precursor under the protection of the atmosphere. The stirring speed, pH value, solution concentration, etc. have a great influence on the electrochemical performance of the synthesized product, and the equipment requirements High, it is difficult to industrialize production. The high-temperature solid-phase method has low equipment requirements, but because the mixing of raw materials cannot achieve uniformity at the molecular level, it generally needs to be calcined at a higher temperature for a long time at a constant temperature, which consumes a lot of energy in production, and the synthesized positive electrode material particles are irregular and prone to Heterogeneous phase, it is difficult to synthesize homogeneous _LiNix Co _y Mn _1-xy O ₂ ; the combustion method has a simple process, low equipment requirements, and short synthesis time, but the synthetic product particles are irregular and easily produce impurities such as NiO.

Contents of the invention

The purpose of the present invention is to provide a method with simple operation, short synthesis time, low synthesis temperature, suitable for industrial production of spherical or spherical lithium ion battery cathode materials, i.e. coprecipitation of LiNi _x Co _y Mn _1-xy O ₂ - Combustion synthesis method, the synthesized product has a layered structure of α- _NaFeO2 .

Concrete steps of the present invention are:

1) With nickel, cobalt, manganese acetate or nitrate as transition metal source, the molar ratio is n(Ni):n(Co):n(Mn)=x:y:(1-x-y), 0 <x<1, 0≤y<0.5, x+y<1; accurately weigh the material, add an appropriate amount of distilled water to make a mixed acetate or mixed nitrate solution of nickel, cobalt, and manganese;

2) Using ammonia water as a complexing agent, add ammonia water with a concentration of 1-5M to the above solution to make a complex solution. The amount of ammonia water is the molar ratio n(NH ₃ H ₂ O):n(Ni+Co+ Mn)=1～7:1, control the pH value between 5～9;

3) Add precipitant H ₂ C ₂ O ₄ , (NH ₄ ) ₂ C ₂ O ₄ , (NH ₄ ) ₂ CO ₃ or NH ₄ HCO ₃ to the above complex solution, the amount of precipitant is molar ratio n( C ₂ O ₄ ^2- ) or n(CO ₃ ^2- ):n(Ni+Co+Mn)=1.05～1.2:1, make it in 25～80℃, stirring speed is 300-1000r/min water bath reactor React in medium for 0.5 to 5 hours to obtain Ni-Co-Mn composite carbonate or composite oxalate;

4) adjust the pH of the above-mentioned suspension containing Ni-Co-Mn composite carbonate or composite oxalate with ammonia water=7～9, dry at 100°C to obtain the composite carbonate or composite carbonate of Ni-Co-Mn Mixtures of oxalates with ammonium acetate or ammonium nitrate;

5) Lithium nitrate or lithium acetate is used as the lithium source, and the molar ratio n(Li):n(Ni+Co+Mn)=1.05～1.15:1, accurately weigh lithium nitrate or lithium acetate, and add it to the above mixture, And add a small amount of water or ethanol to adjust the rheological phase;

7) placing the above-mentioned material in a rheological phase state in an electric furnace heated to 400-600° C. and constant temperature, so that a self-propagating combustion reaction occurs to obtain a synthetic product;

8) Tempering the synthesis product of the above combustion reaction at 700-1200° C. for 10-25 hours to obtain a positive electrode material for a lithium-ion battery with good layered structure and electrochemical performance.

The synthesized product is a spherical or quasi-spherical powder material.

The invention has the following advantages and effects: when the precursor is prepared by the co-precipitation method, the reaction substance is dissolved in distilled water to form a mixed solution, which realizes uniform mixing at the molecular level. Nickel-cobalt-manganese composite carbonate or oxalate can be quickly synthesized by carbonate or oxalate co-precipitation, and the synthesized nickel-cobalt-manganese composite carbonate or oxalate has good chemical stability and has The spherical or spherical shape lays a good foundation for the synthesis of spherical or spherical positive electrode materials. The direct drying process eliminates the loss of components caused by the co-precipitation method due to washing, and saves a lot of washing water. The NH ₄ ⁺ and acetate and nitrate retained in the material can undergo a combustion reaction under certain conditions, providing fuel for combustion synthesis. The rheological phase mixing process is used to facilitate the uniform mixing of lithium salts and precursors. The low-temperature self-propagating combustion method not only makes full use of the acetate or nitrate left in the synthesis of the precursor, but also helps shorten the synthesis time.

The invention not only overcomes the shortcomings of the traditional co-precipitation method that requires repeated filtration and washing to cause the loss of useful components and large water consumption, but also makes up for the irregular shape of the positive electrode material particles synthesized by the simple combustion method and the solid-phase synthesis method and is prone to impurity. Insufficient, it has the advantages of simple process, easy operation, water saving and energy saving, green and environmental protection, and the synthetic material has spherical or spherical shape, high specific capacity and good cycle performance.

Description of drawings

Fig. 1 is an X-ray diffraction pattern of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ prepared in the present invention.

Fig. 2 is a scanning electron micrograph of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ prepared in the present invention.

Fig. 3 is a charge-discharge curve diagram of 10 cycles of a battery assembled with LiNi _1/3 Co _1/3 Mn _1/3 O ₂ prepared by the present invention as the positive electrode active material.

Detailed ways:

Example:

Using Ni(CH ₃ COO) ₂ ·4H ₂ O, Co(CH ₃ COO) ₂ ·4H ₂ O, Mn(CH ₃ COO) ₂ ·4H ₂ O, lithium nitrate as main raw materials, ammonia water as complexing agent, and H ₂ C ₂ O ₄ ·H ₂ O was used as precipitant, and LiNi _1/3 Co _1/3 Mn _1/3 O ₂ was synthesized by coprecipitation-combustion method.

Steps:

1. According to n(Ni):n(Co):n(Mn) (molar ratio) = 1:1:1, accurately weigh Ni(CH ₃ COO) ₂ 4H ₂ O, Co(CH ₃ COO) ₂ 4H ₂ O and Mn(CH ₃ COO) ₂ 4H ₂ O, add appropriate amount of distilled water to make a mixed solution with a concentration of 1M;

2. Add ammonia water to the above mixed solution to make a complex solution.

3. According to the molar ratio n(C ₂ O ₄ ^2- ):n(Ni+Co+Mn)=1.1:1, accurately weigh H ₂ C ₂ O ₄ ·H ₂ O, grind it into powder with a mortar and add it to In the above complex solution.

4. Stir at a speed of 600r/min in a water bath reactor at 40°C, and react for 30nm.

5. Adjust the pH to 8.5 with ammonia water, age for 10nim, and then dry at 100°C to obtain a mixture of nickel-cobalt-manganese compound oxalate and ammonium acetate.

6. According to the molar ratio n(Li):n(Ni+Co+Mn)=1.1:1, accurately weigh lithium nitrate, mix it with the above-mentioned mixture of nickel-cobalt-manganese compound oxalate and ammonium acetate and add a small amount of Water is adjusted into a rheological phase;

7. Put the above-mentioned materials in the rheological phase state in an electric furnace heated to 500°C and constant temperature, so that a series of reactions such as dehydration, smoking, ignition, and combustion will occur in the electric furnace. The reaction was complete within 15 minutes.

8. Collect the reaction product, grind it finely, put it into an alumina ceramic crucible after passing through a 50-mesh sieve, put it in an electric furnace, and temper it at 800°C for 15 hours, and then cool it with the furnace.

9. After cooling, the synthesized product was crushed and passed through a 300-mesh sieve to obtain LiNi _1/3 Co _1/3 Mn _1/3 O ₂ with α-NaFeO ₂ type layered structure and good electrochemical performance.

Claims (4)

1, a kind of co-precipitation-combustion synthesis method of lithium nickel cobalt manganate, is characterized in that concrete steps are: 1) With nickel, cobalt, manganese acetate or nitrate as transition metal source, the molar ratio is n(Ni):n(Co):n(Mn)=x:y:(1-x-y), 0 <x<1, 0≤y<0.5, x+y<1; accurately weigh the material, add an appropriate amount of distilled water to make a mixed acetate or mixed nitrate solution of nickel, cobalt, and manganese; 2) Using ammonia water as a complexing agent, add ammonia water with a concentration of 1-5M to the above solution to make a complex solution. The amount of ammonia water is the molar ratio n(NH ₃ H ₂ O):n(Ni+Co+ Mn)=1～7:1, control the pH value between 5～9; 3) Add precipitant H ₂ C ₂ O ₄ , (NH ₄ ) ₂ C ₂ O ₄ , (NH ₄ ) ₂ CO ₃ or NH ₄ HCO ₃ to the above complex solution, the amount of precipitant is molar ratio n( C ₂ O ₄ ^2- ) or n(CO ₃ ^2- ):n(Ni+Co+Mn)=1.05～1.2:1, make it in 25～80℃, stirring speed is 300-1000r/min water bath reactor React in medium for 0.5 to 5 hours to obtain Ni-Co-Mn composite carbonate or composite oxalate; 4) adjust the pH of the above-mentioned suspension containing Ni-Co-Mn composite carbonate or composite oxalate with ammonia water=7～9, dry at 100°C to obtain the composite carbonate or composite carbonate of Ni-Co-Mn Mixtures of oxalates with ammonium acetate or ammonium nitrate; 5) Lithium nitrate or lithium acetate is used as the lithium source, and the molar ratio n(Li):n(Ni+Co+Mn)=1.05～1.15:1, accurately weigh lithium nitrate or lithium acetate, and add it to the above mixture, And add a small amount of water or ethanol to adjust the rheological phase; 7) placing the above-mentioned rheological material in an electric furnace heated to 400-600°C and constant temperature, so that a self-propagating combustion reaction occurs to obtain a synthetic product; 8) Tempering the synthesis product of the above combustion reaction at 700-1200° C. for 10-25 hours to obtain a positive electrode material for a lithium-ion battery with good layered structure and electrochemical performance. 2. The synthesis method according to claim 1, characterized in that the synthesized product is LiNi _x Co _y Mn _1-xy O ₂ with α-NaFeO ₂ layered structure, 0<x<1, 0≤y <0.5, x+y<1. 3. The synthetic method according to claim 1, characterized in that the synthesized product is a spherical powder material. 4. The synthetic method according to claim 1, characterized in that the synthesized product is a spherical powder material.