CN110563052A - preparation method of carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide positive electrode material - Google Patents

Abstract

The invention discloses a preparation method of carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide positive electrode material, which belongs to the technical field of modified lithium nickel manganese oxide positive electrode material. The preparation method is: (1) Weigh lithium carbonate, manganese dioxide and nickel oxide, add ethanol or water, grind and mix, dry and sinter to obtain lithium nickel manganese oxide cathode material; (2) Prepare sodium alginate solution and metal lanthanum Salt solution, add the positive electrode material obtained in step (1) into the sodium alginate solution, stir, and then add the mixture dropwise to the metal lanthanum salt solution, after the dropwise addition, suction filter, wash, dry, and inert gas Calcination to obtain lithium nickel manganese oxide cathode material co-coated with carbon and lanthanum oxide. The positive electrode material obtained by the method of the present invention, after 200 cycles at 1C rate, has a capacity retention rate of 93% at room temperature, and a capacity retention rate of 90% at a high temperature of 55°C, which greatly improves the normal temperature and Specific capacity and cycle stability performance at high temperature.

Description

A preparation method of carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide positive electrode material

technical field

The invention relates to the technical field of modified lithium nickel manganese oxide cathode materials.

Background technique

Lithium batteries have many advantages such as high working voltage, high energy density and power density, no memory effect, long cycle life, environmental friendliness and low self-discharge rate. As one of the batteries with excellent performance in commercial secondary power sources, lithium-ion batteries are widely used in portable electronic products such as mobile phones, notebook computers, cameras, and small and medium-sized transportation equipment such as electric bicycles. At present, in lithium batteries, the cathode material not only directly participates in the electrochemical reaction as an electrode material, but also is the main provider of lithium ions in the reaction. Its performance directly affects the characteristics and indicators of the battery, and is the core and key of lithium battery technology. . As one of the current research hotspots of cathode materials, high-voltage spinel-type lithium nickel manganese oxide (LiNi _0.5 Mn _1.5 O ₄ ) has the advantages of high discharge voltage, high energy density, excellent safety, and relatively low cost. The energy density of lithium nickel manganese oxide reaches 650 Wh kg ^-1 , significantly higher than that of traditional materials such as lithium cobalt oxide (518 Wh kg ^-1 ), lithium manganese oxide (400 Whkg ^-1 ), lithium iron phosphate (495 Wh kg ^-1 ), and the preparation process of lithium nickel manganese oxide cathode material does not require atmosphere protection, and can be directly sintered and synthesized in an air atmosphere, so it is very suitable for large-scale production, and has great research value and application prospects.

However, its application in large-scale fields such as electric vehicles, hybrid electric vehicles, and smart grids has encountered difficulties due to limitations in power density and energy density. Due to the high voltage platform of 4.7V, lithium nickel manganese oxide cathode material has problems such as poor rate performance and cycle performance during charge and discharge. The main reasons are: 1. The structure of the lithium nickel manganese oxide material is destroyed during the charging and discharging process, so that the lithium ions cannot be reintercalated normally, resulting in capacity attenuation; 2. The high voltage decomposes the electrolyte, and the decomposition products will interact with the electrode materials. reaction, increasing internal resistance, hindering the deintercalation of lithium ions, depleting lithium sources, causing capacity decay, and affecting cycle life. Therefore, it is necessary to modify lithium nickel manganese oxide materials and find electrode materials with high energy and power density The key to solving this problem.

The cladding materials in the prior art are mainly single elements or compounds, including metal elements, metal oxides, phosphates or other inorganic substances.

CN109088062A discloses a preparation method of lithium nickel manganese oxide material coated with polyimide and modified by halogen element doping, wherein polyimide is used to coat and modify lithium nickel manganese oxide positive electrode material, halogen doped lithium The coating material is a single compound, and polyimide has poor conductivity, so we use a carbon material with good conductivity as the coating, and co-coat it with the metal oxide lanthanum oxide to form a dense The co-coating layer can effectively prevent the side reaction between the electrolyte and the surface of the electrode material at a high voltage of 5V, thereby improving the electrochemical performance of the material.

CN104347855A discloses a preparation method and application of phosphate-coated lithium nickel manganese oxide. First, lithium nickel manganese oxide positive electrode material is prepared, and then the positive electrode material is coated and modified with phosphate, but single phosphate modification has a negative effect on the positive electrode material The improvement of power density and energy density is not high, and the coating of phosphate increases the resistance between the material and the electrolyte, hindering the intercalation and removal of lithium ions.

CN109888208A discloses lithium ion battery cathode material and preparation method thereof, the cathode material is lithium cobaltate, lithium nickel cobalt aluminate, lithium nickel cobalt manganate, lithium manganate, lithium ferrous phosphate, lithium nickel manganate or lithium nickel cobaltate , and discloses three coating materials: lithium-titanium composite oxide, lithium-zirconium composite oxide and or lithium-phosphorus composite compound, but only one of them is selected when coating, and the modification effect is poor. Poor specific capacity and cycle stability.

Contents of the invention

The technical problem to be solved by the present invention is to provide a lithium nickel manganese oxide cathode material with excellent rate performance and cycle stability.

The advantage of the present invention is that it uses a one-step method to realize the co-coating of carbon and lanthanum oxide to modify the lithium nickel manganese oxide material, which not only improves the conductivity of the material, but also inhibits the corrosion of the electrolyte side reaction, effectively improving the The rate performance and cycle stability of the material are improved.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

The preparation method of carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide positive electrode material comprises the following steps:

(1) Weigh lithium carbonate, manganese dioxide and nickel oxide, add ethanol or water, grind and mix, dry and sinter the obtained mixture to obtain lithium nickel manganese oxide cathode material;

(2) Prepare sodium alginate solution and metal lanthanum salt solution, add the lithium nickel manganese oxide cathode material obtained in step (1) into the sodium alginate solution, stir, and then add the liquid phase mixture dropwise to the metal lanthanum salt In the solution, after the dropwise addition, the mixture is left to stand, suction filtered and washed, and the mixture is dried and calcined under an inert gas to obtain a lithium nickel manganese oxide positive electrode material coated with carbon and lanthanum oxide.

In the step (1), the molar ratio of lithium carbonate, nickel oxide and manganese dioxide=0.525:0.5:1.5, the molar ratio converted into Li:Ni:Mn is 1.05:0.5:1.5, and the lithium nickel manganate cathode material LiNi _0.5 Mn _1.5 O ₄ .

The grinding and mixing in the step (1) is ball milling, the rotating speed of the ball milling is 800 rpm, and the time is 1-3 hours.

The drying temperature in step (1) is 105±2°C.

In step (1), pre-fire at 500°C for 3~5h, and then sinter at 800°C for 7~10h.

The concentration of sodium alginate solution in step (2) is 1%~3 wt.%.

The salt solution of metal lanthanum in step (2) is a salt solution of lanthanum nitrate, lanthanum chloride, lanthanum acetate or lanthanum sulfate, and the molar ratio of metal lanthanum salt to sodium alginate is 1.2:1.

In step (2), the mass ratio of the lithium nickel manganese oxide positive electrode material to the sodium alginate solution is 1:1.

In step (2), the calcination temperature is 400° C. to 600° C., and the calcination time is 6 hours.

The drying condition in step (2) is: 100±5° C. for 4 hours.

Sodium alginate can be complexed with a variety of metal salt ions in different valence states to form microspheres, making it widely used in food, medicine, cosmetics, biotechnology and other fields. In this experiment, sodium alginate is complexed with metal lanthanum ions to form microspheres of alginate ions and metal lanthanum ions that wrap the lithium nickel manganese oxide cathode material, and then the remaining metal lanthanum ions and the displaced sodium ions are washed away with water. After drying and calcining, the modified lithium nickel manganese oxide positive electrode material co-coated by a layer of carbon and a lanthanum oxide coating layer is obtained. As we all know, a large number of oxides and fluorides (Al ₂ O ₃ , ZnO, Bi ₂ O ₃ , SnO ₂ , AlF ₃ , MgF ₂ , etc.) Electrochemical properties are of great help, but these substances are coated on the surface of lithium nickel manganese oxide, which reduces the electronic conductivity of the material surface. Since carbon materials have good electrical conductivity, we want to use the method of co-coating lanthanum oxide and carbon. The co-coating layer formed can not only effectively prevent the occurrence of side reactions, but also improve the conductivity of the material surface and reduce the The electrode impedance of the material makes the modified lithium nickel manganese oxide material have more excellent rate and cycle stability.

The beneficial effects produced by adopting the above-mentioned technical scheme are:

The advantage of the present invention is that it uses a one-step method to realize the co-coating of carbon and lanthanum oxide to modify the lithium nickel manganese oxide material, which not only improves the conductivity of the material, but also inhibits the corrosion of the electrolyte side reaction, effectively improving the The rate capability and cycle stability of the material are improved.

The method of the present invention uses two kinds of substances to co-coat the modified lithium manganese oxide positive electrode material, and the obtained modified lithium nickel manganese oxide positive electrode material, after 200 cycles at 1C rate, has a capacity retention rate of up to 93% at normal temperature, and a high temperature of 55 The capacity retention rate at ℃ is 90%, which greatly improves the specific capacity and cycle stability of the lithium nickel manganese oxide cathode material at room temperature and high temperature.

The present invention uses a carbon material with good conductivity as the coating, and co-coats it with lanthanum oxide to form a dense co-coating layer, which effectively prevents side reactions between the electrolyte and the surface of the electrode material at a high voltage of 5V. Thus improving the electrochemical performance of the material.

Description of drawings

Fig. 1 is a scanning electron microscope image of the carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide positive electrode material prepared in Example 1 of the present invention.

Figure 2 is the cycle performance curves of the carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide positive electrode material prepared in Example 1 of the present invention at 1C rate, normal temperature 25°C and high temperature 55°C.

Fig. 3 is a rate performance test curve of the carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide positive electrode material prepared in Example 1 of the present invention.

Detailed ways

Example 1

The preparation method of carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide positive electrode material comprises the following steps:

(1) Weigh 1.94g of lithium carbonate, 7.25g of manganese dioxide and 1.89g of nickel oxide in the stoichiometric ratio, put them into an 80mL ball mill jar, use 30mL of absolute ethanol as a solvent, and ball mill at 800 rpm for 2 hours to obtain The mixture was dried in an oven at 105°C, then pre-fired at 500°C for 3 hours, and then sintered at 800°C for 9 hours to obtain a pure-phase lithium nickel manganese oxide cathode material.

(2) Prepare 5 g of sodium alginate solution with a concentration of 1 wt.%, take 5 g of the pure-phase lithium nickel manganese oxide cathode material obtained in step (1) and add it to the sodium alginate solution, then add 5 mL of water to dilute, and place in a magnetic Mix well on a mixer. Then prepare 12.5 mL of lanthanum nitrate hexahydrate solution with a concentration of 1%, put the mixed solution of lithium nickel manganate and sodium alginate on the injector, and add it dropwise to the lanthanum nitrate solution at a rate of 0.1 mL/min After the dropwise addition, let stand for 10 hours, filter with suction, wash off excess lanthanum nitrate solution and replaced sodium ions with deionized water, dry at 105°C for 4h, and calcinate at 400°C for 6h under inert gas to obtain carbon and lanthanum oxide A co-coated modified lithium nickel manganese oxide cathode material.

According to the electrochemical test, the obtained carbon and lanthanum oxide co-coated lithium nickel manganese oxide positive electrode material has an initial discharge specific capacity of 136.6mAh/g at a rate of 0.2C, and after 200 cycles at a rate of 1C, the ratio The capacity is 123.6 mAh/g, and the capacity retention rate is 93%. After the material is cycled 200 times at a 1C rate at a high temperature of 55°C, the capacity retention rate remains at 90%.

Example 2

The preparation method of carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide positive electrode material comprises the following steps:

(1) Weigh 1.94g of lithium carbonate, 7.25g of manganese dioxide and 1.89g of nickel oxide in a stoichiometric ratio, put them into an 80mL ball mill jar, use 30mL of water as a solvent, and ball mill at 800 rpm for 3 hours, and the obtained mixture Dry it in an oven at 105°C, then pre-sinter at 500°C for 4 hours, and then sinter at 800°C for 10 hours to obtain a pure-phase lithium nickel manganese oxide cathode material.

(2) Prepare 5g of sodium alginate solution with a concentration of 2 wt.%, take 5g of the pure-phase lithium nickel manganese oxide cathode material obtained in step (1) and add it to the sodium alginate solution, then add 5mL of water to dilute, and place in a magnetic Mix well on a mixer. Then prepare 25 mL of lanthanum nitrate hexahydrate solution with a concentration of 1%, put the mixed solution of lithium nickel manganate and sodium alginate on the injector, and add it dropwise to the lanthanum nitrate solution at a rate of 0.1 mL/min. After the dropwise addition, let stand for 10 hours, filter with suction, wash off excess lanthanum nitrate solution and replaced sodium ions with deionized water, dry at 100°C for 4h, and calcinate at 500°C for 6h under inert gas to obtain carbon and lanthanum oxide co- Coated modified lithium nickel manganese oxide cathode material.

According to electrochemical tests, the obtained carbon and lanthanum oxide co-coated lithium nickel manganese oxide positive electrode material has a specific discharge capacity of 134.5mAh/g for the first time at a rate of 0.2C, and after 200 cycles at a rate of 1C, the specific capacity is The capacity is 122.1mAh/g, and the capacity retention rate is 92%. After the material is cycled 200 times at 1C rate at a high temperature of 55°C, the capacity retention rate is 89.1%.

Example 3

The preparation method of carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide positive electrode material comprises the following steps:

(1) Weigh 1.94g of lithium carbonate, 7.25g of manganese dioxide and 1.89g of nickel oxide in the stoichiometric ratio, put them into an 80mL ball mill jar, use 30mL of absolute ethanol as a solvent, and ball mill at 800 rpm for 2 hours to obtain The mixture was dried in an oven at 103°C, then pre-fired at 500°C for 5 hours, and then sintered at 800°C for 7 hours to obtain a pure-phase lithium nickel manganese oxide cathode material.

(2) Prepare 5 g of sodium alginate solution with a concentration of 3 wt.%, take 5 g of the pure-phase lithium nickel manganese oxide cathode material obtained in step (1) and add it to the sodium alginate solution, then add 5 mL of water to dilute, and place in a magnetic Mix well on a mixer. Then prepare 40 mL of lanthanum nitrate solution with a concentration of 1%, put the mixed solution of lithium nickel manganate and sodium alginate on the injector, and add it dropwise to the lanthanum nitrate hexahydrate solution at a rate of 0.1 mL/min. After the dropwise addition, let stand for 10 hours, filter with suction, wash off excess lanthanum nitrate solution and replaced sodium ions with deionized water, dry at 105°C for 4h, and calcinate at 600°C for 6h under inert gas to obtain carbon and lanthanum oxide co- Coated modified lithium nickel manganese oxide cathode material.

According to the electrochemical test, the obtained carbon and lanthanum oxide co-coated lithium nickel manganese oxide positive electrode material has an initial discharge specific capacity of 132.0mAh/g at a rate of 0.2C, and after 200 cycles at a rate of 1C, the ratio The capacity is 120 mAh/g, and the capacity retention rate is 90.5%. After the material is cycled 200 times at 1C rate at a high temperature of 55 °C, the capacity retention rate is 88%.

Example 4

The preparation method of carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide positive electrode material comprises the following steps:

(1) Weigh 1.94g of lithium carbonate, 7.25g of manganese dioxide and 1.89g of nickel oxide in the stoichiometric ratio, put them into an 80mL ball mill jar, use 30mL of absolute ethanol as a solvent, and ball mill at 800 rpm for 2 hours to obtain The mixture was dried in an oven at 105°C, then pre-fired at 500°C for 3 hours, and then sintered at 800°C for 9 hours to obtain a pure-phase lithium nickel manganese oxide cathode material.

(2) Prepare 5 g of sodium alginate solution with a concentration of 1 wt.%, take 5 g of the pure-phase lithium nickel manganese oxide cathode material obtained in step (1) and add it to the sodium alginate solution, then add 5 mL of water to dilute, and place in a magnetic Mix well on a mixer. Subsequently, 7 mL of lanthanum chloride solution with a concentration of 1 wt.% was prepared, and the mixed solution of lithium nickel manganese oxide and sodium alginate was added dropwise to lanthanum chloride at a rate of 0.1 mL/min on the injector. In the solution, after the dropwise addition, stand still for 10 hours, filter with suction, wash off excess lanthanum chloride solution with deionized water, dry at 105°C for 4h, and calcinate at 400°C for 6h under inert gas to obtain carbon and lanthanum oxide co-coated Modified lithium nickel manganese oxide cathode material.

According to the electrochemical test, the obtained carbon and lanthanum oxide co-coated lithium nickel manganese oxide positive electrode material has an initial discharge specific capacity of 135.3mAh/g at a rate of 0.2C, and after 200 cycles at a rate of 1C, the ratio The capacity is 122.0 mAh/g, and the capacity retention rate is 92.8%. After the sample is cycled 200 times at 1C rate at a high temperature of 55°C, the capacity retention rate is 89%.

Example 5

The preparation method of carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide positive electrode material comprises the following steps:

(1) Weigh 1.94g of lithium carbonate, 7.25g of manganese dioxide and 1.89g of nickel oxide in the stoichiometric ratio, put them into an 80mL ball mill jar, use 30mL of absolute ethanol as a solvent, and ball mill at 800 rpm for 2 hours to obtain The mixture was dried in an oven at 105°C, then pre-fired at 500°C for 3 hours, and then sintered at 800°C for 9 hours to obtain a pure-phase lithium nickel manganese oxide cathode material.

(2) Prepare 5g of sodium alginate solution with a concentration of 2 wt.%, take 5g of the pure-phase lithium nickel manganese oxide cathode material obtained in step (1) and add it to the sodium alginate solution, then add 5mL of water to dilute, and place in a magnetic Mix well on a mixer. Subsequently, 18 mL of lanthanum acetate solution with a concentration of 1 wt.% was prepared, and the mixed solution of lithium nickel manganese oxide and sodium alginate was added dropwise to the lanthanum acetate solution at a rate of 0.1 mL/min on the injector. After the dropwise addition, let stand for 10 hours, filter with suction, wash off excess lanthanum acetate solution and displaced sodium ions with deionized water, dry at 105°C for 4 hours, and calcinate at 500°C for 6 hours under inert gas to obtain carbon and lanthanum oxide co- Coated modified lithium nickel manganese oxide cathode material.

According to the electrochemical test, the obtained carbon and lanthanum oxide co-coated lithium nickel manganese oxide positive electrode material has a specific discharge capacity of 134.9mAh/g for the first time at a rate of 0.2C, and after 200 cycles at a rate of 1C, the ratio The capacity is 121.6 mAh/g, and the capacity retention rate is 92.1%. After the sample is cycled 200 times at 1C rate at a high temperature of 55°C, the capacity retention rate is 90.5%.

Claims (10)

1. The preparation method of carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide positive electrode material is characterized in that: comprising the following steps: (1) Weigh lithium carbonate, manganese dioxide and nickel oxide, add ethanol or water, grind and mix, dry and sinter the obtained mixture to obtain lithium nickel manganese oxide cathode material; (2) Prepare sodium alginate solution and metal lanthanum salt solution, add the lithium nickel manganate cathode material obtained in step (1) into the sodium alginate solution, stir, and then add the liquid phase mixture dropwise to the metal lanthanum salt solution After the dropwise addition, the mixture was left standing, suction filtered, washed, dried, and calcined under an inert gas to obtain a lithium nickel manganese oxide cathode material co-coated with carbon and lanthanum oxide. 2. the preparation method of carbon and lanthanum oxide co-coating modified lithium nickel manganese oxide cathode material according to claim 1, is characterized in that: the mole of lithium carbonate, nickel oxide and manganese dioxide in the described step (1) Ratio=0.525:0.5:1.5, LiNi _0.5 Mn _1.5 O ₄ is obtained as a lithium nickel manganese oxide positive electrode material. 3. the preparation method of carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide cathode material according to claim 1, is characterized in that: in described step (1), grinding and mixing is ball milling and mixing, and the ball milling speed is 800 rpm /min, the time is 1~3h. 4 . The method for preparing the modified lithium nickel manganese oxide positive electrode material co-coated with carbon and lanthanum oxide according to claim 1 , wherein the drying temperature in step (1) is 105±2° C. 5. The preparation method of carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide positive electrode material according to claim 1, characterized in that: in the step (1), pre-fire at 500°C for 3~5h, and then at 800°C Sintering at ℃ for 7~10h. 6. The preparation method of carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide cathode material according to claim 1, characterized in that: the concentration of sodium alginate solution in the step (2) is 1 ~ 3 wt .%. 7. The preparation method of carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide cathode material according to claim 6, characterized in that: the metal lanthanum salt solution in the step (2) is lanthanum nitrate, lanthanum chloride , a solution of lanthanum acetate or lanthanum sulfate, the molar ratio of metal lanthanum salt to sodium alginate is 1.2:1. 8. The preparation method of carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide positive electrode material according to claim 1, characterized in that: lithium nickel manganese oxide positive electrode material and sodium alginate solution in the step (2) The mass ratio is 1:1. 9. The preparation method of carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide positive electrode material according to claim 1, characterized in that: the calcination temperature in the step (2) is 400 ° C ~ 600 ° C, and the calcination The time is 6h. 10. The preparation method of carbon and lanthanum oxide co-coated modified lithium nickel manganese oxide positive electrode material according to claim 1, characterized in that: the drying condition in the step (2) is: 100±5°C for 4 hours.