CN102386381B - A kind of preparation method of lithium-ion battery nanoscale cathode material - Google Patents

Abstract

The invention belongs to the field of nanometer material preparation technology and green energy, and relates to a method for preparing a nanoscale cathode material LiNi _1/3 Mn _1/3 Co _1/3 O ₂ applied to a lithium ion battery. The method mainly solves the disadvantages of high calcination temperature, long calcination time and non-uniform product particle size required by the current synthetic materials. Add a certain amount of templating agent to the mixed aqueous solution of nickel salt, manganese salt, and cobalt salt, and then add a precipitating agent and a complexing agent dropwise to form a precipitate; react the above precipitate with the mixed solution in a hydrothermal kettle under high pressure, wash and dry Obtain nickel manganese cobalt oxide; then mix with lithium salt evenly, calcined, and cooled to obtain the final product. The invention can obtain a product with good electrochemical performance in a short calcining time, saves energy consumption, and has obvious economic benefits in large-scale application of industrial synthesis.

Description

A kind of preparation method of lithium-ion battery nanoscale cathode material

technical field

The invention belongs to the field of nanometer material preparation technology and green energy, and relates to a method for preparing a nanoscale cathode material LiNi _1/3 Mn _1/3 Co _1/3 O ₂ applied to a lithium ion battery.

Background technique

The two major tasks of lithium-ion battery research are to improve performance (mainly high energy density and power density, long life, safety) and reduce cost. The cathode material is the key to improving the performance of lithium-ion batteries, which determines the main performance indicators of lithium-ion batteries. As far as the positive electrode material in power lithium-ion secondary batteries is concerned, lithium cobalt oxide (LiCoO ₂ ) has the problems of thermal runaway risk and high cost of large batteries; lithium manganese oxide (LiMn ₂ O ₄ ) has low cost, environmental friendliness, and safety Higher advantages, but its low energy density, poor cycle performance, and prominent Mn dissolution problems; lithium iron phosphate (LiFePO ₄ ) system has the advantages of low cost, high charging stability and safety, but low energy density, poor electronic conductivity, preparation Process complexity and other issues. In recent years, the new layered lithium intercalation ternary system Li-Ni-Mn-Co-O composite oxide has developed rapidly, and its representative is lithium nickel manganese cobaltate (LiNi _1/3 Mn _1/3 Co _{1/ 3} O ₂ ). This kind of material has stable electrochemical performance, high discharge capacity and discharge rate, good thermal stability, and good safety. Its comprehensive performance is better than any single-component compound. It is a new type of positive electrode material that is expected to replace lithium cobalt oxide.

Although LiNi _1/3 Mn _1/3 Co _1/3 O ₂ material has broad development prospects, its preparation process is complex and unsuitable for industrial production, which limits its practical application. The commonly used solid-phase synthesis method has simple operation steps, but the energy consumption is large, the reaction time is long, and the heterogeneity of the synthesized material components is not enough; although liquid-phase methods such as sol-gel method and precipitation method can synthesize components with uniform However, the calcination temperature of heat treatment is very high (over 900 ℃), and the calcination time is long, which makes the energy consumption of the preparation material large. At the same time, the low electrical conductivity of the cathode material seriously affects its electrochemical performance under high current. Nanoscale powder particles are an effective way to improve the high-current electrochemical performance of positive electrode materials: they can shorten the diffusion path of lithium ions, increase the specific surface area of the material, and increase the contact area between the active material and the electrolyte, thereby improving the ion conductivity. .

Kobayashi et al. (Kobayashi H, Arachi Y, Emura S, et al. Investigation on lithium de-intercalation mechanism for Li1-yNi1/3Mn1/3Co1/3O2[J]. Journal of Power Sources, 2005, 146: 640-644. ) was calcined at 1000°C for 24 hours by hydroxide precipitation method to obtain LiNi _1/3 Mn _1/3 Co _1/3 O ₂ with a discharge capacity of 160 mAh/g. However, the present invention can obtain a product with good electrochemical performance within a short calcination time (2-12 hours), which is cheap and easy to industrialize; water is used as a solvent, which is green and environmentally friendly; the addition of templates makes the product regular in shape and size It is uniform, not easy to agglomerate, and has excellent high-rate charge and discharge performance. Compared with the methods reported in other literature and patents, it has outstanding innovation and advancement.

Contents of the invention

The object of the present invention is to provide a method capable of preparing LiNi _1/3 Mn _1/3 Co _1/3 O ₂ anode material of nanoscale lithium ion battery with good electrochemical performance within a short calcination time.

The preparation method of the nanoscale cathode material LiNi _1/3 Mn _1/3 Co _{1/3 O} of the present invention, its specific steps are as follows:

(1) Using soluble nickel salt, manganese salt, and cobalt salt as raw materials, according to the ratio of nickel, manganese, and cobalt in the positive electrode material LiNi _1/3 Mn _1/3 Co _1/3 O ₂ components, the nickel salt, manganese salt, and manganese salt are prepared Salt, cobalt salt mixed aqueous solution, wherein the metal content is 2 mol/L;

(2) Add a certain amount of template agent to the solution in step (1), the ratio of template agent mass to target product mass is 0.1~3, and stir at 800~1200 rpm for 0.2~1.5 hours;

(3) Add the precipitant and complexing agent dropwise to the solution in step (2) under _N2 atmosphere, and stir at 800~1200 rpm at the same time, keep the reaction temperature at 40~70 ℃, and keep the pH value of the reaction system 9~13. After the precipitation is formed, continue to stir for 1 to 3 hours;

(4) Transfer the precipitate and solution formed in step (3) to a hydrothermal kettle with a filling degree of 60-90%, and conduct a high-pressure thermal reaction in a hydrothermal environment of 100-280 °C for 6-40 hours;

(5) Filter and clean the precipitate in step (4), and dry the filter cake to obtain the precursor nickel manganese cobalt oxide; mix the precursor and lithium compound in a mixer according to the proportion of positive electrode material components; Preheat at 400°C for 2-12 hours, heat up to 600-1000°C for 2-15 hours, and then cool and grind to obtain LiNi _1/3 Mn _1/3 Co _1/3 O ₂ with nanoscale layered structure.

The nickel salt used is nickel acetate, nickel nitrate or nickel oxalate.

The manganese salt used is manganese acetate, manganese nitrate or manganese oxalate.

The cobalt salt used is cobalt acetate, cobalt nitrate or cobalt oxalate.

The lithium salt used is lithium acetate, lithium nitrate, lithium oxalate, lithium formate, lithium nitrite or lithium citrate.

The templates used are activated carbon powder, activated carbon fiber, carbon nanotubes, sawdust, wood powder, bamboo carbon powder, corn stalk, cellulose, peanut shell, carbon aerogel, starch, sucrose, ethyl phosphate, polypropylene glycol, Polyacrylamide, polypropylene ether, polystyrene, polyvinyl ether, polycarbonate or polymethyl methacrylate.

The complexing agent used is urea or ammonia water.

The precipitating agent used is lithium hydroxide or sodium hydroxide, and its total molar ratio to nickel ion + manganese ion + cobalt ion is 2-4. The molar ratio of complexing agent to precipitating agent is 0.1~2.

The preparation method of the nanoscale cathode material LiNi _1/3 Mn _1/3 Co _1/3 O ₂ of the present invention is characterized in that the average grain size of 15 nm to 200 nm can be prepared by changing the template agent and adjusting the calcination time and temperature. The nanoscale LiNi _1/3 Mn _1/3 Co _1/3 O ₂ composite oxide has a tap density of 1.8~2.8 g/m ³ . Under the condition of 0.2 C charge and discharge, its discharge capacity is above 178 mAh/g.

The advantages of the present invention are:

1. Short heat treatment time and low energy consumption;

2. The process is simple and easy for industrial scale-up. The prepared ternary system LiNi _1/3 Mn _1/3 Co _1/3 O ₂ has uniform particle size distribution, regular shape, is not easy to agglomerate, and is easy to control the composition;

3. Water is used as a solvent in the precursor synthesis process, which is green and environmentally friendly;

4. The prepared ternary system LiNi _1/3 Mn _1/3 Co _1/3 O ₂ has outstanding charge and discharge performance. Under 0.2 C charge and discharge conditions, its reversible lithium intercalation capacity is above 178 mAh/g, and 1.0 C charge The capacity retention rate of 40 cycles under discharge conditions is about 98%, and the cycle performance is good, so it is an ideal positive electrode material for power lithium ion secondary batteries.

Description of drawings

Fig. 1 is the scanning electron micrograph of the ternary system LiNi _1/3 Mn _1/3 Co _1/3 O ₂ composite materials prepared in embodiment 1, and the magnification is 20,000 times;

Figure 2 is the initial charge-discharge curve of the ternary system LiNi _1/3 Mn _1/3 Co _1/3 O ₂ prepared in Example 2, the voltage range is 2.8-4.5 V, and the electrolyte is 1mol/L LiPF ₆ /EC -DMC (1:1), the charge and discharge current density is 0.2 C;

Figure 3 is the cycle performance curve of the ternary system LiNi _1/3 Mn _1/3 Co _1/3 O ₂ prepared in Example 1, the voltage range is 2.8-4.5V, and the electrolyte is 1mol/L LiPF ₆ /EC- DMC (1:1), the charge and discharge current density is 1.0 C.

Detailed ways

Embodiment 1: Get 11.63 g nickel nitrate, 7.158 g manganese nitrate and 11.64 g cobalt nitrate, dissolve in deionized aqueous solution, the concentration of metal ion is 2 mol/L, add 0.5 g polypropylene glycol simultaneously, stir 0.5 with 800 rpm Hour. Under _N2 atmosphere, 0.08 mol aqueous solution containing lithium hydroxide and 0.08 mol urea aqueous solution were simultaneously added dropwise to the above solution, and stirred at 800 rpm, the reaction temperature was kept at 45 °C, and the pH value of the reaction system was kept at 10. Stirring was continued for 2 hours after the precipitate formed. The formed precipitate and solution were transferred to a hydrothermal kettle with a filling degree of 70%. After reacting in a hydrothermal environment at 160 °C for 12 hours, the precipitate was taken out, filtered and cleaned, and the filter cake was dried to obtain the precursor nickel manganese cobalt oxide. The precursor was mixed with 2.76 g lithium nitrate in a mixer, preheated at 400 °C for 4 hours, heated to 800 °C for 4 hours, cooled and ground to obtain LiNi _1/3 Mn _{1/ 3} Co _1/3 O ₂ . Its average grain size is 100 nm, and its discharge capacity is 178.7 mAh/g under 0.2 C charge-discharge condition, and the capacity retention rate after 40 cycles of 1.0 C charge-discharge condition is 97.9%.

Embodiment 2: Get 9.95 g nickel acetate, 9.80 g manganese acetate and 9.96 g cobalt acetate and dissolve in deionized aqueous solution, the concentration of metal ion is 2 mol/L, add 1.5 g carbon nanotubes simultaneously, stir 0.6 with 1000 rpm Hour. Under _N2 atmosphere, 0.12 mol aqueous solution containing sodium hydroxide and 0.05 mol urea aqueous solution were added dropwise to the above solution at the same time, and stirred at 1200 rpm, the reaction temperature was kept at 40 °C, and the pH value of the reaction system was kept at 11. Stirring was continued for 2 hours after the precipitate formed. The formed precipitate and solution were transferred to a hydrothermal kettle with a filling degree of 70%. After reacting in a hydrothermal environment at 150 °C for 16 hours, the precipitate was taken out, filtered and cleaned, and the filter cake was dried to obtain the precursor nickel manganese cobalt oxide. Mix the precursor with 4.08 g lithium acetate in a mixer; preheat treatment at 350 °C for 3.5 hours, heat up to 850 °C for 6 hours, cool and grind to obtain LiNi _1/3 Mn ₁ with nanoscale layered structure _/3 Co _1/3 O ₂ . Its average grain size is 120 nm. Under 0.2 C charge and discharge conditions, its discharge capacity is 187.7 mAh/g, and the capacity retention rate after 1.0 C charge and discharge conditions for 40 cycles is 98.7 %.

Example 3: Dissolve 17.06g of nickel oxalate, 19.06g of manganese oxalate, and 19.59g of cobalt oxalate in a deionized aqueous solution. The concentration of metal ions is 2 mol/L. At the same time, 0.7 g of corn stalks are added and stirred at 1000 rpm for 1 hour . Under _N2 atmosphere, 0.16 mol aqueous solution containing lithium hydroxide and 0.05 mol urea aqueous solution were added dropwise to the above solution at the same time, and stirred at 1100 rpm, the reaction temperature was kept at 45 °C, and the pH value of the reaction system was kept at 12. Stirring was continued for 2 hours after the precipitate formed. The formed precipitate and solution were transferred to a hydrothermal kettle with a filling degree of 85%. After reacting in a hydrothermal environment at 200 °C for 12 hours, the precipitate was taken out, filtered and cleaned, and the filter cake was dried to obtain the precursor nickel manganese cobalt oxide. The precursor was mixed with 4.08 g lithium oxalate in a mixer; preheated at 450 °C for 4 hours, heated to 900 °C for 5 hours, cooled and ground to obtain LiNi _1/3 Mn ₁ with nanoscale layered structure _/3 Co _1/3 O ₂ . Its average grain size is 150 nm. Under the condition of 0.2 C charge and discharge, the discharge capacity is 192.3 mAh/g, and the capacity retention rate after 40 cycles of 1.0 C charge and discharge is 99.2%.

Embodiment 4: get 11.63 g nickel nitrate, 7.158 g manganese nitrate and 11.64 g cobalt nitrate to be dissolved in deionized aqueous solution, the concentration of metal ion is 2 mol/L, add 1.0 g bamboo charcoal powder simultaneously, stir 0.5 hour with 1000 rpm . Under _N2 atmosphere, 0.2 mol aqueous solution containing lithium hydroxide and 0.04 mol urea aqueous solution were added dropwise to the above solution at the same time, and stirred at 1000 rpm, the reaction temperature was kept at 40 °C, and the pH value of the reaction system was kept at 13. Stirring was continued for 1 hour after the precipitate formed. The formed precipitate and solution were transferred to a hydrothermal kettle with a filling degree of 85%. After reacting in a hydrothermal environment at 180 °C for 20 hours, the precipitate was taken out, filtered and cleaned, and the filter cake was dried to obtain the precursor nickel manganese cobalt oxide. Mix the precursor with 11.28 g of lithium citrate in a mixer; preheat at 400 °C for 4 hours, heat up to 800 °C for 7 hours, cool and grind to obtain LiNi _1/3 Mn with nanoscale layered structure _1/3 Co _1/3 O ₂ . Its average grain size is 130 nm. Under the condition of 0.2 C charge and discharge, the discharge capacity is 200.3 mAh/g, and the capacity retention rate of 40 cycles under the condition of 1.0 C charge and discharge is 99.5%.

Claims (2)

1. a lithium-ion battery nanoscale cathode material LiNi _1/3 Mn _1/3 Co _1/3 O ₂ preparation method, it is characterized in that comprising the following steps: (1) Using soluble nickel salt, manganese salt, and cobalt salt as raw materials, according to the ratio of nickel, manganese, and cobalt in the positive electrode material LiNi _1/3 Mn _1/3 Co _1/3 O ₂ components, the nickel salt, manganese salt, and manganese salt are prepared A mixed solution of salt and cobalt salt, in which the metal content is 2 mol/L; (2) Add a certain amount of templating agent to the solution in step (1), the ratio of the mass of the templating agent to the mass of the target product is 0.1 to 3, and stir at 800 to 1200 rpm for 0.2 to 1.5 hours. The template is Activated carbon powder, activated carbon fiber, carbon nanotubes, sawdust, wood powder, bamboo carbon powder, corn stalks, cellulose, peanut shells, carbon airgel, starch, sucrose, ethyl phosphate, polypropylene glycol, polyacrylamide, poly Propylene ether, polystyrene, polyvinyl ether, polycarbonate or polymethyl methacrylate; (3) Add the precipitant and complexing agent dropwise to the solution in step (2) under _N2 atmosphere, and stir at 800~1200 rpm at the same time, keep the reaction temperature at 40~70 ℃, and keep the pH value of the reaction system 9~13, keep stirring for 1~3 hours after the precipitation is formed; (4) Transfer the precipitate and solution formed in step (3) to a hydrothermal kettle with a filling degree of 60-90%, and conduct a high-pressure thermal reaction in a hydrothermal environment of 100-280 °C for 6-40 hours; (5) Filter and clean the precipitate in step (4), and dry the filter cake to obtain the precursor nickel manganese cobalt oxide; mix the precursor and lithium salt in a mixer according to the proportion of positive electrode material components; Preheat at 400°C for 2-12 hours, heat up to 600-1000°C for 2-15 hours, and then cool and grind to obtain LiNi _1/3 Mn _1/3 Co _1/3 O ₂ with nanoscale layered structure. 2. preparation method as claimed in claim 1 is characterized in that, used nickel salt is nickel acetate, nickel nitrate or nickel oxalate. 3. preparation method as claimed in claim 1, is characterized in that, used manganese salt is manganese acetate, manganese nitrate or manganese oxalate. 4. preparation method as claimed in claim 1, is characterized in that, used cobalt salt is cobalt acetate, cobalt nitrate or cobalt oxalate. 5. preparation method as claimed in claim 1, is characterized in that, lithium salt used is lithium acetate, lithium nitrate, lithium oxalate, lithium formate, lithium nitrite or lithium citrate. 6. preparation method as claimed in claim 1, is characterized in that, complexing agent used is urea or ammoniacal liquor. 7. preparation method as claimed in claim 1, is characterized in that, used precipitation agent is lithium hydroxide or sodium hydroxide, and it is 2～4 with nickel ion+manganese ion+cobalt ion total molar ratio, complexing agent and The molar ratio of the precipitating agent is 0.1~2.

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