CN102009998A - Method for preparing lithium ion battery cathode material lithium titanate - Google Patents

Abstract

The invention relates to a preparation method of lithium titanate, a negative electrode material of a lithium ion battery. The method comprises the following steps: uniformly mixing the lithium source, TiO ₂ and carbonizing agent, the material ratio is molar ratio Li:Ti=0.80～0.88:1, mass ratio TiO ₂ : carbonizing agent=4～8:1, and then Add the mixture into a polyacrylamide (PAM) aqueous solution with a concentration of 0.15% to 0.2%, the mass ratio of which is polyacrylamide: TiO ₂ =0.002 to 0.003:1, then stir vigorously, and after mixing evenly, put the material in In the muffle furnace, first keep the temperature at 100°C for 3 hours, then pre-fire at 600°C, keep the temperature for 12 hours, cool to room temperature with the furnace, grind it into powder, and then calcinate in the muffle furnace at 750-950°C for 16 hours to obtain the product. The Li ₄ Ti ₅ O ₁₂ material obtained by the invention has an initial discharge capacity of 170mAh/g, and after 20 cycles, the capacity has almost no attenuation, the polarization is reduced, and the electrochemical performance is excellent.

Description

A kind of preparation method of lithium titanate lithium ion battery negative electrode material

technical field

The invention relates to the technical field of battery material preparation, in particular to a preparation method of lithium titanate, a negative electrode material of a lithium ion battery.

Background technique

Lithium-ion battery is a new type of rechargeable battery. It has high volume specific energy and mass specific energy, is rechargeable and pollution-free, and has three advantages in the current battery industry development. It is called "the most promising chemical battery". Power", so once it came out, it has received widespread attention and developed very rapidly. In recent years, it has been widely used in various portable electronic products and communication tools, and has been gradually developed as a power source for electric vehicles. It is a safe and environmentally friendly new energy source.

The successful commercialization of lithium-ion batteries is mainly attributed to the replacement of metallic lithium anodes by lithium intercalation compounds. Research and development of new anode materials with better electrochemical performance is a hot topic in the field of lithium-ion battery research. At present, lithium-ion battery anode materials mostly use lithium-intercalated carbon materials. The advantages of graphite materials are wide sources, cheap price, low charge and discharge voltage platform, and high reversible capacity (theoretical value 372mAhg). However, graphite has poor compatibility with solvents, and the high-current charge-discharge performance is not good. During the first charge-discharge, the graphite layer is peeled off due to the co-embedding of solvent molecules, resulting in a decrease in the cycle life of the electrode. In order to solve the various defects of existing materials, a lot of research has been done in the battery industry. While making various improvements to carbon anode materials to improve their performance, the development of new anode materials has always been the focus of attention. Therefore, looking for ideal negative electrode active materials for lithium-ion batteries from the aspects of resources, environmental protection and safety performance will still be a research hotspot in the world's chemical power industry for some time to come.

In 1996, Canadian researcher K.zaghib proposed for the first time that lithium titanate materials could be used as negative electrodes and high-voltage positive electrodes to form lithium-ion batteries, and carbon electrodes to form electrochemical hybrid capacitors. Later, Koshiba Shinharu and others also carried out research on it as a lithium ion anode material. In 2001, GGAmatucci et al. used Li ₄ Ti ₅ O ₁₂ to replace the negative electrode of the electric double layer capacitor, and used the electrolyte for lithium batteries to obtain an energy density of 20wh/kg. Since then, people have started a lot of research on Li ₄ Ti ₅ O ₁₂ as anode material. Japan's Toshiba Corporation announced in 2007 the development of a lithium-ion battery "SCiB" based on Li ₄ Ti ₅ O ₁₂ , which is intended for use in the hybrid power field. Enerdel Corporation of the United States also demonstrated Li ₄ Ti ₅ O ₁₂ lithium-ion batteries for hybrid vehicles at the AABC-07 meeting.

Li ₄ Ti ₅ O ₁₂ has many advantages as an anode material for lithium-ion batteries: (1) Li ₄ Ti ₅ O ₁₂ has a high theoretical specific capacity of 175mAh/g; (2) its skeleton structure is almost unchanged during charging and discharging , has the characteristics of "zero strain", so the cycle performance is stable; (3) the lithium intercalation potential is high (1.55vs.Li/Li ⁺ ), and it is not easy to cause metal lithium precipitation, eliminating potential safety hazards; (4) Li ₄ Ti ₅ O ₁₂ Among them, the lithium ion diffusion coefficient (2×10 ^-8 cm ² /s) is about 10 times that of graphite, which has the advantage of high current charge and discharge. At the same time, titanium resources are abundant and the price is low. Therefore, Li ₄ Ti ₅ O ₁₂ is an ideal negative electrode candidate material for lithium-ion batteries.

At present, there are many methods for preparing lithium titanate materials, and the most widely used method is the high-temperature solid-phase method, which is easy to operate and easy to realize industrial production. However, there are two commonly used solid-phase methods. One is to directly mix the raw materials and calcine them. The material particles obtained in this way are relatively large, and the particle size distribution is not uniform, and the electrochemical performance is unstable; the other is to obtain small particles. For particles with smaller diameters, mechanical ball milling, sieving, etc. are often used to pretreat the raw materials, which complicates the synthesis process and increases the production cost.

Invention content:

The present invention aims at the shortcomings of the high-temperature solid-phase method, by using low-cost titanium dioxide as the titanium source, by mixing lithium salt, titanium dioxide, and carbonization agent at one time, complicated feeding methods are avoided, and an appropriate amount of solvent is added to the precursor. The materials are vigorously stirred evenly to realize the mixing and wrapping of the materials at the molecular level, and the Li ₄ Ti ₅ O ₁₂ negative electrode material with excellent electrochemical performance is prepared through two-step calcination. The cost of the synthesis process is reduced, making it easy to realize industrialization.

Technical scheme of the present invention is:

A preparation method of lithium titanate lithium ion battery negative electrode material, comprising the following steps:

Lithium source, TiO ₂ and carbonizing agent are mixed evenly, and its material ratio is molar ratio Li: Ti=0.80～0.88:1, mass ratio TiO ₂ : Carbonizing agent=4～8:1, then the mixture is added to a concentration of In the 0.15%～0.2% polyacrylamide (PAM) aqueous solution, the mass ratio is polyacrylamide:TiO ₂ =0.002～0.003:1, then vigorously stir, after mixing evenly, put the material in the muffle furnace for 100 ℃ for 3 hours, then pre-fired at 600 ℃ for 12 hours, cooled to room temperature with the furnace, ground into powder, and then calcined in a muffle furnace at 750-950 ℃ for 16 hours to obtain the product.

In the preparation method, in addition to the lithium source, TiO ₂ and carbonization agent, Na ₂ CO ₃ is also added to the raw materials, wherein the molar ratio Na:Ti=0.01～0.10:5;

In the described preparation method, in addition to lithium source, TiO ₂ and carbonization agent, manganese acetate is also added in the raw material, wherein the molar ratio Mn:Li=0.01～0.12:4;

Described lithium source is lithium carbonate or lithium hydroxide;

The carbonization agent is activated carbon, citric acid or glucose.

The beneficial effects of the present invention are: the present invention prevents the crystal nuclei of Li ₄ Ti ₅ O ₁₂ from growing too large microscopically by adding a certain amount of carbon source as the carbonization agent, and produces CO ₂ gas to be discharged during the calcination process, inhibiting agglomeration of particles. Using PAM aqueous solution as a solvent, the raw materials are mixed in the solution environment, and the contact between the raw material particles is more sufficient and more uniform. The obtained Li ₄ Ti ₅ O ₁₂ material has an initial discharge capacity of 170mAh/g, which is ^close to the theoretical capacity. The particle size is small and evenly distributed. The material has excellent cycle performance. After 20 cycles, the capacity has almost no attenuation, the polarization is reduced, and the electrochemical performance is excellent.

The following describes in detail with reference to the embodiments and the accompanying drawings.

Description of drawings

Accompanying drawing 1 is the X-ray diffraction pattern of the product that embodiment 2, embodiment 5 and embodiment 6 prepare;

Accompanying drawing 2 is the SEM figure of the product prepared under the different temperatures of embodiment 1,2,3,4;

Accompanying drawing 3 is the initial charge-discharge specific capacity curve at 0.1C of the product prepared in embodiment 2, embodiment 5 and embodiment 6;

Accompanying drawing 4 is the SEM figure of the lithium position doped Na product Li _3.97 Na _0.03 Ti ₅ O ₁₂ prepared in embodiment 5;

Accompanying drawing 5 is the SEM figure of the titanium position doped Mn product Li ₄ Ti _4.96 Mn _0.04 O ₁₂ prepared in embodiment 6;

Accompanying drawing 6 is the first charge-discharge specific capacity curve at 0.1C of the product prepared in embodiment 2, embodiment 5 and embodiment 6;

Accompanying drawing 7 is the cycle performance curve of the product prepared in embodiment 2, embodiment 5 and embodiment 6 at 0.2C;

Accompanying drawing 8 is the initial charge-discharge specific capacity curve of the product prepared in Example 7 at 0.1C.

Detailed ways

Example 1

Weigh 1.5517g (0.021mol) Li ₂ CO ₃ , 3.9935g (0.05mol) TiO ₂ , and 1.0g citric acid, shake and mix them evenly in a small plastic bottle. Weigh 0.01 g of polyacrylamide and place it in a crucible, add 5 ml of double-distilled water, and wait for it to fully dissolve to form an aqueous solution of polyacrylamide. Add the mixture of the above three into the polyacrylamide aqueous solution, and stir vigorously to form a paste-like rheological phase. In the muffle furnace, first keep the temperature at 100°C for 3h, then pre-fire at 600°C, hold the temperature for 12h, cool down to room temperature with the furnace, grind it into powder, and then calcinate at 800°C for 16h in the muffle furnace to obtain pure phase Li ₄ Ti ₅ O ₁₂ products.

Example 2

Weigh 1.5517g (0.021mol) Li ₂ CO ₃ , 3.9935g (0.05mol) TiO ₂ , and 1.0g citric acid, shake and mix them evenly in a small plastic bottle. Weigh 0.01 g of polyacrylamide and place it in a crucible, add 5 ml of double-distilled water, and wait for it to fully dissolve to form an aqueous solution of polyacrylamide. Add the mixture of the above three into the polyacrylamide aqueous solution, and stir vigorously to form a paste-like rheological phase. In the muffle furnace, first keep the temperature at 100°C for 3h, then pre-fire at 600°C, hold the temperature for 12h, cool down to room temperature with the furnace, grind it into powder, and then calcinate in the muffle furnace at 850°C for 16h to obtain pure phase Li ₄ Ti ₅ O ₁₂ products.

Example 3

Weigh 1.5517g (0.021mol) Li ₂ CO ₃ , 3.9935g (0.05mol) TiO ₂ , and 1.0g citric acid, shake and mix them evenly in a small plastic bottle. Weigh 0.01 g of polyacrylamide and place it in a crucible, add 5 ml of double-distilled water, and wait for it to fully dissolve to form an aqueous solution of polyacrylamide. Add the mixture of the above three into the polyacrylamide aqueous solution, and stir vigorously to form a paste-like rheological phase. In the muffle furnace, first keep the temperature at 100°C for 3h, then pre-fire at 600°C, hold the temperature for 12h, cool down to room temperature with the furnace, grind it into powder, and then calcinate at 900°C for 16h in the muffle furnace to obtain pure phase Li ₄ Ti ₅ O ₁₂ products.

Example 4

Weigh 1.5517g (0.021mol) Li ₂ CO ₃ , 3.9935g (0.05mol) TiO ₂ , and 1.0g citric acid, shake and mix them evenly in a small plastic bottle. Weigh 0.01 g of polyacrylamide and place it in a crucible, add 5 ml of double-distilled water, and wait for it to fully dissolve to form an aqueous solution of polyacrylamide. Add the mixture of the above three into the polyacrylamide aqueous solution, and stir vigorously to form a paste-like rheological phase. In the muffle furnace, first keep the temperature at 100°C for 3h, then pre-fire at 600°C, hold the temperature for 12h, cool down to room temperature with the furnace, grind it into powder, and then calcinate in the muffle furnace at 950°C for 16h to obtain pure phase Li ₄ Ti ₅ O ₁₂ products.

The prepared product was made into an electrode sheet of a simulated battery: active materials Li ₄ Ti ₅ O ₁₂ , acetylene black, and PVDF were weighed according to a mass ratio of 80:10:10. Grind and refine Li ₄ Ti ₅ O ₁₂ and acetylene black in an agate mortar, and mix them uniformly; add a certain amount of binder solution (PVDF dissolved in an appropriate amount of N-methylpyrrolidone), and stir evenly to obtain a slurry , coated on copper foil. After drying, rolling, punching into a disc with a diameter of 10mm and weighing to make an electrode. Use metal lithium sheet as the counter electrode, Celgard2400 as the diaphragm, 1mol/L LiPF6/EC+DMC+EMC (volume ratio 1:1:1) as the electrolyte, and assemble in a glove box with dry air (relative humidity ≤ 4%) After the battery is assembled, let it stand for 24 hours.

Use Wuhan Jinnuo battery tester to test the constant current charge and discharge of the battery at room temperature. After testing and comparison, the product prepared at 850°C is better than other temperatures. It is charged and discharged at 0.1C, and the charge and discharge voltage range is 1.0-2.5V. , as can be seen from Figure 5, the first discharge specific capacity reached 170mAh/g, close to the theoretical capacity (175mAh/g). It can be seen from the XRD spectrum in Figure 1 that the diffraction peaks correspond to each other and there are no impurity peaks, indicating that a pure phase of spinel-type lithium titanate has been obtained. Accompanying drawing 2 is the SEM photo of the product obtained at different temperatures, the comparison shows that the particle size of the product obtained at 800 and 850°C is small and uniform, and the particle size of the product above 900°C becomes larger, which may be due to The high temperature agglomerates the particles.

Example 5

Weigh 1.5517g (0.021mol) Li ₂ CO ₃ , 3.9935g (0.05mol) TiO ₂ , and 0.50g activated carbon, shake and mix them evenly in a small plastic bottle. Weigh 0.01 g of polyacrylamide and place it in a crucible, add 5 ml of double-distilled water, and wait for it to fully dissolve to form an aqueous solution of polyacrylamide. Add the mixture of the above three into the polyacrylamide aqueous solution, and stir vigorously to form a paste-like rheological phase. In the muffle furnace, first keep the temperature at 100°C for 3h, then pre-fire at 600°C, hold the temperature for 12h, cool down to room temperature with the furnace, grind it into powder, and then calcinate in the muffle furnace at 850°C for 16h to obtain pure phase Li ₄ Ti ₅ O ₁₂ products.

Example 6

Weigh 1.5517g (0.021mol) Li ₂ CO ₃ , 3.9935g (0.05mol) TiO ₂ , and 1.0g glucose, shake and mix them evenly in a small plastic bottle. Weigh 0.01 g of polyacrylamide and place it in a crucible, add 5 ml of double-distilled water, and wait for it to fully dissolve to form an aqueous solution of polyacrylamide. Add the mixture of the above three into the polyacrylamide aqueous solution, and stir vigorously to form a paste-like rheological phase. In the muffle furnace, first keep the temperature at 100°C for 3h, then pre-fire at 600°C, hold the temperature for 12h, cool down to room temperature with the furnace, grind it into powder, and then calcinate in the muffle furnace at 850°C for 16h to obtain pure phase Li ₄ Ti ₅ O ₁₂ products.

It can be seen from Figure 3 that different carbonizing agents have little effect on the capacity of the product, and the specific capacity of the first charge and discharge is above 162mAh/g.

Example 7

Weigh 1.5400g (0.0208mol) Li ₂ CO ₃ , 3.9935g (0.05mol) TiO ₂ , 0.0159g (0.00015mol) Na ₂ CO ₃ , and 1.0g citric acid, shake and mix them evenly in a small plastic bottle. Weigh 0.01 g of polyacrylamide and place it in a crucible, add 5 ml of double-distilled water, and wait for it to fully dissolve to form an aqueous solution of polyacrylamide. Add the mixture of the above three into the polyacrylamide aqueous solution, and stir vigorously to form a paste-like rheological phase. In the muffle furnace, first keep the temperature at 100°C for 3 hours, then pre-fire at 600°C, hold the temperature for 12 hours, cool to room temperature with the furnace, grind it into powder, and then calcinate in the muffle furnace at 850°C for 16 hours to obtain the lithium-site Na-doped product Li _3.97 Na _0.03 Ti ₅ O ₁₂ . (The amount of doping here is very small, and the original crystal structure is not changed, so it is still lithium titanate, strictly speaking, it is metal-doped lithium titanate)

The phase analysis of the product is carried out by German buluke D8 Focus automatic X-ray diffractometer, and the XRD pattern of the product is shown in Figure 1, and the scanning range is 10-90°. Compared with the standard card (PDF-49-0207), each diffraction peak corresponds one by one, and there is no impurity peak, indicating that spinel crystals are obtained, and lithium titanate is effectively doped. It can be seen from Figure 5 that at 0.1C Charge and discharge under high temperature, the first discharge specific capacity reaches 158mAh/g, compared with the pure phase product, the capacity is slightly reduced, this may be Na doping, occupying the Li site, resulting in partial capacity loss, but as shown in Figure 6 It can be seen that the cycle performance increases, and after 30 cycles, the capacity decay is the smallest. Accompanying drawing 3 is the SEM photo of the product, the particle size is smaller, but the uniformity is not good.

Example 8

Weigh 1.5400g (0.0208mol) Li ₂ CO ₃ , 3.9935g (0.05mol) TiO ₂ , 0.0987g (0.0004mol) manganese acetate, and 1.0g citric acid, shake and mix them evenly in a small plastic bottle. Weigh 0.01 g of polyacrylamide and place it in a crucible, add 5 ml of double-distilled water, and wait for it to fully dissolve to form an aqueous solution of polyacrylamide. Add the mixture of the above three into the polyacrylamide aqueous solution, and stir vigorously to form a paste-like rheological phase. In the muffle furnace, first keep the temperature at 100°C for 3 hours, then pre-fire at 600°C, hold the temperature for 12 hours, cool down to room temperature with the furnace, grind it into powder, and then calcinate in the muffle furnace at 850°C for 16 hours to obtain the titanium-doped Mn product Li ₄ Ti _4.96 Mn _0.04 O ₁₂ .

The phase analysis of the product is carried out by German buluke D8 Focus automatic X-ray diffractometer, and the XRD pattern of the product is shown in Figure 1, and the scanning range is 10-90°. Compared with the standard card (PDF-49-0207), each diffraction peak corresponds one by one, and there is no impurity peak, indicating that the spinel crystal is obtained, and the lithium titanate is effectively doped. It can be seen from Figure 5 that the charge-discharge test was carried out at 0.1C, and the first discharge specific capacity reached 170mAh/g. It can be seen from Figure 6 that the cycle performance of the cyclic voltammetry test is better than that of the pure-phase product.

Example 9

Weigh 0.96g (0.04mol) LiOH, 3.9935g (0.05mol) TiO ₂ , and 1.0g citric acid, shake and mix them evenly in a small plastic bottle. Weigh 0.01 g of polyacrylamide and place it in a crucible, add 5 ml of double-distilled water, and wait for it to fully dissolve to form an aqueous solution of polyacrylamide. Add the mixture of the above three into the polyacrylamide aqueous solution, and stir vigorously to form a paste-like rheological phase. In the muffle furnace, first keep the temperature at 100°C for 3h, then pre-fire at 600°C, keep the temperature for 12h, cool down to room temperature with the furnace, grind it into powder, and then calcinate at 850°C for 16h in the muffle furnace to obtain pure phase Li ₄ Ti ₅ O ₁₂ products.

The prepared product is assembled into a battery, and the charge and discharge test is carried out at 0.1C. As shown in Figure 7, the first discharge specific capacity reaches more than 160mAh/g, and the capacity is slightly lower than that of the product prepared by using lithium carbonate as lithium source (being 170mAh/g). g), the difference is not big, and different lithium sources can obtain products with excellent performance.

Claims (5)

1. the preparation method of a lithium ionic cell cathode material lithium titanate is characterized by and may further comprise the steps:

With lithium source, TiO ₂Mix with carbonized agent, its material proportion is mol ratio Li: Ti=0.80～0.88: 1, mass ratio TiO ₂: carbonized agent=4～8: 1, then mixture is joined concentration and be in 0.15%～0.2% polyacrylamide (PAM) aqueous solution, its quality proportioning is polyacrylamide: TiO ₂=0.002～0.003: 1, powerful then the stirring is after mixing, with material 100 ℃ of constant temperature 3h of elder generation in retort furnace, 600 ℃ of pre-burnings, constant temperature 12h cools to room temperature with the furnace again, grind into powder, 750～950 ℃ of calcining 16h in retort furnace make product then.

2. the preparation method of lithium ionic cell cathode material lithium titanate as claimed in claim 1 is characterized by among the described preparation method, in the raw material except lithium source, TiO ₂And carbonized agent, also add Na ₂CO ₃, mol ratio Na: Ti=0.01～0.10: 5 wherein.

3. the preparation method of lithium ionic cell cathode material lithium titanate as claimed in claim 1 is characterized by among the described preparation method, in the raw material except lithium source, TiO ₂And carbonized agent, also add manganous acetate, wherein mol ratio Mn: Li=0.01～0.12: 4.

4. the preparation method of lithium ionic cell cathode material lithium titanate as claimed in claim 1, it is characterized by described lithium source is Quilonum Retard or lithium hydroxide.

5. the preparation method of lithium ionic cell cathode material lithium titanate as claimed in claim 1, it is characterized by described carbonized agent is gac, citric acid or glucose.

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