CN101339992B - Preparation method of lithium vanadium silicate lithium ion battery cathode material - Google Patents

Abstract

The invention discloses a preparation method of vanadium lithium silicate, which belongs to the technical field of energy material preparation. Its preparation method is to first make a precursor through sol-gel reaction of lithium source, vanadium source, silicon source and carbon source, after drying, under the protection of an inert and reducing atmosphere, it undergoes high-temperature heat treatment at 600-900°C for 8-48 hours to obtain silicon Lithium vanadium oxide powder. The obtained lithium vanadium silicate powder is composed of nano-scale particles, has good electrical conductivity and high specific capacity. At 1C rate, the reversible specific capacity is greater than 160mAh/g in the range of 3-4.8V charge and discharge, and the reversible specific capacity is greater than 285mAh/g in the range of 1.5-4.8V charge and discharge, and the cycle performance is excellent, which has application prospects.

Description

Preparation method of lithium vanadium silicate lithium ion battery cathode material

technical field

The invention belongs to the technical field of energy materials. In particular, it relates to a preparation method of lithium vanadium silicate, a cathode material of a lithium ion battery.

Background technique

Lithium-ion battery is a new generation of green high-energy battery. It has many advantages such as high voltage, high energy density, good cycle performance, small self-discharge, no memory effect, and wide operating temperature range. It is widely used in mobile phones, notebook computers, UPS, Camcorders, various portable electric tools, electronic instruments, weapons and equipment, etc. also have good application prospects in electric vehicles, and are considered to be high-tech products that are of great significance to the national economy and people's lives in the 21st century.

Cathode materials are an important part of lithium-ion batteries. At present, most of the research work is concentrated on lithium intercalation compounds of six variable-valence transition metal elements Ti, V, Mn, Fe, Co, and Ni in the fourth period. The first generation of cathode materials are metal sulfides, such as TiS ₂ , MoS ₂ and so on. The second-generation cathode materials are lithium-transition metal composite oxides, represented by LiCoO ₂ , including LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiV ₃ O ₈ , LiNi _x Co _1-x O ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ and various derivatives. LiCoO ₂ is a cathode material that has been commercialized on a large scale. The research is relatively mature and has excellent comprehensive performance, but it is expensive, has low capacity, high toxicity, and certain safety problems. It is expected to be favored by new materials with high performance and low cost. replace. LiNiO ₂ has low cost and high capacity, but it is difficult to prepare, the consistency and reproducibility of material properties are poor, and there are serious safety problems. Spinel LiMn ₂ O ₄ has low cost and good safety, but has poor cycle performance, especially high temperature cycle performance, has certain solubility in electrolyte, and has poor storage performance. Research and development of new cathode materials has become a current hot spot. The third-generation cathode material is a polyanionic compound material represented by lithium iron phosphate (LiFePO ₄ ). Polyanionic compounds are a general term for a series of compounds containing tetrahedral or octahedral anionic structural units (XO _m ) ^n- (X=P, Si, B, S, As, Mo, W, etc.). Compared with lithium-transition metal composite oxide materials, polyanionic compound cathode materials generally have outstanding advantages such as stable crystal structure, good thermal stability, and excellent safety performance. People have conducted in-depth research on the phosphate series materials, and found that lithium iron phosphate (LiFePO ₄ ) and lithium vanadium phosphate (Li ₃ V ₂ (PO ₄ ) ₃ ) have excellent comprehensive properties. Especially LiFePO ₄ has been accepted by many battery companies and is widely used in power and energy storage lithium-ion batteries.

Recently, silicate series materials have gradually attracted people's attention. Because silicon is much more abundant than phosphorus in the Earth's crust, silicate materials are expected to be less costly than phosphates. In addition, silicate is ubiquitous in the earth's crust and has a very stable structure. It is expected that silicate materials will have more excellent stability than phosphate materials. Preliminary studies have been carried out on lithium manganese silicate (Li ₂ MnSiO ₄ ), lithium iron silicate (Li ₂ FeSiO ₄ ), lithium cobalt silicate (Li ₂ CoSiO ₄ ), and lithium nickel silicate (Li ₂ NiSiO ₄ ). Research.

V is a transition metal element with rich valence states, and its chemical properties are lively and diverse. Compared with other transition metals, vanadium polyanion compound battery materials have a great research space. The battery materials of vanadium polyanion compounds reported in the literature are mainly phosphates, such as Li ₃ V ₂ (PO ₄ ) ₃ , LiVPO ₄ F, VOPO ₄ , LiVOPO _{4 ,} etc., which can be used as cathode materials for lithium-ion batteries. So far, lithium vanadium silicate cathode materials have not been reported in the literature.

We envisioned using SiO ₄ ^4- ions to replace PO ₄ ^3- in Li ₃ V ₂ (PO ₄ ) ₃ , and considering the valence change of anions and ion charge balance, we designed the Li ₆ V ₂ (SiO ₄ ) ₃ new material. The molecular weight of this material is almost the same as that of Li ₃ V ₂ (PO ₄ ) ₃ , but theoretically each molecule can release 6 lithiums, so it is expected to have a higher specific capacity than Li ₃ V ₂ (PO ₄ ) ₃ . Studies have shown that the crystal structure of this new material is very similar to Li ₃ V ₂ (PO ₄ ) ₃ , as shown in the X-ray diffraction pattern in Figure 1.

The invention proposes a method for preparing a novel lithium-ion battery anode material, lithium vanadium silicate (Li ₆ V ₂ (SiO ₄ ) ₃ ).

Contents of the invention

The purpose of the present invention is to provide a method for preparing lithium vanadium silicate lithium ion battery anode material with simple process and low cost, which is characterized in that lithium source, vanadium source, silicon source and carbon source are prepared by sol-gel reaction. After drying, under the protection of an inert and reducing atmosphere, heat treatment at 600-900°C for 8-48 hours to obtain lithium vanadium silicate; the obtained lithium vanadium silicate powder is composed of nano-sized particles, with good conductivity and specific capacity high.

The vanadium source is one or more of vanadium pentoxide and ammonium metavanadate, and is formulated into a solution or slurry with a vanadium concentration of 0.2-3 mol/liter.

The lithium source is one or more of lithium carbonate or lithium hydroxide, and is formulated into a solution or slurry with a lithium concentration of 0.2-3 mol/liter.

The silicon source is one or more of nanometer silicon dioxide or tetraethyl orthosilicate, and is formulated into a solution or slurry with a silicon concentration of 0.2-3 mol/liter.

The molar ratio of the vanadium source, lithium source and silicon source used is lithium:vanadium:silicon=6:2:3.

The carbon source is selected from one or more of citric acid, ethylene glycol, sucrose, and glucose.

The mixed gas of the inert and reducing atmosphere is a mixed gas of 90% nitrogen + 10% hydrogen.

The beneficial effect of the present invention is that the preparation method prepares nano-scale lithium vanadium silicate cathode material. At 1C rate, the reversible specific capacity is greater than 160mAh/g in the range of 3-4.8V charge and discharge, and the reversible specific capacity is greater than 285mAh/g in the range of 1.5-4.8V charge and discharge, and the cycle performance is excellent, which has application prospects. The lithium vanadium phosphate cathode material prepared under the same conditions has a reversible specific capacity of 147mAh/g in the charge and discharge range of 3-4.8V and a reversible specific capacity of 243mAh/g in the charge and discharge range of 1.5-4.8V at 1C rate.

Description of drawings

Fig. 1 is an X-ray diffraction pattern of lithium vanadium phosphate (Li ₃ V ₂ (PO ₄ ) ₃ ) and lithium vanadium silicate (Li ₆ V ₂ (SiO ₄ ) ₃ ).

Detailed ways

The invention provides a method for preparing lithium vanadium silicate, a positive electrode material of a lithium ion battery, with simple process and low cost. Its specific implementation method comprises the following steps in turn:

1. Prepare a lithium source solution or slurry with a concentration of 0.2-3 mol/liter.

2. Prepare a vanadium source solution or slurry with a concentration of 0.2-3 mol/liter.

3. Prepare a silicon source solution or slurry with a concentration of 0.2-3 mol/liter.

4. Mix the above three solutions or slurries according to lithium: vanadium: silicon = 6:2:3 (molar ratio), stir and react, control the reaction temperature at 35-90°C, and gradually evaporate the solvent to form a gel-like mixture .

5. Dry the material obtained in step (4) in a dryer at 80-100° C. for 2-4 hours to obtain a lithium vanadium silicate precursor.

6. Put the product obtained in step (5) in a furnace, and under the protection of an inert and reducing atmosphere or an inert and reducing atmosphere, heat up to 600-900°C, keep the temperature at a constant temperature for 8-48 hours, and cool naturally in the furnace to obtain vanadium silicate lithium.

In the above preparation method, the lithium source described in step (1) is one or more of lithium carbonate or lithium hydroxide.

In the above preparation method, the vanadium source in step (2) is one or more of vanadium pentoxide and ammonium metavanadate.

In the above preparation method, the silicon source in step (3) is one or more of nano silicon dioxide or tetraethyl orthosilicate.

In the above preparation method, when the step (4) prepares the vanadium lithium silicate precursor, the carbon source mixed simultaneously is selected from one or more of citric acid, ethylene glycol, sucrose, glucose, and its consumption is silicon 0.5-30 wt% of lithium vanadium acid.

In the above preparation method, the inert and reducing atmosphere gas source in step (6) is a mixed gas of nitrogen and hydrogen, preferably a mixed gas of 90% nitrogen+10% hydrogen.

Introduce the embodiment of the present invention below:

Example 1

Dissolve 2.5176g of lithium hydroxide in 25ml of deionized water, dissolve 2.3396g of ammonium metavanadate in 25ml of deionized water, disperse 1.8g of nano-silicon dioxide with 25ml of ethanol to make a slurry, mix the above three, and magnetically After stirring for 1 hour, add 8.4056g of citric acid and 9.9312g of ethylene glycol, keep stirring and control the temperature of the mixture at 80°C, and gradually evaporate the solvent until the mixture becomes a uniform and stable gel. The product was dried in a drying oven at 100° C. for 2 hours to obtain a lithium vanadium silicate material precursor. Put the dried precursor into an alumina crucible, heat up to 800°C in a tube furnace, keep the temperature constant for 20 hours, and cool down with the furnace; during this process, a mixture of 90% nitrogen + 10% hydrogen is continuously fed into the tube furnace gas to obtain lithium vanadium silicate (Li ₆ V ₂ (SiO ₄ ) ₃ ) product. Using a lithium sheet as the negative electrode, tested at room temperature and 1C rate, the lithium vanadium silicate positive electrode material has a reversible specific capacity of 166mAh/g in the charge and discharge range of 3-4.8V, and a reversible specific capacity in the charge and discharge range of 1.5-4.8V. 291mAh/g.

Example 2

Dissolve 2.5176g of lithium hydroxide in 25ml of deionized water, disperse 3.6376g of vanadium pentoxide with 25ml of deionized water to make a slurry, dissolve 6.24g of ethyl orthosilicate in 25ml of deionized water, and mix the above three Mix, stir magnetically for 1 hour, add 8.4056g citric acid and 9.9312g ethylene glycol, keep stirring and control the temperature of the mixture at 60°C, and gradually evaporate the solvent until the mixture becomes a uniform and stable gel. The product was dried in a drying oven at 80° C. for 3 hours to obtain a lithium vanadium silicate material precursor. Put the dried precursor into an alumina crucible, heat up to 700°C in a tube furnace, keep the temperature constant for 36 hours, and cool down with the furnace; during this process, a mixture of 90% nitrogen + 10% hydrogen is continuously fed into the tube furnace gas to obtain lithium vanadium silicate (Li ₆ V ₂ (SiO ₄ ) ₃ ) product. Using a lithium sheet as the negative electrode, tested at room temperature and 1C rate, the reversible specific capacity of the lithium vanadium silicate positive electrode material is 161mAh/g in the charge and discharge range of 3-4.8V, and the reversible specific capacity in the charge and discharge range of 1.5-4.8V is 288mAh/g.

Example 3

5.76g of lithium carbonate was dispersed with 25ml of deionized water to make a slurry, 3.6376g of vanadium pentoxide was dispersed with 25ml of deionized water to make a slurry, and 1.8g of nano silicon dioxide was dispersed with 25ml of ethanol to make a slurry. Mix the above three, add 6.5g of glucose after magnetic stirring for 1 hour, keep stirring and control the temperature of the mixture at 70°C, and gradually evaporate the solvent until the mixture becomes a uniform and stable gel. The product was dried in a drying oven at 80° C. for 3 hours to obtain a lithium vanadium silicate material precursor. Put the dried precursor into an alumina crucible, heat up to 900°C in a tube furnace, keep the temperature constant for 8 hours, and cool down with the furnace; during this process, a mixture of 90% nitrogen and 10% hydrogen is continuously fed into the tube furnace gas to obtain lithium vanadium silicate (Li ₆ V ₂ (SiO ₄ ) ₃ ) product. Using a lithium sheet as the negative electrode, tested at room temperature and 1C rate, the lithium vanadium silicate positive electrode material has a reversible specific capacity of 162mAh/g in the charge and discharge range of 3-4.8V, and a reversible specific capacity in the charge and discharge range of 1.5-4.8V. 289mAh/g.

Example 4

Disperse 5.76g of lithium carbonate with 25ml of deionized water to make a slurry, disperse 3.6376g of vanadium pentoxide with 25ml of deionized water to make a slurry, dissolve 6.24g of ethyl orthosilicate in 25ml of deionized water, and The aforementioned three were mixed, and after magnetic stirring for 1 hour, 10.5 g of sucrose was added, and the temperature of the mixed solution was kept at 90°C under continuous stirring, so that the solvent was gradually evaporated until the mixed solution became a uniform and stable gel. The product was dried in a drying oven at 80° C. for 3 hours to obtain a lithium vanadium silicate material precursor. Put the dried precursor into an alumina crucible, heat up to 600°C in a tube furnace, keep the temperature constant for 48 hours, and cool down with the furnace; during this process, a mixture of 90% nitrogen + 10% hydrogen is continuously fed into the tube furnace gas to obtain lithium vanadium silicate (Li ₆ V ₂ (SiO ₄ ) ₃ ) product. Using a lithium sheet as the negative electrode, tested at room temperature and 1C rate, the lithium vanadium silicate positive electrode material has a reversible specific capacity of 162mAh/g in the charge and discharge range of 3-4.8V, and a reversible specific capacity in the charge and discharge range of 1.5-4.8V. 289mAh/g.

Comparative Example 1 Preparation of Lithium Vanadium Phosphate (Li ₃ V ₂ (PO ₄ ) ₃ )

Dissolve 1.2588g of lithium hydroxide in 25ml of deionized water, dissolve 2.3396g of ammonium metavanadate in 25ml of deionized water, dissolve 3.45g of ammonium dihydrogen phosphate in 25ml of deionized water, mix the above three, and stir magnetically for 1 Add 8.4056g of citric acid and 9.9312g of ethylene glycol after 1 hour, keep stirring and control the temperature of the mixed solution to be 80°C, and gradually evaporate the solvent until the mixed solution becomes a uniform and stable gel. The product was dried in a drying oven at 100° C. for 2 hours to obtain a lithium vanadium phosphate material precursor. Put the dried precursor into an alumina crucible, heat up to 800°C in a tube furnace, keep the temperature constant for 20 hours, and cool down with the furnace; during this process, a mixture of 90% nitrogen + 10% hydrogen is continuously fed into the tube furnace gas to obtain lithium vanadium phosphate (Li ₃ V ₂ (PO ₄ ) ₃ ) product. Using lithium sheet as negative electrode, tested at room temperature and 1C rate, the lithium vanadium phosphate positive electrode material has a reversible specific capacity of 147mAh/g in the charge and discharge range of 3-4.8V, and a reversible specific capacity of 243mAh in the charge and discharge range of 1.5-4.8V /g. The X-ray diffraction patterns of the obtained lithium vanadium phosphate (Li ₃ V ₂ (PO ₄ ) ₃ ) and lithium vanadium silicate (Li ₆ V ₂ (SiO ₄ ) ₃ ) are shown in FIG. 1 .

Claims (6)

1. the preparation method of a lithium ionic cell positive electrode material vanadium lithium silicate, it is characterized in that: lithium is pressed in lithium source, silicon source and vanadium source: vanadium: silicon=6: 2: 3 (mol ratio) mixes, and and be selected from citric acid, ethylene glycol, sucrose, the glucose more than one and mix as carbon source, its carbon source consumption is the 0.5-30wt% of vanadium lithium silicate, make presoma by solgel reaction, dry back obtained the vanadium lithium silicate powder in high-temperature heat treatment 8-48 hour through 600-900 ℃ under inertia and protection of reducing atmosphere; Gained vanadium lithium silicate powder is made up of nano-scale particle, good conductivity, specific capacity height.

2. according to the preparation method of the described lithium ionic cell positive electrode material vanadium lithium silicate of claim 1, it is characterized in that this method comprises following each step:

1) lithium source, silicon source and vanadium source are mixed with solution or the slurry that concentration is the 0.2-3 mol respectively;

2) in lithium: vanadium: silicon=6: 2: 3 (mol ratio) ratio, above-mentioned three kinds of solution or slurry are mixed, mix carbon source simultaneously, consumption is the 0.5-30wt% of vanadium lithium silicate, continues stirring reaction, and control reaction temperature is 35-90 ℃, solvent is evaporated gradually, generate gelatinous mixture;

3) with step 2) the gained gelatinous mixture in drier in 80-100 ℃ of dry 2-4 hour, the vanadium lithium silicate presoma;

4) step 3) gained vanadium lithium silicate presoma is placed stove, under inertia and protection of reducing atmosphere, be warming up to 600-900 ℃, constant temperature 8-48 hour, natural cooling in stove obtained the vanadium lithium silicate powder.

3. according to the preparation method of claim 1 or 2 described lithium ionic cell positive electrode material vanadium lithium silicates, it is characterized in that: described lithium source be in lithium carbonate or the lithium hydroxide more than one.

4. according to the preparation method of claim 1 or 2 described lithium ionic cell positive electrode material vanadium lithium silicates, it is characterized in that: described vanadium source is more than one in vanadic oxide, the ammonium metavanadate.

5. according to the preparation method of claim 1 or 2 described lithium ionic cell positive electrode material vanadium lithium silicates, it is characterized in that: described silicon source is more than one in silicon dioxide or the tetraethoxysilane.

6. according to the preparation method of claim 1 or 2 described lithium ionic cell positive electrode material vanadium lithium silicates, it is characterized in that: described inertia and reducing atmosphere are the mist of 90% nitrogen+10% hydrogen.

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