CN104916824A - Tin/oxidized graphene anode material for lithium battery and preparation method thereof - Google Patents

Abstract

The invention discloses a tin/oxidized graphene anode material for a lithium battery and a preparation method thereof. The composite anode material is formed by uniformly adhering nanosized tin to the surface of oxidized graphene. The preparation method comprises the following steps: ultrasonically dispersing oxidized graphene powder into a mixed solution of water and ethylene glycol to obtain a dispersion solution, adding nanosized tin and a dispersing agent in the dispersion solution until the nanosized tin is completely dispersed through ball-milling, and drying to obtain the composite anode material in which the flaky nanosized tin is uniformly adhered to the surface of the oxidized graphene. The composite material can be used for preparing the lithium ion battery with the characteristics of high specific discharge capacity, excellent rate performance, long cycle life and the like; and the preparation method is simple, reliable, good in process repeatability, high in operability and low in cost, and is suitable for industrial production.

Description

A kind of tin/graphene oxide negative electrode material for lithium battery and preparation method thereof

technical field

The invention relates to a tin/graphene oxide negative electrode material for lithium ion batteries and a preparation method thereof, belonging to the field of lithium ion batteries.

Background technique

Since Japan's Sony Corporation took the lead in developing and commercializing lithium-ion batteries in 1990, lithium-ion batteries have developed rapidly. Today lithium-ion batteries have been widely used in various fields of civil and military use. With the continuous advancement of science and technology, people have put forward more and higher requirements for the performance of batteries: the miniaturization and personalized development of electronic equipment requires batteries to have smaller volumes and higher specific energy output; aerospace energy requirements Batteries have cycle life, better low-temperature charge and discharge performance, and higher safety performance; electric vehicles require batteries with large capacity, low cost, high stability and safety performance.

The negative electrode materials of lithium-ion batteries include carbon materials, intermetallic compounds, tin-based compounds, and the like. At present, the anode materials of commercial lithium-ion batteries use graphite-like carbon materials, which have the advantages of low lithium intercalation/deintercalation potential, suitable reversible capacity, rich resources, and low price. They are ideal lithium-ion battery anode materials. However, its theoretical specific capacity is only 372mAh/g, which limits the further improvement of the specific energy of lithium-ion batteries, and cannot meet the growing demand for high-energy portable mobile power supplies. The lithium storage principle of tin-based alloys is similar to that of silicon-based alloys, using tin and lithium to form an alloy. The highest composition can reach the level of Li _4.4 Sn, and the theoretical capacity is 994mAh/g. But again, the volume expands to 358% after intercalating Li in Sn, which leads to the cracking of alloy particles and the degradation of electrode performance.

Graphene is currently the thinnest (0.335nm) but also the hardest nanomaterial in the world. It is almost completely transparent, with an absorption rate of only 2.3%, and a thermal conductivity as high as 5300 W/m K, which is higher than that of carbon nanotubes and diamonds. Among other carbon materials, graphene has good electronic conductivity, its electron mobility is higher than 15000cm2/V·s at room temperature, and its resistivity is only 10-6 Ω·cm, which is currently the material with the smallest resistivity in the world.

The connection between each carbon atom in graphene is very flexible. When an external mechanical force is applied, the surface of the carbon atom bends and deforms, so that the carbon atoms do not need to be rearranged to adapt to the external force, and the structure remains stable. After a lot of experiments, the research team of Columbia University in the United States found that graphene is the strongest material in the world so far. It will be able to withstand the pressure of about two tons of weight without breaking. At the same time, graphene is the strongest substance known to man, harder than diamond, and 100 times stronger than the best steel in the world.

Graphene, as a new type of two-dimensional nanomaterial, is the only two-dimensional free atomic crystal found so far. Since its discovery in 2004, graphene has not only received great attention in theoretical science, but also has been widely used in electronics, optics, magnetism, biomedicine, catalysis, energy storage and Many fields such as sensors have shown great application potential, which has attracted great attention from the scientific and industrial circles. Countries around the world have taken graphene and its application technology as a long-term strategic development direction, hoping to take the initiative and take the lead in the new round of industrial revolution triggered by graphene.

At present, the effective way to slow down the rapid capacity fading when tin is used as the negative electrode material is generally to compound the active material with other matrix materials or to synthesize the active material with specific morphology. So far, there is no technology to prepare composite materials by combining graphene oxide and Sn, and there is no relevant report on related composite materials as lithium battery anode materials.

Contents of the invention

In view of the defects existing in the existing lithium-ion battery materials, the purpose of the present invention is to provide a structure in which nano-tin with flake-like morphology is uniformly adsorbed on the surface of graphene oxide, which can be used to prepare lithium-ion batteries with high discharge specific capacity and excellent rate. Tin/graphene oxide anode composites for lithium-ion batteries characterized by high performance and long cycle life.

Another object of the present invention is to provide a method for preparing tin/graphene oxide negative electrode composite material with simple process, good repeatability, low cost and environmental friendliness.

The invention provides a tin/graphene oxide negative electrode composite material for a lithium ion battery. The composite material is composed of nanometer tin uniformly adsorbed on the surface of graphene oxide.

The mass of nano-tin in the preferred tin/graphene oxide negative electrode composite material accounts for 5-15% of the total mass of nano-tin and graphene oxide.

The shape of nano-tin in the preferred tin/graphene oxide negative electrode composite material is sheet-like, and the thickness of the sheet is 5-20 nm. The morphology of nano-tin is uniform, and the thickness can be adjusted within an appropriate range.

The nano-tin in the further preferred tin/graphene oxide negative electrode composite material is obtained by adsorbing on the surface of graphene oxide by ball milling.

The preferred specific surface area of the tin/graphene oxide negative electrode composite material is 200-600 m ² /g.

The present invention also provides a method for preparing the tin/graphene oxide negative electrode composite material. The method is to add graphene oxide powder and nano-tin in a certain proportion, add a solvent and a dispersant, and perform ball milling until the nano-tin is completely dispersed. Separation of solid and liquid by centrifugation and drying.

The method for preparing tin/graphene oxide negative electrode composite material of the present invention also comprises following preferred scheme:

In a preferred solution, the mass ratio of tin to graphene oxide is 0.05-0.5:1.

In a further preferred solution, the solvent is a mixed solution of water and ethylene glycol.

In a further preferred solution, the dispersant is at least one of cetyltrimethylammonium bromide (CTAB), lithium dodecylsulfonate (PVP), and polyvinylpyrrolidone (SDS).

The most preferred solution is: ultrasonically disperse the graphene oxide powder prepared by the improved Hummers method in a mixed solution of water and ethylene glycol to obtain a dispersion, add a dispersant, nano-tin and ball mill and mix for 10- After 24 hours, centrifuge for solid-liquid separation, and then dry to obtain the tin/graphene oxide composite material.

In a further preferred solution, drying is carried out in a vacuum oven at 60-90°C.

The graphene oxide of the present invention is prepared by the improved Hummers method: add scaly graphite with a purity of not less than 99.5% to a mixed solution of concentrated sulfuric acid and phosphoric acid, and after fully dispersing, maintain the temperature of the mixed solution at 0-5°C In between, potassium permanganate was added in batches, and stirred for 2 to 4 hours, then stirred at room temperature for 12 to 24 hours, and further stirred at 75 to 85°C for 0.5 to 1 hour to obtain a mixture; Slowly add deionized water to dilute and carry out oxidation reaction at the same time. After the reaction is completed, add hydrogen peroxide to remove potassium permanganate, separate solid and liquid, and dry to obtain graphene oxide powder.

The mass ratio of the flaky graphite to potassium permanganate is 1:1-6.

The volume ratio of the concentrated sulfuric acid and phosphoric acid is 7-5:1.

The solid-to-liquid ratio of the flaky graphite to the concentrated sulfuric acid is 1-5g: 100-350mL.

The mass ratio of the hydrogen peroxide to potassium permanganate is 0.5:1.

The tin/graphene oxide negative electrode material prepared by the present invention is used to prepare the negative electrode: the tin/graphene oxide negative electrode material is thoroughly mixed with conductive carbon black conductive agent, PVDF binder and a small amount of water to form a uniform paste, and coated The copper foil substrate was used as the test electrode, and the metal lithium was used as the counter electrode to make a button battery.

Beneficial effects of the present invention: the present invention adsorbs nano-tin on the surface of graphene oxide for the first time through physical ball milling to form a composite material. The appearance of the tin in the composite material is uniform sheet, and the thickness is controllable, which can be used to prepare Lithium-ion batteries with high discharge specific capacity, excellent rate performance and long cycle life. Compared with the prior art, the beneficial effects brought by the technical solution of the present invention are as follows:

1. The preparation method of tin/graphene oxide negative electrode composite material is simple, and it is synthesized by ball milling method, which has good repeatability, low cost, environmental friendliness, and is suitable for industrial production;

2. Graphene oxide with high electrical conductivity and mechanical strength, large specific surface area agent and porosity is used as the matrix material. Due to the dispersion and load-carrying effect of graphene oxide, tin is evenly dispersed and has a sheet structure with a thickness of 5-20nm. , the appropriate thickness of the sheet-like structure makes the composite material have a higher specific surface area, which can provide a larger reaction interface, and at the same time can alleviate the volume expansion of the material, thereby effectively improving its cycle stability during charge and discharge;

3. The layered structure of graphene oxide and tin is perfectly combined. The special structure of graphene oxide can effectively alleviate the volume change caused by the tin negative electrode of the composite material during charge and discharge, and can avoid the rapid decay of the electrode capacity of the composite material and simultaneous oxidation. Graphene can increase the conductivity of the material and make up for the deficiency of a single tin electrode;

4. Tin/graphene oxide negative electrode composite material, when used as a lithium ion battery negative electrode material, has high discharge specific capacity and good cycle performance.

Detailed ways

The following examples are intended to further describe the content of the present invention in detail; and the protection scope of the claims of the present invention is not limited by the examples.

Example 1

Take by weighing 5g of flaky graphite with a purity of 99.5%, add it into a mixed solution containing 350mL mass fraction of 98% concentrated sulfuric acid and 50mL mass fraction of 85% phosphoric acid, add 30g potassium permanganate in batches for oxidation, the The mixed solution was kept at 0° C., stirred for 2 h, then stirred in a water bath at room temperature for 12 h, and further stirred at 80° C. for 0.5 h to obtain a mixture. 350 mL of deionized water was slowly added to the mixture under ice bath conditions. After 15 minutes, add 15g of hydrogen peroxide to remove potassium permanganate, then the color of the mixture turns bright yellow, filter with suction, wash with dilute hydrochloric acid with a concentration of 10% for 3 times, filter with suction, and dry in vacuum at 60°C for 48 hours to obtain graphite oxide ene (GO).

Weigh 0.3g GO, add 20mL deionized water and 40mL ethylene glycol to ultrasonically disperse for 3 hours to form a dispersion liquid, then add 0.170g CTAB and 0.015g Sn in turn under stirring conditions, and then ball mill and mix for 24 hours to obtain a black solid, which is filtered by suction After cleaning, dry in a drying oven at 60°C to obtain the tin/graphene oxide negative electrode material of the present invention.

Weigh 0.4g of the tin/graphene oxide negative electrode composite material prepared above, add 0.05g of conductive carbon black as a conductive agent, 0.05g of PVDF as a binder, add a small amount of NMP, grind and mix thoroughly to form a uniform paste, and apply Covered on the copper foil substrate as the test electrode, the metal lithium is used as the counter electrode to make a button battery, and its electrolyte is 1mol/L LiPF6/EC+DMC+EMC (v/v=1:1:1), the test The charge and discharge current density is 500mA/g.

The electrode made of tin/graphene oxide negative electrode composite material, when discharged at a constant current of 500mA/g at room temperature, can still maintain a specific capacity of 430mAh/g after 200 cycles, showing good cycle performance.

Example 2

Take by weighing 3g of flaky graphite with a purity of 99.5%, add it to a mixed solution containing 350mL mass fraction of 98% concentrated sulfuric acid and 50mL mass fraction of 85% phosphoric acid, and add 18g potassium permanganate in batches for oxidation. The mixed solution was kept at 0° C., stirred for 2 h, then stirred in a water bath at room temperature for 12 h, and further stirred at 80° C. for 0.5 h to obtain a mixture. 350 mL of deionized water was slowly added to the mixture under ice bath conditions. After 15 minutes, add 9g of hydrogen peroxide to remove potassium permanganate, then the color of the mixture turns bright yellow, filter with suction, wash with dilute hydrochloric acid with a concentration of 10% for 3 times, filter with suction, and dry in vacuum at 60°C for 48 hours to obtain graphite oxide ene (GO).

Weigh 0.3g GO, add 40mL deionized water and 80mL ethylene glycol to ultrasonically disperse for 3 hours to form a dispersion, then add 0.170g CTAB and 0.045g Sn in turn under stirring conditions, and then ball mill and mix for 12 hours to obtain a black solid, which is filtered by suction After cleaning, dry in a drying oven at 60°C to obtain the tin/graphene oxide negative electrode composite material of the present invention.

Weigh 0.35g of the tin/graphene oxide negative electrode composite material prepared above, add 0.1g conductive carbon black as a conductive agent, 0.05g PVDF as a binder, add a small amount of NMP, grind and mix thoroughly to form a uniform paste, coat Covered on the copper foil substrate as the test electrode, the metal lithium is used as the counter electrode to make a button battery, and its electrolyte is 1mol/L LiPF6/EC+DMC+EMC (v/v=1:1:1), the test The charge and discharge current density is 500mA/g. The lithium battery electrodes prepared in this example and the lithium sheet are assembled into a button battery. When discharged at a constant current of 500mA/g at room temperature, the specific capacity can still be maintained at 510mAh/g after 200 cycles. Show good cycle performance.

Example 3

Take by weighing 5g of flaky graphite with a purity of 99.5%, add it into a mixed solution containing 300mL mass fraction of 98% concentrated sulfuric acid and 50mL mass fraction of 85% phosphoric acid, add 30g potassium permanganate in batches for oxidation, and The mixed solution was kept at 0° C., stirred for 2 h, then stirred in a water bath at room temperature for 12 h, and further stirred at 80° C. for 0.5 h to obtain a mixture. 350 mL of deionized water was slowly added to the mixture under ice bath conditions. After 15 minutes, add 15g of hydrogen peroxide to remove potassium permanganate, then the color of the mixture turns bright yellow, filter with suction, wash with dilute hydrochloric acid with a concentration of 10% for 3 times, filter with suction, and dry in vacuum at 60°C for 48 hours to obtain graphite oxide ene (GO).

Weigh 0.1g GO, add 30mL deionized water and 60mL ethylene glycol to ultrasonically disperse for 3 hours to form a suspension, then add 0.100g PVP and 0.015g Sn in turn under stirring conditions, and then ball mill and mix for 24 hours to obtain a black solid. After filtering and cleaning, put it in a drying oven at 60° C. to dry, and then the tin/graphene oxide negative electrode composite material of the present invention can be obtained.

Weigh 0.35g of the tin/graphene oxide negative electrode composite material prepared above, add 0.1g conductive carbon black as a conductive agent, 0.05g PVDF as a binder, add a small amount of NMP, grind and mix thoroughly to form a uniform paste, coat Covered on the copper foil substrate as the test electrode, the metal lithium is used as the counter electrode to make a button battery, and its electrolyte is 1mol/L LiPF6/EC+DMC+EMC (v/v=1:1:1), the test The charge and discharge current density is 500mA/g. The lithium battery electrodes prepared in this example and the lithium sheet are assembled into a button battery. When discharged at a constant current of 500mA/g at room temperature, the specific capacity can still be maintained at 480mAh/g after 200 cycles. Show good cycle performance.

Example 4

Take by weighing 5g of flaky graphite with a purity of 99.5%, add it into a mixed solution containing 350mL mass fraction of 98% concentrated sulfuric acid and 50mL mass fraction of 85% phosphoric acid, add 30g potassium permanganate in batches for oxidation, the The mixed solution was kept at 0° C., stirred for 2 h, then stirred in a water bath at room temperature for 12 h, and further stirred at 80° C. for 0.5 h to obtain a mixture. 350 mL of deionized water was slowly added to the mixture under ice bath conditions. After 15 minutes, add 15g of hydrogen peroxide to remove potassium permanganate, then the color of the mixture turns bright yellow, filter with suction, wash with dilute hydrochloric acid with a concentration of 10% for 3 times, filter with suction, and dry in vacuum at 60°C for 48 hours to obtain graphite oxide ene (GO).

Weigh 0.2g GO, add 40mL deionized water and 80mL ethylene glycol to ultrasonically disperse for 3 hours to form a dispersion liquid, then add 0.170g SDS and 0.05g Sn in turn under stirring conditions, and then ball mill and mix for 24 hours to obtain a black solid, which is filtered by suction After cleaning, dry in a drying oven at 60°C to obtain the tin/graphene oxide negative electrode composite material of the present invention.

Weigh 0.4g of the tin/graphene oxide negative electrode composite material prepared above, add 0.05g of conductive carbon black as a conductive agent, 0.05g of PVDF as a binder, add a small amount of NMP, grind and mix thoroughly to form a uniform paste, and apply Covered on the copper foil substrate as the test electrode, the metal lithium is used as the counter electrode to make a button battery, and its electrolyte is 1mol/L LiPF6/EC+DMC+EMC (v/v=1:1:1), the test The charge and discharge current density is 500mA/g. The lithium battery electrodes prepared in this example and the lithium sheet are assembled into a button battery. When discharged at a constant current of 500mA/g at room temperature, the specific capacity can still be maintained at 420mAh/g after 200 cycles. Show good cycle performance.

Example 5

Take by weighing 5g of flaky graphite with a purity of 99.5%, add it into a mixed solution containing 350mL mass fraction of 98% concentrated sulfuric acid and 50mL mass fraction of 85% phosphoric acid, add 30g potassium permanganate in batches for oxidation, the The mixed solution was kept at 0° C., stirred for 2 h, then stirred in a water bath at room temperature for 12 h, and further stirred at 80° C. for 0.5 h to obtain a mixture. 350 mL of deionized water was slowly added to the mixture under ice bath conditions. After 15 minutes, add 15g of hydrogen peroxide to remove potassium permanganate, then the color of the mixture turns bright yellow, filter with suction, wash with dilute hydrochloric acid with a concentration of 10% for 3 times, filter with suction, and dry in vacuum at 60°C for 48 hours to obtain graphite oxide ene (GO).

Weigh 0.3g GO, add 20mL deionized water and 40mL ethylene glycol to ultrasonically disperse for 3 hours to form a dispersion, then add 0.15g CTAB and 0.036g Sn in turn under stirring conditions, and then ball mill and mix for 12 hours to obtain a black solid, which is filtered by suction After cleaning, dry in a drying oven at 60°C to obtain the tin/graphene oxide negative electrode composite material of the present invention.

Weigh 0.4g of the tin/graphene oxide negative electrode composite material prepared above, add 0.05g of conductive carbon black as a conductive agent, 0.05g of PVDF as a binder, add a small amount of NMP, grind and mix thoroughly to form a uniform paste, and apply Covered on the copper foil substrate as the test electrode, the metal lithium is used as the counter electrode to make a button battery, and its electrolyte is 1mol/L LiPF6/EC+DMC+EMC (v/v=1:1:1), the test The charge and discharge current density is 500mA/g.

The lithium battery electrode prepared in this example is assembled into a button battery with a lithium sheet. When discharged at a constant current of 500mA/g at room temperature, the specific capacity can still be maintained at 460mAh/g after 200 cycles, showing good cycle performance.

Claims (7)

1. A tin/graphene oxide negative electrode composite material for lithium battery, characterized in that, it is formed on the surface of graphene oxide evenly adsorbed by nano tin. 2. The tin/graphene oxide negative electrode composite material according to claim 1, wherein the mass of the nano-tin accounts for 5-15% of the total mass of the nano-tin and graphene oxide. 3 . The tin/graphene oxide negative electrode composite material according to claim 1 , characterized in that, the nano-tin has a flake shape, and the thickness of the flakes is 5-20 nm. 4. The tin/graphene oxide negative electrode composite material according to claim 3, characterized in that, the nano-tin is obtained by being adsorbed on the surface of graphene oxide by ball milling. 5 . The tin/graphene oxide negative electrode composite material according to claim 1 , wherein the specific surface area of the tin/graphene oxide composite material is 200˜600 m ² /g. 6. The method for preparing the tin/graphene oxide negative electrode composite material described in any one of claims 1 to 5, is characterized in that, the graphene oxide powder and nano-tin are added in a certain proportion with a solvent and a dispersant, and passed through ball milling , until the nano-tin is completely dispersed, centrifuged for solid-liquid separation, and dried. 7. The method according to claim 6, characterized in that, the solvent is a mixed solvent of water and ethylene glycol, and its volume ratio is 1:2-4; the mass ratio of tin to graphene oxide is 0.05- 0.5:1; the dispersant is at least one of cetyltrimethylammonium bromide, lithium dodecylsulfonate, and polyvinylpyrrolidone.