CN105336928B - Preparation method and application of polypyrrole-coated carbon fluoride cathode material - Google Patents

Abstract

The invention discloses a preparation method and application of a polypyrrole-coated carbon fluoride positive electrode material; the preparation process of the positive electrode material is: after carbon fluoride particles are dispersed in water under the action of a surfactant, pyrrole monomer is added and mixed evenly , to obtain a carbon fluoride/pyrrole suspension; dropwise add an acidic solution containing an oxidizing agent of inorganic salts to the obtained carbon fluoride/pyrrole suspension, stir and react, and the reaction product is washed and dried in sequence to obtain the product. The preparation method is simple to operate, avoids the use of toxic organic solvents, is non-toxic and environmentally friendly, has low cost, and meets the requirements of industrial production; the polypyrrole layer of the prepared polypyrrole-coated carbon fluoride cathode material is uniformly coated and has good electrical conductivity , can improve the rate discharge performance of the primary battery.

Description

Preparation method and application of polypyrrole-coated carbon fluoride cathode material

technical field

The present invention relates to the preparation and application of primary battery positive electrode materials, in particular to a preparation method of polypyrrole (PPy) coated carbon fluoride positive electrode material and its application in the preparation of primary battery positive electrode materials, belonging to organic/inorganic composite positive electrode materials field of preparation.

Background technique

Fluorinated carbons, as a new type of energy material, are attracting more and more attention. At present, the countries that produce and apply lithium-carbon fluoride batteries in the world are mainly the United States and Japan. The National Aeronautics and Space Administration (NASA) has long put forward the theory of using fluorinated carbons as electrode active materials for lithium batteries, and has gradually formed industrialization (fluorinated carbons as battery electrode active materials, combined with non-aqueous electrolytes) The resulting battery has 6-9 times the energy of the zinc-manganese battery). In 1973, Japan also developed this kind of battery. In Japan, this kind of battery is also mainly used in civil fields such as cameras, watches and micro-memory. Studies have shown that: carbon fluoride is non-toxic, does not pollute the environment, and has no wettability, so it is a good electrode material. However, this technology field has just started in our country.

Among the primary batteries, the lithium-carbon fluoride battery is currently the battery with the largest theoretical specific energy (about 2180Wh/kg), and it is also the first solid positive lithium battery to be commercialized. Compared with other disposable batteries, lithium-carbon fluoride batteries have more advantages: (1) environmental protection and pollution-free; (2) high safety; (3) wide operating temperature range (conventional products can meet -30 ~ 80 ℃ use requirements), excellent high and low temperature performance; (4) stable working voltage; (5) low self-discharge rate, no matter in use or in normal storage, its self-discharge rate is very low, only 0.5%.

Graphite fluoride (usually expressed as (CF _x ) _n ), as a kind of fluorinated carbon, has received extensive attention due to its good performance and high quality. R.Yazami et al. reported that the theoretical specific capacity of lithium-carbon fluoride batteries is related to the fluorine content (R.Yazami, A.Hamwi, Electrochem.Commun.9(2007) 1850), the more fluorine content, the theoretical specific capacity bigger.

As the fluorine content increases, the conductivity of fluorinated carbon materials becomes lower and lower (T.Nakajima, R.Hagiwara, Electrochem.Soc.133(1986) 1761.; T.Nakajima, A.Mabuchi.Electrochem.Soc. 135 (1988) 273.), so the severe polarization of the electrode material is caused, and the battery discharge platform is lower than the theoretical discharge platform (D.Linden, T.B.Reddy (Eds.), Handbook of Batteries, third ed., McGraw-Hill , 2002 (Chapter 14.9).). When x=1, carbon fluoride becomes an insulating material (Advance Research Chemicals, Inc., Carbonfluor product brochure).

In order to obtain a lithium-carbon fluoride battery with good performance, it is necessary to find a balance point between the conductivity and the specific capacity of the lithium-carbon fluoride battery. In order to increase the conductivity of fluorocarbons, Yazami et al. (P.Lam, R.Yazami, J.Power Sources 153(2006) 354.; R.Yazami, A.Hamwi, K.Guerin, Electrochem.Commun.9(2007 ) 1850.) used fluorinated carbon with a relatively low fluorine content to make electrodes to assemble batteries, and the power capacity and low-temperature discharge performance of the battery were improved, but the specific capacity of the battery was reduced. Q. Zhang et al. (J. Power Sources 195(2010) 2914–2917) coated carbon fluoride with carbon on the surface, so the conductivity was improved, the discharge platform was raised, and the discharge rate performance was improved.

Since Heeger, MacDiarmid, and Shirakawa Hideki discovered that doped polyacetylene has metal conductivity in 1977, a series of research booms on related conductive polymers have been triggered. In 1979, Diaz and others from IBM Corporation in the United States prepared a conductive polypyrrole film with a conductivity as high as 100 S/cm. Later, conductive polyaniline and polythiophene conductive polymers were discovered one after another. Because conductive polypyrrole, polyaniline and polythiophene have good stability in air holes, they have attracted widespread attention.

Patent (CN 102558856A) proposes a method of coating fluorinated graphite with polyaniline to improve the conductivity of fluorinated graphite, but it does not apply the material to batteries. Moreover, in the preparation method proposed by this patent, methanol is used as a solvent and subsequent cleaning, and methanol has strong toxicity and volatility, which is not conducive to environmental protection and safety requirements.

Patent (CN 103022493A) proposes a method of coating fluorinated graphite with polythiophene to improve the conductivity of fluorinated graphite, but it does not apply the composite material to batteries. Moreover, in the method proposed by this patent, toxic chloroform is used as a solvent, and methanol is finally required for washing, while chloroform and methanol have strong toxicity and volatility, which are not conducive to environmental protection and are easy to cause personal injury.

H. Groult et al. deposited a layer of polypyrrole on the surface of carbon fluoride electrodes embedded in carbon rods by electrochemical deposition, which improved the discharge performance of the battery, and the discharge rate was increased to 4C, corresponding to a specific capacity of about 70mAh g ^-1 . However, this method requires carbon rods as a substrate, and can only be operated as a single unit, which is inefficient and difficult to industrialize; and at a 4C rate, the specific capacity is only about 8% of the theoretical capacity.

Contents of the invention

In view of the defects existing in the prior art, the purpose of the present invention is to provide a method for preparing a positive electrode material with a PPy layer uniformly coated with carbon fluoride particles, and having the characteristics of good stability and good electrical conductivity. The method is simple to operate, The process condition is mild, the cost is low, and the industrial production requirements are met.

Another object of the present invention is to provide the application of the polypyrrole-coated carbon fluoride positive electrode material, which can be made into a positive electrode and used in a primary battery to show the characteristics of high specific capacity and high power density.

In order to achieve the technical purpose of the present invention, the present invention provides a method for preparing polypyrrole-coated carbon fluoride positive electrode material. The preparation method is to disperse carbon fluoride particles in water under the action of a surfactant, and Add pyrrole monomer in 0.25-2 times of the carbon mass, mix well to obtain carbon fluoride/pyrrole suspension; The reaction is stirred under the temperature condition of ℃～5℃, and the reaction product is washed and dried in sequence to obtain the product.

The technical solution of the present invention adopts an oxidation method to prepare polypyrrole for the first time, and the polypyrrole is evenly coated on the surface of carbon fluoride particles, forming a dense and stable polypyrrole film on the surface of carbon fluoride particles. Compared with the existing methods for preparing polyaniline and polythiophene coated carbon fluoride particulate materials, the technical solution of the present invention effectively avoids the use of toxic media; meanwhile, it also overcomes the problem of polymer coated fluorinated particles prepared by electrochemical methods. Inhomogeneous coating of carbon particles.

The method for preparing polypyrrole-coated carbon fluoride cathode material of the present invention also includes the following preferred schemes:

In a preferred scheme, the surfactant concentration is 0.05-2.0 g/L.

In a preferred solution, the surfactant is at least one of OP-10, sucrose ester and polysorbate. The preferred surfactant is capable of fully dispersing the carbon fluoride particles uniformly.

In a preferred solution, the size distribution of carbon fluoride particles is between 2 and 20 μm, and the molar ratio of fluorine to carbon is 0.8 to 1.2.

In a preferred scheme, the acidic solution containing the inorganic salt oxidant is obtained by dissolving the inorganic salt oxidant in the acidic solution; the inorganic salt oxidant is FeCl ₃ , (NH ₄ ) ₂ S ₂ O ₈ , KIO ₃ , K ₂ Cr ₂ O ₇ at least one.

In a preferred solution, the concentration of the inorganic salt oxidizing agent in the acidic solution containing the inorganic salt oxidizing agent is 0.1 g/mL˜0.5 g/mL.

In a preferred scheme, the time for the stirring reaction is 6 to 12 hours.

In a preferred solution, carbon fluoride particles are added to an aqueous solution containing a surfactant, stirred for 0.5-2 hours, and then ultrasonically treated for 0.5-2 hours to fully disperse the carbon fluoride particles.

In a preferred scheme, argon gas is continuously introduced during the stirring reaction to remove the oxygen in the carbon fluoride/pyrrole suspension.

In a preferred solution, the fluorinated carbon particles are one or more of fluorinated coke, fluorinated graphite, fluorinated graphene, fluorinated carbon fiber, and fluorinated carbon nanotube materials.

Preferably, the acidic solution is preferably dilute hydrochloric acid. The concentration of dilute hydrochloric acid is preferably 1-3 mol/L.

Preferably, the pyrrole monomer is preferably purified by rectification before use.

In a preferred scheme, the polypyrrole-coated carbon fluoride initial product is vacuum-dried at 50-60° C. for 12-24 hours.

The invention also provides the application of the polypyrrole-coated carbon fluoride positive electrode material, which is used to prepare the positive electrode of a primary battery.

Compared with the prior art, the beneficial technical effect brought by the technical solution of the present invention:

1. For the first time in the present invention, a polypyrrole layer is evenly coated on the surface of carbon fluoride particles through a chemical oxidation synthesis method to obtain a polypyrrole-coated carbon fluoride cathode material. Compared with the carbon fluoride material, the polypyrrole-coated carbon fluoride cathode material has significantly improved electrical conductivity. The polypyrrole-coated carbon fluoride cathode material is applied to a primary lithium battery, and the discharge rate of the primary battery is increased to 6C, corresponding to a specific capacity of nearly 300mAh g ^-1 , up to 35% of the theoretical capacity, compared with the lithium-fluorine in the prior art Carbonized carbon batteries have greatly improved energy density and power density.

2. The preparation method of the present invention is non-toxic and environmentally friendly, has a simple process, and can realize batch production.

Description of drawings

Fig. 1 Schematic diagram of PPy-coated carbon fluoride cathode material.

Fig. 2 is the scanning electron micrograph of the PPy coated fluorinated graphite material and fluorinated graphite raw material that embodiment 2 makes: (a) is the scanning electron micrograph of former fluorinated graphite; (b) is the fluorinated graphite after PPy coating SEM image of graphite; (c) is a partially enlarged SEM image of (b).

3 is a transmission electron microscope image of the PPy-coated graphite fluoride cathode material prepared in Example 2.

Fig. 4 is the battery constant current discharge curve figure that the PPy coated fluorinated graphite positive electrode material and fluorinated graphite positive electrode material made in embodiment 2 are made: (a) is the discharge curve of former fluorinated graphite; (b) is PPy The discharge curve of graphite fluoride after coating; (c) is the discharge curve of the material of Comparative Example 1.

detailed description

Provide the embodiment of the present invention below, in order to further description of the present invention, rather than limit the protection scope of the claims of the present invention.

Example 1

(1) Weigh 1 g of carbon fluoride, pour it into 10 mL of deionized water dissolved in a dispersant, and make a 0.1 g/mL carbon fluoride suspension by magnetic stirring, and stir for 30 minutes to make the agglomerated large particles of carbon fluoride fully Dispersion: ultrasonically disperse the above-mentioned carbon fluoride suspension for 30 minutes to fully disperse the agglomerated carbon fluoride particles. Under the condition of 0°C, in the three-neck round-bottomed flask containing the carbon fluoride suspension, magnetic stirring is carried out, and argon gas is introduced while passing through, and 0.125g of pyrrole monomer is added to the above-mentioned carbon fluoride suspension, and continue Stir for 30 minutes to disperse the pyrrole monomer evenly. Thus, a mixed suspension of carbon fluoride/pyrrole was configured.

(2) Weigh 0.5g (NH ₄ ) ₂ S ₂ O ₈ , add it into 20mL of 2mol/L HCl solution to make (NH ₄ )S ₂ O ₄ solution with a concentration of 0.025g/mL, and stir evenly; Add the above-prepared (NH ₄ ) ₂ S ₂ O ₈ solution dropwise to the mixed suspension of carbon fluoride/pyrrole under the condition of magnetic stirring and argon protection gas, seal the mixed solution, and store at 0°C Under the condition of stirring for 6h.

(3) Suction filter the reaction product obtained in step (2), and alternately wash the precipitate with deionized water and alcohol several times until the washing solution is colorless and neutral, collect the precipitate, and dry it in vacuum at 60°C for 24 hours, The graphite fluoride/polypyrrole cathode material is obtained.

(4) Grind the carbon fluoride/polypyrrole composite positive electrode material prepared by the above process evenly, weigh 0.1g, and then weigh 0.028 g of acetylene black according to the ratio of positive electrode material: acetylene black: PVDF=7:2:1 g, PVDF0.014g, mix the above three materials evenly, add an appropriate amount of NMP solvent and stir for 12 hours, so that the three materials are fully mixed evenly. The adjusted slurry is coated on aluminum foil, then dried and cut into pieces to make battery pole pieces. Weigh the weight of the pole piece, put it into the glove box and assemble a 2016-type button lithium battery, the negative pole is a lithium piece, the electrolyte solute is 1mol/L LiPF ₆ , and the electrolyte solvent is 1:1 PC (propylene carbonate) With EC (ethylene carbonate), polyethylene diaphragm is used for the diaphragm.

(5) The battery assembled in Example 1 was compared with the battery with carbon fluoride uncoated with PPy as the positive electrode under the same conditions. It can be seen from the test results that the PPy-coated fluorinated graphite (CF _x @PPy) in Example 1 has a higher discharge platform than the original fluorinated graphite (CF _x ), the discharge specific capacity has been significantly improved, and the maximum discharge rate From 1C before coating to 4C.

Table 1

Example 2

(1) Weigh 1 g of carbon fluoride, pour it into 10 mL of deionized water dissolved in a dispersant, and make a 0.1 g/mL carbon fluoride suspension by magnetic stirring, and stir for 30 minutes to make the agglomerated large particles of carbon fluoride fully Dispersion: ultrasonically disperse the above-mentioned carbon fluoride suspension for 30 minutes to fully disperse the agglomerated carbon fluoride particles. Under the condition of 0°C, in the three-necked round-bottomed flask containing the carbon fluoride suspension, magnetic stirring is carried out, and argon gas is introduced while passing through, and 0.0625g of pyrrole monomer is added to the above carbon fluoride suspension, and continue Stir for 30 minutes to disperse the pyrrole monomer evenly. Thus, a mixed suspension of carbon fluoride/pyrrole was prepared.

(2) Weigh 0.25g (NH ₄ ) ₂ S ₂ O ₈ , add it into 10mL of 2mol/L HCl solution, make (NH ₄ )S ₂ O ₄ solution with a concentration of 0.025g/mL, and stir evenly; Add the above-prepared (NH ₄ ) ₂ S ₂ O ₈ solution dropwise to the mixed suspension of carbon fluoride/pyrrole under the condition of magnetic stirring and argon protection gas, seal the mixed solution, and store at 0°C Under the condition of stirring for 6h.

(3) Suction filter the reaction product obtained in step (2), and alternately wash the precipitate with deionized water and alcohol several times until the washing solution is colorless and neutral, collect the precipitate, and dry it in vacuum at 60°C for 24 hours, The graphite fluoride/polypyrrole cathode material is obtained.

(4) Grind the carbon fluoride/polypyrrole composite positive electrode material prepared by the above process evenly, weigh 0.1g, and then weigh 0.028 g of acetylene black according to the ratio of positive electrode material: acetylene black: PVDF=7:2:1 g, PVDF0.014g, mix the above three materials evenly, add an appropriate amount of NMP solvent and stir for 12 hours, so that the three materials are fully mixed evenly. The adjusted slurry is coated on aluminum foil, then dried and cut into pieces to make battery pole pieces. Weigh the weight of the pole piece, put it into the glove box and assemble a 2016-type button lithium battery, the negative pole is a lithium piece, the electrolyte solute is 1mol/L LiPF ₆ , and the electrolyte solvent is 1:1 PC (propylene carbonate) With EC (ethylene carbonate), polyethylene diaphragm is used for the diaphragm.

(5) The battery assembled in Example 2 was compared with the battery with carbon fluoride uncoated with PPy as the positive electrode under the same conditions. The discharge results are shown in FIG. 4 . It can be seen from the test results that the discharge platform of the PPy-coated graphite fluoride (CF _x @PPy) in Example 2 is improved compared with the original fluorinated graphite (CF _x ), and the maximum discharge rate is increased from 1C before coating to 6C .

Table 2

Comparative example 1

(1) Weigh 1 g of carbon fluoride, pour it into 10 mL of deionized water dissolved in a dispersant, and make a 0.1 g/mL carbon fluoride suspension by magnetic stirring, and stir for 30 minutes to make the agglomerated large particles of carbon fluoride fully Dispersion: ultrasonically disperse the above-mentioned carbon fluoride suspension for 30 minutes to fully disperse the agglomerated carbon fluoride particles. Under the condition of 0°C, in the three-necked round-bottomed flask containing the carbon fluoride suspension, magnetic stirring is carried out, and argon gas is passed into it, and 0.5 g of pyrrole monomer is added to the above carbon fluoride suspension, and the Stir for 30 minutes to disperse the pyrrole monomer evenly. Thus, a mixed suspension of carbon fluoride/pyrrole was configured.

(2) Weigh 2g of (NH ₄ ) ₂ S ₂ O ₈ , add it into 80mL of 2mol/L HCl solution to prepare a (NH ₄ )S ₂ O ₄ solution with a concentration of 0.025g/mL, and stir evenly; The above-prepared (NH ₄ ) ₂ S ₂ O ₈ solution was added dropwise to the mixed suspension of carbon fluoride/pyrrole under the condition of magnetic stirring and argon protective gas, and the mixed solution was sealed and kept at 0°C Under stirring for 6h.

(3) Suction filter the reaction product obtained in step (2), and alternately wash the precipitate with deionized water and alcohol several times until the washing solution is colorless and neutral, collect the precipitate, and dry it in vacuum at 60°C for 24 hours, The graphite fluoride/polypyrrole cathode material is obtained.

(4) Grind the carbon fluoride/polypyrrole composite positive electrode material prepared by the above process evenly, weigh 0.1g, and then weigh 0.028 g of acetylene black according to the ratio of positive electrode material: acetylene black: PVDF=7:2:1 g, PVDF0.014g, mix the above three materials evenly, add an appropriate amount of NMP solvent and stir for 12 hours, so that the three materials are fully mixed evenly. The adjusted slurry is coated on aluminum foil, then dried and cut into pieces to make battery pole pieces. Weigh the weight of the pole piece, put it into the glove box and assemble a 2016-type button lithium battery, the negative pole is a lithium piece, the electrolyte solute is 1mol/L LiPF ₆ , and the electrolyte solvent is 1:1 PC (propylene carbonate) With EC (ethylene carbonate), polyethylene diaphragm is used for the diaphragm.

(5) Comparative example 1 (CF _x : pyrrole monomer = 2:1) because the mass of added pyrrole monomer is outside the selected range, the polypyrrole coated on the surface of CF _x is too thick, hindering the transfer of Li ⁺ . The material obtained in this comparative example was assembled into a battery, and compared with Example 2 for discharge test. It can be seen from the test results that the maximum discharge rate of the PPy-coated graphite fluoride (CF _x @PPy) cathode material in Comparative Example 1 is only 2C.

table 3

Claims (6)

1. A preparation method for polypyrrole-coated carbon fluoride cathode material, characterized in that: carbon fluoride particles are added to an aqueous solution containing a surfactant, stirred for 0.5h to 2h, and then ultrasonically treated for 0.5 to 2h to make After the carbon fluoride particles are fully dispersed, add pyrrole monomer in an amount of 0.25 to 2 times the mass of the carbon fluoride, and mix well to obtain a carbon fluoride/pyrrole suspension; add dropwise to the obtained carbon fluoride/pyrrole suspension The acidic solution containing inorganic salt oxidizing agent is stirred and reacted at 0°C to 5°C, and the reaction product is washed and dried in sequence to obtain the product; the concentration of the surfactant is 0.05 to 2.0g/L; the The surfactant is at least one of OP-10, sucrose ester and polysorbate. 2. The preparation method of polypyrrole-coated carbon fluoride cathode material according to claim 1, characterized in that: the particle size distribution of the carbon fluoride particles is between 2 and 20 μm, and the fluorocarbon molar ratio is 0.8 to 20 μm. 1.2. 3. The preparation method of polypyrrole-coated carbon fluoride cathode material according to claim 1, characterized in that: the acidic solution containing the inorganic salt oxidant is obtained by dissolving the inorganic salt oxidant in the acidic solution; The above-mentioned inorganic salt oxidizing agent is at least one of FeCl ₃ , (NH ₄ ) ₂ S ₂ O ₈ , KIO ₃ , and K ₂ Cr ₂ O ₇ . 4. The preparation method of polypyrrole-coated carbon fluoride cathode material according to claim 3, characterized in that: the concentration of the inorganic salt oxidizing agent in the acidic solution containing the inorganic salt oxidizing agent is 0.1 g/mL～ 0.5g/mL. 5 . The preparation method of polypyrrole-coated carbon fluoride cathode material according to claim 1 , characterized in that: the stirring reaction time is 6-12 hours. 6. The preparation method of polypyrrole-coated carbon fluoride positive electrode material according to claim 1, characterized in that: argon gas is continuously introduced during the stirring reaction process to remove oxygen in the carbon fluoride/pyrrole suspension.