CN110797581B - A composite gel polymer electrolyte based on ultra-high specific surface area porous carbon material and its preparation method and application - Google Patents

Abstract

The invention discloses a composite gel polymer electrolyte based on an ultra-high specific surface area porous carbon material and a preparation method and application thereof. The method is as follows: firstly adopting sodium citrate, cobalt nitrate and potassium ferricyanide to perform hydrothermal reaction to prepare solid powder, calcining the solid powder at high temperature and foaming in acid to prepare a porous structure carbon material, and then mixing the porous structure carbon material with polyvinylidene fluoride The ethylene-hexafluoropropylene copolymer is compounded to prepare a polymer film, and finally the polymer film is activated in an electrolyte to obtain a porous carbon material composite gel polymer electrolyte. The invention utilizes the metal frame structure to prepare the porous carbon material, and then further etches to prepare the porous carbon material with ultra-high specific surface area. After being compounded with the gel electrolyte, the liquid absorption rate of the gel electrolyte can be greatly improved, and the ionization rate of the electrolyte membrane can be effectively improved. conductivity.

Description

A composite gel polymer electrolyte based on ultra-high specific surface area porous carbon materials and Its preparation method and application

technical field

The invention belongs to the technical field of batteries, and in particular relates to a composite gel polymer electrolyte based on an ultra-high specific surface area porous carbon material and a preparation method and application thereof.

Background technique

Due to its high energy density, no memory effect, low price, green and pollution-free and many other advantages, lithium-ion batteries are widely used as mobile power sources in 3C electronic products such as mobile phones, notebook computers, and digital cameras, and as power sources in automobiles. , ships, etc., as energy storage batteries for wind power, solar power, signal tower backup power, etc. At present, lithium-ion batteries have successfully occupied the 3C product market, but their performance in the field of electric vehicles is far from satisfactory. A number of recent car fires have raised considerable concerns about lithium-ion batteries. Battery safety issues are caused by different reasons, such as overcharge, abuse, short circuits inside or outside the battery, which are all related to the use of volatile, flammable, and toxic liquid organic carbonate-based electrolytes.

Compared with traditional organic carbonate-based electrolytes, solid polymer electrolytes have some obvious advantages, mainly in terms of non-volatility, low flammability, no electrolyte leakage, easy processing, and high mechanical strength. In addition, solid polymer electrolytes can use metallic lithium as the negative electrode, thereby exhibiting high energy density.

However, the all-solid polymer electrolyte has low conductivity at room temperature, and the contact between the electrode and the electrolyte is extremely poor, and the solubility of the electrolyte salt in the polymer matrix is low. When the battery is charged, the low electrolyte salt solubility can cause serious Polarization causes crystallization of electrolyte salts near the electrodes. On the other hand, gel polymer electrolytes utilize liquid electrolyte molecules immobilized in the microstructure to achieve ionic conduction, resulting in higher electrical conductivity. The composite inorganic nanomaterials can further improve the mechanical strength, electrical conductivity and other properties of the gel polymer electrolyte. At present, the composite inorganic nanomaterials such as silica and alumina have low porosity, which makes the amount of liquid electrolyte adsorbed in the gel electrolyte larger than that of the gel electrolyte. less, high conductivity cannot be achieved.

SUMMARY OF THE INVENTION

In order to solve the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a method for preparing a composite gel polymer electrolyte based on an ultra-high specific surface area porous carbon material.

Another object of the present invention is to provide a composite gel polymer electrolyte based on a porous carbon material with an ultra-high specific surface area prepared by the above method.

Another object of the present invention is to provide the application of the above-mentioned composite gel polymer electrolyte based on a porous carbon material with an ultra-high specific surface area.

The object of the present invention is achieved through the following technical solutions:

A preparation method based on ultra-high specific surface area porous carbon material composite gel polymer electrolyte, comprising the following steps:

(1) dissolving sodium citrate and cobalt nitrate in ethanol aqueous solution, adding potassium ferricyanide aqueous solution, stirring evenly, then hydrothermally reacting at 100～120 ° C for 10～24 hours, centrifugal washing, drying to obtain solid powder;

(2) calcining the solid powder at a constant temperature of 500-700° C. for 3-6 hours to obtain a porous structure cobalt oxide iron-carbon composite electrode material;

(3) soaking the porous structure cobalt oxide iron carbon composite electrode material in an acid solution, washing, filtering, and drying to obtain a porous structure carbon material;

(4) Dissolving the porous structure carbon material and the polyvinylidene fluoride-hexafluoropropylene copolymer in an organic solvent, mixing uniformly to obtain a colloid, volatilizing and removing the solvent to obtain a polymer film, and activating the polymer film in an electrolyte Then, the porous carbon material composite gel polymer electrolyte is obtained.

Preferably, the molar ratio of potassium ferricyanide in the aqueous solution of sodium citrate, cobalt nitrate and potassium ferricyanide in step (1) is (5-10):(3-10):1.

Preferably, the concentrations of sodium citrate and cobalt nitrate in the aqueous ethanol solution in step (1) are both 0.1-0.5 mol/L; preferably 0.15-0.25 mol/L.

Preferably, the volume ratio of ethanol to water in the aqueous ethanol solution in step (1) is 1:(1-5).

Preferably, the concentration of the potassium ferricyanide aqueous solution in step (1) is 0.1-0.4 mol/L, preferably 0.1-0.2 mol/L.

Preferably, the time of the hydrothermal reaction in step (1) is 10-12 h.

Preferably, the drying temperature in step (1) is 80-120° C., and the drying is carried out to constant weight.

Preferably, the washing liquid used in the centrifugal washing in step (1) is water, and the washing is performed 1 to 5 times.

Preferably, the roasting in step (2) is performed in a muffle furnace.

Preferably, the roasting temperature in step (2) is 600-700° C., and the time is 5-6 h.

Preferably, the porous-structured cobalt-iron-carbon composite electrode material in step (3) is completely immersed in an acid solution.

Preferably, the acid solution in step (3) is an aqueous hydrochloric acid solution with a concentration of 1-4 mol/L, preferably an aqueous hydrochloric acid solution with a concentration of 1-2 mol/L.

Preferably, the soaking time of step (3) is 12-36 hours.

Preferably, the washing liquid used in the washing in step (3) is water, the drying temperature is 80-120° C., and the time is 6-24 h.

Preferably, the mass ratio of the porous structure carbon material to the polyvinylidene fluoride-hexafluoropropylene copolymer in step (4) is (1-10):100, preferably (5-8):100.

Preferably, the mass ratio of the porous structure carbon material to the organic solvent in step (4) is 1:(5-20).

Preferably, the organic solvent in step (4) is N-N methylformamide.

Preferably, the method for volatilizing and removing the solvent in step (4) is as follows: uniformly coating the colloidal substance on the flat plate, and volatilizing and removing the solvent at room temperature.

Preferably, the polymer film in step (4) is completely immersed in the electrolyte.

Preferably, the electrolyte in step (4) is a carbonate solution containing 1-1.2 mol/L lithium hexafluorophosphate. The solvent of the electrolyte is a mixed solvent of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate with a volume ratio of 1:1:1.

Preferably, the activation time of step (4) is 2-10 h.

A composite gel polymer electrolyte based on ultra-high specific surface area porous carbon material prepared by the above method.

Application of the above-mentioned composite gel polymer electrolyte based on ultra-high specific surface area porous carbon material in the field of batteries.

Preference is given to applications in the field of lithium-ion batteries.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

The invention utilizes the metal frame structure to prepare the porous carbon material, and then further etches to prepare the porous carbon material with ultra-high specific surface area. After being compounded with the gel electrolyte, the liquid absorption rate of the gel electrolyte can be greatly improved, and the ionization rate of the electrolyte membrane can be effectively improved. conductivity.

Description of drawings

FIG. 1 is a transmission electron microscope image of the porous structure carbon material prepared in Example 1, wherein the right image is a partial enlarged image of the left image.

FIG. 2 is the adsorption and desorption curves of the porous carbon materials prepared in Examples 1-2.

3 is a graph showing the pore size distribution of the porous carbon materials prepared in Examples 1-2.

4 is a scanning electron microscope image of the gel electrolyte membrane prepared in Comparative Example 1.

5 is a scanning electron microscope image of the gel electrolyte membrane prepared in Example 1.

6 is a scanning electron microscope image of the gel electrolyte membrane prepared in Example 2.

FIG. 7 is the AC impedance spectrum of the gel electrolyte membranes prepared in Comparative Example 1 and Examples 1-2.

8 is the galvanostatic charge-discharge curves of the gel electrolyte membranes prepared in Comparative Example 1 and Examples 1-2 at a current density of 10 mA/g.

FIG. 9 is the discharge performance curves of the gel electrolyte membranes prepared in Comparative Example 1 and Examples 1-2 under different current densities.

FIG. 10 is the cycle performance curves of the gel electrolyte membranes prepared in Comparative Example 1 and Examples 1-2 at a current density of 100 mA/g.

Detailed ways

The present invention will be described in further detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

If the specific conditions are not indicated in the examples of the present invention, the conventional conditions or the conditions suggested by the manufacturer are used. The raw materials, reagents, etc., which are not specified by the manufacturer, are all conventional products that can be purchased from the market.

Example 1

(1) 100 milliliters of 0.5mol/L sodium citrate ethanol aqueous solutions are mixed with 100 milliliters of 0.3mol/L cobalt nitrate ethanol aqueous solutions, wherein the volume ratio of ethanol and water is 1:1, and then 50 milliliters of 0.2mol are added dropwise /L potassium ferricyanide aqueous solution, stir evenly, put the mixed solution into the reaction kettle, seal it, and conduct hydrothermal reaction at 100 °C for 12 hours. to constant weight to obtain a purple solid powder.

(2) After calcining the purple solid powder at a high temperature of 700° C. in a muffle furnace for 6 hours, a black porous structure cobalt oxide iron carbon composite electrode material is obtained.

(3) The black porous structure cobalt oxide iron carbon composite electrode material was completely immersed in 2 mol/L hydrochloric acid aqueous solution for 24 hours, then washed with deionized water, filtered, and dried at 100 °C for 12 hours to obtain a black porous structure carbon material.

(4) Dissolve the black porous structure carbon material and polyvinylidene fluoride-hexafluoropropylene copolymer in N-methylformamide in a mass ratio of 8:100 (according to the mass ratio of porous structure carbon material and N-methylformamide) 1:10 preparation), stir to obtain a uniform colloid, spread it evenly on a flat plate, obtain a black polymer film after the solvent is volatilized, and completely immerse the black polymer film in an electrolyte solution containing 1 mol/L carbonate solution of lithium hexafluorophosphate (solvent is ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (volume ratio is 1:1:1)), after activation for 6 hours, the porous carbon material composite gel polymer is obtained electrolyte.

Example 2

(1) 100 milliliters of 0.5mol/L sodium citrate ethanol aqueous solutions are mixed with 100 milliliters of 0.5mol/L cobalt nitrate ethanol aqueous solutions, wherein the volume ratio of ethanol and water is 1:1, and then 50 milliliters of 0.1mol are added dropwise /L potassium ferricyanide aqueous solution, stir evenly, put the mixed solution into the reaction kettle, seal it, and perform hydrothermal reaction at 100 °C for 10 hours. to constant weight to obtain a purple solid powder.

(2) After calcining the purple solid powder at a high temperature of 600° C. in a muffle furnace for 5 hours, a black porous structure cobalt oxide iron carbon composite electrode material is obtained.

(3) The black porous structure cobalt oxide iron carbon composite electrode material was completely immersed in 1 mol/L hydrochloric acid aqueous solution for 24 hours, then washed with deionized water, filtered, and dried at 100 °C for 12 hours to obtain a black porous structure carbon material.

(4) Dissolve the black porous structure carbon material and polyvinylidene fluoride-hexafluoropropylene copolymer in N-methylformamide according to the mass ratio of 5:100 (according to the mass ratio of porous structure carbon material and N-methylformamide) 1:10 preparation), stir to obtain a uniform colloid, spread it evenly on a flat plate, obtain a black polymer film after the solvent is volatilized, and completely immerse the black polymer film in an electrolyte solution containing 1 mol/L carbonate solution of lithium hexafluorophosphate (solvent is ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate (volume ratio is 1:1:1)), activated for 6 hours to obtain porous carbon material composite gel polymer electrolyte.

Comparative Example 1

Dissolve polyvinylidene fluoride-hexafluoropropylene copolymer in N-methylformamide (prepared according to the mass ratio of polyvinylidene fluoride-hexafluoropropylene copolymer and N-methylformamide as 10:8), stir to obtain Uniform colloid, uniformly spread it on the flat plate, obtain a white polymer film after the solvent volatilizes, completely immerse the white polymer film in the electrolyte, and the electrolyte is carbonate containing 1mol/L lithium hexafluorophosphate (solvent is Ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate solvent (volume ratio of 1:1:1)), after 6 hours of activation, a gel polymer electrolyte was obtained.

Scanning electron microscope test, liquid absorption rate test, and charge-discharge performance test were performed on the prepared electrode material, and the test results are shown in Figure 1-10.

Liquid Absorption Test: Immerse the weighed polymer membrane (W1) in the liquid electrolyte for 1 hour, then take it out, gently blot the liquid electrolyte on its surface with filter paper, weigh (W2), and the polymer membrane absorbs the liquid electrolyte. The calculation formula of the liquid rate is =(W2-W1)/W1×100%, and each sample film is measured three times in parallel to obtain the average value.

其中：δ为电导率(mS/cm)，d为电解质膜的厚度(cm)，R_b为本体电阻(Ω)，A为电极的面积(cm²)。Conduct conductivity test on the gel polymer electrolyte membrane at room temperature, test its bulk resistance through AC impedance, and obtain its conductivity indirectly, according to the following formula

Where: δ is the electrical conductivity (mS/cm), d is the thickness of the electrolyte membrane (cm), R _b is the bulk resistance (Ω), and A is the area of the electrode (cm ² ).

Battery performance test: Dissolve lithium iron phosphate, polyvinylidene fluoride-hexafluoropropylene, and acetylene black in N-methylpyrrolidone in a mass ratio of 8:1:1 (total solid content mass concentration is 60%), and mechanically stir to form a uniform slurry The material was coated on aluminum foil, heated and dried to make a positive electrode sheet. Lithium was used as the negative electrode, and the gel electrolyte prepared in the example or the electrolyte prepared in the comparative example was used as the separator. In the glove box, a 2032 type button battery was assembled, and set aside for 1 Test after hours.

Table 1 Pore structure data of porous structure carbon materials prepared in Examples 1-2

Table 2 Liquid absorption rate of porous carbon material composite gel polymer electrolytes prepared in Examples 1-2

From the TEM image of Figure 1, it can be seen that the particle size of the porous structure carbon material obtained in Example 1 is about 200 nm, and the surface of the porous structure material is covered with carbon nanotubes, which can provide more pore structures and enable the material to achieve high specific surface area.

It can be seen from the adsorption and desorption curves and pore size distribution curves of the porous structure carbon materials prepared in Examples 1-2 in Figure 2 and Figure 3 that the adsorption and desorption curves of the porous structure carbon materials belong to the type IV isotherm, and have obvious H2 hysteresis loop, indicating that it has a rich mesoporous structure. From the pore structure data of the porous structure carbon materials prepared in Examples 1-2 in Table 1, it can be seen that the specific surface areas of the porous structure carbon materials prepared in Examples 1-2 are 1360.17 and 1119.52 m ² /g, respectively, and the average pore diameters are 5.96 and 4.69nm.

4-6 are scanning electron microscope images of the gel electrolyte membranes prepared in Comparative Example 1 and Examples 1-2. The porous structure carbon material composite gel polymer electrolyte prepared in the examples presents more pores of 5-10 microns, which can accommodate more liquid electrolyte to improve the ionic conductivity of the electrolyte membrane.

Table 2 shows that the liquid absorption rates of the gel electrolyte membranes prepared in Comparative Example 1 and Examples 1 to 2 are 172.17%, 282.76%, and 254.56%, respectively, and the liquid absorption rate of Example 1 is higher than that of Comparative Example 1. 100%. According to the AC impedance test data in Fig. 7, it is calculated that the ionic conductivity of the gel electrolyte membranes prepared in Comparative Example 1 and Examples 1-2 are 1.42×10 ^{-3 S} /cm, 5.63×10 ^-3 S/cm, 5.07×10 ^-3 S/cm, the ionic conductivity of the gel electrolyte membrane after composite porous carbon material is significantly improved.

8 is the galvanostatic charge-discharge curve of the lithium-ion battery assembled with the gel electrolyte membrane prepared in Comparative Example 1 and Examples 1-2 at a current density of 10 mA/g. All batteries can be discharged normally at room temperature. The discharge specific capacity of the positive electrode material lithium iron phosphate is close to that of Example 1. The discharge specific capacity is the largest (146mAh/g), and the comparative example 1 is the smallest (139mAh/g). There is little difference in the performance of different electrolytes during discharge.

FIG. 9 is the discharge performance curves of the lithium ion batteries assembled with the gel electrolyte membranes prepared in Comparative Example 1 and Examples 1-2 at different current densities. With the increase of the discharge current, the gel electrolyte of the composite porous carbon material showed good rate performance, and the cathode material of the lithium ion battery assembled with the porous carbon material composite gel electrolyte membrane prepared in Example 1 under the current density of 200 mA/g The specific capacity is 123mAh/g, which is much higher than the 58mAh/g of Comparative Example 1.

Figure 10 shows the cycle performance curves of the lithium-ion batteries assembled with the gel electrolyte membranes prepared in Comparative Example 1 and Examples 1-2 at a current density of 100 mA/g. The results show that the battery still maintains a high capacity after 1000 times of charge and discharge The retention rate shows that the gel electrolyte membrane prepared in the examples has good stability.

The above-mentioned embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, The simplification should be equivalent replacement manners, which are all included in the protection scope of the present invention.

Claims (10)

1. A preparation method of a porous carbon material composite gel polymer electrolyte is characterized by comprising the following steps:

(1) dissolving sodium citrate and cobalt nitrate in an ethanol water solution, adding a potassium ferricyanide water solution, uniformly stirring, carrying out hydrothermal reaction at 100-120 ℃ for 10-24 hours, centrifuging, washing, and drying to obtain solid powder;

(2) roasting the solid powder at a constant temperature of 500-700 ℃ for 3-6 hours to obtain a porous cobalt oxide iron carbon composite electrode material;

(3) soaking the porous structure cobalt oxide iron carbon composite electrode material in an acid solution, washing, filtering and drying to obtain a porous structure carbon material;

(4) dissolving a porous structure carbon material and a polyvinylidene fluoride-hexafluoropropylene copolymer in an organic solvent, uniformly mixing to obtain a jelly, volatilizing to remove the solvent to obtain a polymer film, and activating the polymer film in an electrolyte to obtain the porous carbon material composite gel polymer electrolyte.

2. The preparation method of the porous carbon material composite gel polymer electrolyte according to claim 1, wherein the molar ratio of the sodium citrate, the cobalt nitrate and the potassium ferricyanide in the aqueous solution of the potassium ferricyanide in the step (1) is (5-10): (3-10): 1;

the mass ratio of the porous structure carbon material to the polyvinylidene fluoride-hexafluoropropylene copolymer in the step (4) is (1-10): 100.

3. the preparation method of the porous carbon material composite gel polymer electrolyte according to claim 2, wherein the mass ratio of the porous structure carbon material in the step (4) to the polyvinylidene fluoride-hexafluoropropylene copolymer is (5-8): 100.

4. the preparation method of the porous carbon material composite gel polymer electrolyte according to claim 1 or 2, wherein the concentrations of the sodium citrate and the cobalt nitrate in the ethanol aqueous solution in the step (1) are both 0.1-0.5 mol/L; the concentration of the potassium ferricyanide aqueous solution is 0.1-0.4 mol/L.

5. The preparation method of the porous carbon material composite gel polymer electrolyte according to claim 4, wherein the soaking time in the step (3) is 12-36 hours; and (4) activating for 2-10 h.

6. The preparation method of the porous carbon material composite gel polymer electrolyte according to claim 4, wherein the volume ratio of ethanol to water in the ethanol aqueous solution in the step (1) is 1: (1-5); the acid solution in the step (3) is a hydrochloric acid aqueous solution with the concentration of 1-4 mol/L; the mass ratio of the porous structure carbon material to the organic solvent in the step (4) is 1: (5-20); and (4) the electrolyte is a carbonate solution containing 1-1.2 mol/L lithium hexafluorophosphate.

7. The preparation method of the porous carbon material composite gel polymer electrolyte according to claim 4, wherein the hydrothermal reaction time in the step (1) is 10-12 h; roasting in the step (2) at the temperature of 600-700 ℃ for 5-6 h; and (4) the solvent of the electrolyte in the step (4) is a solvent with the volume ratio of 1: 1: 1 of a mixed solvent of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate.

8. The preparation method of the porous carbon material composite gel polymer electrolyte according to claim 4, wherein the drying temperature in the step (1) is 80-120 ℃, and the drying is carried out to constant weight; washing liquid used for centrifugal washing is water, and washing is carried out for 1-5 times;

completely soaking the porous structure cobalt oxide iron carbon composite electrode material in an acid solution; the washing liquid used for washing is water, the drying temperature is 80-120 ℃, and the drying time is 6-24 hours;

the organic solvent in the step (4) is N-N methylformamide; the polymer film is completely immersed in the electrolyte.

9. A porous carbon material composite gel polymer electrolyte prepared by the method of any one of claims 1 to 8.

10. Use of a porous carbon material composite gel polymer electrolyte according to claim 9 in the field of batteries.

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