Method for modifying carbon fluoride by combining mussels-biomimetic PPy-PDA coating and in-situ reduction of silver nanoparticles under ultraviolet

Abstract

The application discloses a method for modifying fluorocarbon by combining mussel-biomimetic PPy-PDA coating and in-situ reduction of silver nanoparticles under ultraviolet light, and belongs to the fields of fluorocarbon material modification and primary battery technology. In the method, a high-conductivity and high-adhesion polypyrrole-polydopamine (PPy-PDA) coating layer is first in-situ polymerized on fluorocarbon to form a mussel-biomimetic PPy-PDA coating layer, and then, the surface of the fluorocarbon modified by in-situ growth of Ag NPs is reduced by ultraviolet photoelectrons to form a composite nanostructure and to regulate the intrinsic conductivity of the fluorocarbon material. The use of the PPy-PDA layer to coat the fluorocarbon can effectively improve the binding force between the fluorocarbon and the silver nanoparticles, reduce the damage of the alkaline silver ammine solution to the fluorocarbon, and hinder the damage of photoelectrons to the C-F bond of the fluorocarbon itself. The silver nanoparticles coated on the surface of the fluorocarbon can effectively reduce the voltage delay in the initial stage of discharge and slow down the electrochemical polarization, thereby improving the rate performance of the lithium / fluorocarbon battery without affecting the specific capacity. Therefore, the lithium primary battery prepared by the combined modification method of the fluorocarbon material has the characteristics of high energy density and high rate performance, and lays a foundation for the popularization and application of the lithium / fluorocarbon battery in high-power discharge occasions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of new materials and lithium primary batteries, and particularly relates to a combined modification method of carbon fluoride material. BACKGROUND

[0002] A lithium primary battery is composed of a positive electrode of carbon fluoride material (CF x ) and a negative electrode of metal lithium. x ) battery, a lithium / sulfur dioxide battery, a lithium / thionyl chloride battery, and a lithium / carbon fluoride battery. The lithium / carbon fluoride battery has the highest theoretical energy density (2180 Wh / kg) and a practical specific energy of 250-800 Wh / kg compared to other solid material positive electrode batteries. Meanwhile, the Li / CF x battery has the following advantages: (1) wide working temperature range: the carbon fluoride material is stable and can be used in a wide temperature range of-20-80℃; (2) stable working voltage: the active material usage rate of the carbon fluoride in the positive electrode can reach almost 100% after the reaction, and the working voltage is basically stable until the end of discharge; (3) low self-discharge rate: the self-discharge rate of the lithium / carbon fluoride battery is very low (annual self-discharge rate <1%), so it has an ultra-long storage life of more than ten years. At present, the lithium / carbon fluoride battery has been widely used in aerospace, deep sea exploration, military, medical treatment and other fields, and has a very broad development prospect. However, the current carbon fluoride material still has some problems. The poor intrinsic conductivity of carbon fluoride and the strong covalent C-F bond energy cause serious polarization at the initial stage of discharge of the lithium / carbon fluoride battery, and the voltage hysteresis is serious, the high-rate discharge capacity attenuation is large, about 30% of the theoretical capacity, which limits the deeper development and utilization of the lithium / carbon fluoride primary battery. In order to make up for the voltage hysteresis and poor rate performance of the lithium / carbon fluoride battery, Chinese patent 201911130266.7 discloses a preparation method of a V2O5-carbon fluoride composite positive electrode material, which uses the high voltage platform and good rate performance of V2O5 material to make up for the poor rate performance of the lithium / carbon fluoride battery, but the voltage hysteresis effect still exists. SUMMARY

[0003] The present application aims at the defects existing in the background art, and provides a method for modifying PPy-PDA coated carbon fluoride by ultraviolet irradiation reduction of silver nanoparticles. The present application coats the surface of carbon fluoride with PPy-PDA by using the adhesion and conductivity of PPy-PDA, modifies the surface of carbon fluoride material by ultraviolet irradiation, and in-situ composites silver nanoparticles by using photo-induced technology, so as to obtain a composite positive electrode material with high rate performance, which is applied to lithium primary batteries, effectively improves the specific capacity of the battery, and improves the phenomenon of voltage hysteresis in the initial stage of discharge.

[0004] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0005] A method for modifying PPy-PDA coated carbon fluoride by ultraviolet irradiation reduction of silver nanoparticles, characterized in that it comprises the following steps:

[0006] Step 1: 0.2-2 mL of pyrrole (C4H5N) and 0.05-0.5 g of dopamine hydrochloride (C8H 12 ClNO2) are added to 25-250 mL of Tris buffer, and 25-250 mL / 0.2 g·mL -1 of CF x / EG suspension is added and stirred uniformly, then 5-50 mL of 0.01 M APS-Tris solution is slowly added to the above mixture, and the reaction is carried out at 8℃ for 18 h.

[0007] Step 2: the PPy-PDA coated CF x is centrifuged and freeze-dried, and is placed in 100 mL of a mixture of ethylene glycol (EG) and ethanol (C2H5OH) (ratio 3:1) and stirred uniformly, and a silver ammonia solution (Ag(NH3)2OH) with a concentration of 0.02-0.2 mol·L -1 is prepared by using silver nitrate (AgNO3) and ammonia water (NH3·H2O).

[0008] Step 3: 50-300 mL of silver ammonia solution is added to the CF x solution obtained in step 2, and is irradiated under a UV lamp with a wavelength of 365-395 nm for 2-96 h, and the CF x material with ultraviolet irradiation reduced Ag NPs is centrifuged and freeze-dried to obtain a carbon fluoride composite positive electrode material.

[0009] Further, the content of pyrrole in step 1 is 0.05 g, 0.1 g, 0.2 g or 0.4 g.

[0010] Further, the pyrrole and dopamine hydrochloride in step 1 can be other good conductive and adhesive coating layers.

[0011] Further, the dopamine hydrochloride in step 1 has a content of 0.2 mL, 0.4 mL, 0.8 mL, 1.6 mL.

[0012] Further, the silver ammine solution in step 2 has a concentration of 0.02 mol / L, 0.04 mol / L, 0.8 mol / L, 0.16 mol / L.

[0013] Further, the solution in step 2 can be a solution of any solvent containing silver ions, not limited to the silver ammine solution.

[0014] Further, the solution in step 2 can be a solution of other metal ions.

[0015] Further, the light source for photoinduction in step 3 can be any one of ultraviolet light, infrared light, visible light, white light, blue light and other common light induction technology light and combinations thereof.

[0016] Further, the ultraviolet irradiation time in step 2 is 12 h, 24 h, 48 h, 96 h.

[0017] The application also provides an application of the above-mentioned ultraviolet irradiation reduced silver nanoparticle modified PPy-PDA coated carbon fluoride as a positive electrode material of a lithium / carbon fluoride primary battery, which comprises a carbon fluoride positive electrode, a lithium metal negative electrode, an electrolyte and a separator.

[0018] Compared with the prior art, the application has the following beneficial effects:

[0019] The application uses ultraviolet irradiation reduced silver nanoparticle modified PPy-PDA coated carbon fluoride: first, using a PPy-PDA layer to coat carbon fluoride can effectively improve the bonding force between carbon fluoride and silver nanoparticles, reduce the damage of the alkaline silver ammine solution to carbon fluoride, hinder the destruction of the C-F bond of carbon fluoride itself by photoelectrons, realize in-situ growth of silver nanoparticles on the surface of carbon fluoride by ultraviolet irradiation light reduction of the silver ammine solution without affecting the energy density, form a composite material, and use it as a positive electrode material of a lithium / carbon fluoride primary battery. The silver nanoparticles compounded on the surface of carbon fluoride can effectively improve the conductivity of carbon fluoride, slow down the electrochemical polarization in the discharge process of the primary battery, and at the same time reduce the voltage hysteresis effect in the initial stage of discharge, thereby improving the rate performance of the lithium / carbon fluoride battery. Therefore, based on the ultraviolet irradiation reduced silver nanoparticle modification technology, the modified carbon fluoride has good rate performance and no obvious voltage hysteresis effect, which is of great significance for improving the performance of lithium / carbon fluoride batteries and promoting their application and popularization. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is an experimental flowchart for the implementation case.

[0021] Figure 2 SEM images of commercial fluorocarbon raw material, modified fluorocarbon material obtained in Example 2; wherein (a) is the SEM image of commercial fluorocarbon raw material; (b) is the SEM image of modified fluorocarbon material obtained in Example 2;

[0022] Figure 3 TEM images of modified fluorocarbon material obtained in Example 2 at different scales;

[0023] Figure 4 XRD images of commercial fluorocarbon raw material, modified fluorocarbon material obtained in Example 1, Example 2

[0024] Figure 5 Discharge curves of batteries assembled with commercial fluorocarbon raw material as positive electrode material at different discharge rates;

[0025] Figure 6 Discharge curves of batteries assembled with modified fluorocarbon material obtained in Example 1 as positive electrode material at different discharge rates;

[0026] Figure 7 Discharge curves of batteries assembled with modified fluorocarbon material obtained in Example 2 as positive electrode material at different discharge rates;

[0027] Figure 8 EIS curves of batteries assembled with commercial fluorocarbon raw material and modified fluorocarbon material obtained in Example 1, Example 2 as positive electrode material. DETAILED DESCRIPTION

[0028] The technical solutions of the present application will be described in detail below with reference to the accompanying drawings and examples, and the example flow chart is shown in Figure 1

[0029] Example 1

[0030] A method for modifying fluorocarbon by ultraviolet irradiation reduction of silver nanoparticles, characterized in that it comprises the following steps:

[0031] 0.2-2 mL of pyrrole (C4H5N) and 0.05-0.5 g of dopamine hydrochloride (C8H 12 ClNO2) are added to 25-250 mL of Tris buffer, and 25-250 mL / 0.2 g·mL -1 of CF x / EG suspension is added and stirred uniformly, then 5-50 mL of 0.01 M APS-Tris solution is slowly added to the above mixture, and the reaction is carried out at 8°C for 18 h (Example 1: PP).

[0032] Example 2

[0033] ​The example 1 was added into 50-300 mL of silver amide solution and irradiated under UV light with wavelength of 365-395 nm for 2-96 h. The Ag NPs composite CF was obtained by UV irradiation reduction x The carbon fluoride composite positive electrode material (PPU12-3) was obtained after centrifugation and freeze-drying of the material.

[0034] Figure 2 and Figure 3 The SEM and TEM images of the commercial carbon fluoride raw material and the modified carbon fluoride material obtained in example 2 are shown in the figure. As can be seen from the figure, the commercial carbon fluoride raw material is irregular spherical structure at nanometer level, and the modified carbon fluoride material obtained in example 2 has fine Ag nanoparticles on the surface.

[0035] Figure 4 The XRD patterns of the commercial carbon fluoride raw material, the modified carbon fluoride obtained in example 1 and example 2 are shown in the figure. Figure 4 The figure shows obvious silver characteristic peaks.

[0036] Battery assembly:

[0037] The commercial carbon fluoride raw material, the modified carbon fluoride material obtained in examples 1-3, conductive additive (SP) and binder (PVDF) were prepared into slurry in a mass ratio of 8:1:1. The slurry was uniformly coated on the current collector aluminum foil and dried in a vacuum drying oven at 80°C for 12 h to obtain positive electrode sheet; the metal lithium was used as negative electrode, and the carbon fluoride electrode sheet was used as positive electrode to assemble a button cell in a glove box, and then the button cell was placed for 24 h for waiting for electrochemical performance test.

[0038] Figure 5 The discharge curves of the battery assembled with the commercial carbon fluoride raw material as positive electrode material at different discharge rates are shown in the figure. As can be seen from the figure, Figure 5 It can be seen that the rate performance of the commercial carbon fluoride raw material is poor, and there is a serious voltage hysteresis effect in the initial stage of discharge, and the carbon fluoride raw material cannot be discharged at a current density of more than 5 A / g.

[0039] Figure 6 The discharge curves of the battery assembled with the modified carbon fluoride material obtained in example 1 as positive electrode material at different discharge rates are shown in the figure. As can be seen from the figure, the voltage hysteresis effect of the modified carbon fluoride material in the initial stage of discharge is obviously improved, and the rate performance is increased.

[0040] Figure 7 The discharge curves of the battery assembled with the modified carbon fluoride material obtained in example 2 as positive electrode material at different discharge rates are shown in the figure. As can be seen from the figure, the voltage hysteresis effect of the modified carbon fluoride material in the initial stage of discharge is obviously improved, the capacity density is increased at large current density, and the specific capacity of 602.10 mAh / g can be reached at a current density of 15 A / g.

[0041] Figure 8 EIS curves of the batteries assembled with the commercial carbon fluoride raw material and the modified carbon fluoride materials of Example 1 and Example 2 as the positive electrode material; Figure 8 In the middle and high frequency part, the semicircle diameter is the charge transfer resistance of the battery, and the slope of the straight line in the low frequency part is related to the diffusion rate of lithium ions. From Figure 8 It can be seen that the charge transfer resistance of the modified carbon fluoride is significantly reduced.

Claims

1. A method for modifying fluorocarbon by combining the mussel-inspired PPy-PDA coating and in-situ reduction of silver nanoparticles under UV, characterized in that, The method comprises the following steps: Step 1, 0.2~2 mL pyrrole and 0.05~0.5 g dopamine hydrochloride are added to 25~250 mL Tris buffer, and 25~250 mL / 0.2 g·mL -1 of CF x / EG suspension is stirred uniformly, then 5~50 mL of 0.01 M APS-Tris solution is slowly added to the above mixture, and the reaction is carried out at 8 ℃ for 18 h; Step 2, the PPy-PDA coated CF x is centrifuged, freeze-dried, and placed in 100 mL of a mixture of ethylene glycol (EG) and ethanol with a ratio of 3:1 and stirred uniformly, and a silver ammonia solution with a concentration of 0.02~0.2 mol·L -1 is prepared using silver nitrate and ammonia; Step 3, the mixed solution obtained in Step 2 is added to 50~300 mL of silver ammonia solution and irradiated under a 365~395 nm wavelength ultraviolet lamp for 2~96 h, and the ultraviolet irradiation reduced Ag nanoparticle composite CF x material is centrifuged and freeze-dried to obtain a fluorocarbon composite positive electrode material.

2. The method for modifying carbon fluoride by combining perna mussel-biomimetic PPy-PDA coating and in-situ reduction of silver nanoparticles under UV according to claim 1, characterized in that, The pyrrole and dopamine hydrochloride in step 1 are converted into polypyrrole (PPy) and polydopamine (PDA) during the reaction, which provide a good conductive and adhesive coating layer for the carbon fluoride.

3. The method for modifying carbon fluoride by combining perna mussel-biomimetic PPy-PDA coating and in-situ reduction of silver nanoparticles under UV according to claim 1, characterized in that, The concentration of the silver ammine solution in step 2 is 0.02 mol / L, 0.04 mol / L, 0.08 mol / L or 0.16 mol / L.

4. The method for modifying carbon fluoride by combining perna mussel-biomimetic PPy-PDA coating and in-situ reduction of silver nanoparticles under UV according to claim 1, characterized in that, The time for the ultraviolet irradiation to reduce silver ions in step 3 is 2-96 hours.

5. The modified carbon fluoride obtained by the method in any one of claims 1-4 is used as a positive electrode material of a lithium / carbon fluoride primary battery.

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