CN106229464B - Conductive polymer film and positive pole piece modified by conductive polymer film - Google Patents
Conductive polymer film and positive pole piece modified by conductive polymer film Download PDFInfo
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- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/137—Electrodes based on electro-active polymers
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- H—ELECTRICITY
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- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/60—Selection of substances as active materials, active masses, active liquids of organic compounds
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- H—ELECTRICITY
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
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Abstract
The invention discloses a conductive polymer film and a positive pole piece modified by the conductive polymer film, wherein the conductive polymer film is prepared by a method comprising the following steps: 1) coating an initiator on a film-forming substrate, and placing the film-forming substrate coated with the initiator in a closed container containing a conductive polymer monomer; 2) controlling the vacuum condition of the closed container to evaporate the conductive polymer monomer, carrying out in-situ polymerization on the film-forming substrate coated with the initiator to form a film, and drying to obtain the conductive polymer. The conductive polymer film is prepared by adopting a vacuum evaporation coating process, so that the conductive polymer film with uniform thickness can be formed without complicated and harsh condition control in the polymerization process; the obtained conductive polymer has uniform thickness, can be placed between the positive electrode and the diaphragm, inhibits side reaction between an electrode material and electrolyte, and improves the structural stability and the thermal stability of the positive electrode material in the charge and discharge processes of the battery, thereby improving the electrochemical performance of the material.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a conductive polymer film and a positive pole piece modified by the conductive polymer film.
Background
The lithium ion battery has the outstanding advantages of high specific energy, large capacity, high voltage, small self-discharge, good cyclicity, light weight, small volume, long service life and the like, and is an ideal power supply for portable electronic equipment such as mobile phones, notebook computers and the like. In recent years, in order to protect the environment and realize sustainable development, countries around the world compete for the development of the electric automobile industry, so as to finally and completely replace the traditional fuel automobile. The key for restricting the development of the electric automobile industry is to develop a power battery with excellent performance. The positive electrode material is particularly urgent and critical to meet the requirements of power batteries on energy density, safety, price, service life and the like.
In recent years, LiFePO with high specific capacity4(170mAh/g), ternary Material (c)<180mAh/g) and lithium-rich layered cathode material (b)>200mAh/g) and a novel sulfur positive electrode>1675mAh/g) and the like, and is considered as the positive electrode material of the power lithium ion battery with the most development prospect. LiFePO4The medium iron source has the advantages of rich reserves, environmental friendliness, excellent cycle stability and the like; ternary material incorporating LiCoO2、LiNiO2And LiMnO2The advantages of the three materials are brought into play, the synergistic effect of the three materials is exerted, and the cost is relatively low; lithium-rich cathode material Li with layered structure1+xA1-xO2The (A is the combination of various metal atoms such as Ti, Cr, Fe, Co, Ni, Mn and the like) and the novel active sulfur positive electrode material have higher theoretical specific capacity, and are most hopeful to become the positive electrode material for developing the high-energy density (more than 300Wh/kg) lithium ion battery.
Although the lithium ion battery anode material has many advantages, there are many problems in the actual charge and discharge process, and the following have significant influence on the battery performance: (1) part of the positive electrode material has poor conductivity; (2) some components in the electrolyte can generate side reaction with the anode material, the normal structure of the material is damaged, and the by-product has adverse effect on the structure, the conductivity and the migration of lithium ions of the electrode; (3) during the charging and discharging process, part of the positive electrode material expands and contracts in a reaction manner, so that the whole structure of the electrode is damaged and the conductivity is deteriorated.
Currently, from the research progress, the main means for overcoming the above problems of the positive electrode material are doping (transition metal ions, rare earth elements, etc.) and coating (metal oxides, graphene, nanocarbon, etc.). The above methods all solve the problems from the perspective of battery material synthesis, have the disadvantages of complex process, high cost, large difficulty in large-scale production, difficult achievement transformation and the like, and are mostly adopted in experimental research at present.
The conductive polymer is a polymer material with special electrical, optical and electrochemical properties due to a conjugated pi-electron system, has more researches on the aspects of improving the rate capability and the cycling stability of a low-conductivity material in recent years, and is a feasible method for improving the electrochemical performance of a positive electrode material and the performance of a lithium ion battery.
In the prior art, a solution in-situ polymerization method is usually adopted for modifying a positive electrode material by using a conductive polymer, and the method mainly comprises the steps of dispersing a polymer monomer, an initiator and a coated material in a solvent, and carrying out in-situ polymerization to obtain the material coated by the conductive polymer. The solution in-situ polymerization process mainly has the following disadvantages: 1. in the in-situ polymerization process, a polymer monomer, an initiator and a coated material coexist in a solution, and because the concentration of the monomer is high, the polymerization initiating speed is extremely high, and the polymerization is not uniform, the thickness of a conductive polymer coating layer on the surface of a finally formed material is different, and the electrochemical performance of the material is influenced; in order to overcome the problems, harsh conditions are needed during coating, such as strictly controlling the temperature of the system to be below 0 ℃, strongly stirring and the like, the reaction conditions are difficult to control, and industrial production is not easy to realize; 2. in general, solution in-situ polymerization is to coat a lithium ion battery anode material, then prepare slurry and coat the slurry on a current collector, because the size and the property of the anode material can be changed to a certain extent after the coating of a conductive polymer, when the solution is applied and actually produced, the original coating process must be adjusted, and the original processes such as the proportion and the dispersion condition of slurry mixing raw materials, the coating condition, the drying condition, the sheet making process and the like are not suitable for the coated anode material any more; 3. the solution in-situ polymerization coating is to coat the anode material powder particles, and the coated particles are easy to cause the damage of a coating layer in the subsequent pulping coating process; meanwhile, the conductive polymer has poor conductivity relative to a carbon conductive material, so that after the particles are coated, the conductive contact among the particles is poor, and the resistance of the formed pole piece is increased inevitably. Due to the existence of the problems, the conventional conductive polymer modified positive electrode material and the conventional positive electrode plate have complex preparation procedures and poor electrochemical performance, and the development of the conductive polymer modified positive electrode material is limited.
Disclosure of Invention
The invention aims to provide a conductive polymer film, which solves the problems of complex preparation process and poor electrochemical performance of a positive pole piece modified by a conductive polymer.
The second purpose of the invention is to provide a positive pole piece modified by the conductive polymer film.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a conductive polymer film prepared by a process comprising the steps of:
1) coating an initiator on a film-forming substrate, and placing the film-forming substrate coated with the initiator in a closed container containing a conductive polymer monomer;
2) controlling the vacuum condition of the closed container to evaporate the conductive polymer monomer, carrying out in-situ polymerization on the film-forming substrate coated with the initiator to form a film, and drying to obtain the conductive polymer.
In the step 1), the conductive polymer monomer is pyrrole, thiophene or aniline. The conductive polymer monomer is in a liquid state at normal temperature and normal pressure.
The conductive polymer in the conductive polymer film is one of polypyrrole (PPy), polythiophene (PTh), Polyaniline (PAN) and a derivative thereof, namely poly (N-hydroxyethylaniline).
In the step 1), the initiator is an oxidant solution, and the oxidant solution contains an oxidant with the concentration of 0.1-1.0 mol/L.
The oxidant is (NH)4)2S2O8、(NH4)2Ce(NO3)6、K2Cr2O7、Ce(SO4)2.2(NH4)2SO4、FeCl3、KMnO4、H2O2Any one or combination thereof.
The oxidant solution also contains protonic acid with the concentration of 0.07-0.3 mol/L. Proton(s)The acid can provide the pH value required by the reaction system and the H required by proton exchange+。
The protonic acid includes inorganic protonic acid and organic protonic acid. The inorganic protonic acid comprises H2SO4、HCl、HNO3、H3PO4、HCO3-、NH4+. The organic protonic acid comprises CH3COOH, sulfonic acid group compound, benzene phosphoric acid, benzoic acid and the derivative salicylic acid thereof.
The protonic acid is H2SO4、HCl、HNO3、H3PO4、HCO3-、NH4+、CH3COOH, sulfonic acid group compound, benzene phosphoric acid, benzoic acid and any one of salicylic acid derivatives thereof.
The sulfonic compound is camphorsulfonic acid (CSA) or dodecylbenzenesulfonic acid (DBSA).
The solvent used by the oxidant solution is any one or a mixture of two of water, ethanol, acetonitrile, tetrahydrofuran, chloroform, N-methyl pyrrolidone and m-cresol.
When the solvent is a mixture of two organic solvents, the volume ratio of the two organic solvents is 1-3: 1-3.
In the step 2), the vacuum condition is as follows: the vacuum degree is 0.001-0.09 MPa. The vacuum degree of the closed container can be controlled by controlling the amount of the inert gas. The inert gas is nitrogen or argon.
In the step 2), the temperature of the in-situ polymerization is 20-60 ℃. The temperature is provided by a water bath device; the water bath device is a constant temperature water bath. The temperature can be determined according to the volatilization temperature and the polymerization temperature of different conductive polymer monomers.
In the step 2), the time of in-situ polymerization is 0.1-70 h. Preferably, the time of in-situ polymerization is 1-24 h. Further preferably, the time of in-situ polymerization is 10-18 h.
The positive pole piece comprises a positive plate formed by a current collector and a positive material layer attached to one side or two sides of the current collector, wherein the conductive polymer film is further attached to the outer side of the positive material layer on the positive plate.
The positive pole piece is prepared by the method comprising the following steps:
a) taking a positive plate, coating an initiator on the surface of a positive material layer of the positive plate, and placing the positive plate coated with the initiator in a closed container filled with a conductive polymer monomer;
b) controlling the vacuum condition of the closed container to evaporate the conductive polymer monomer, carrying out in-situ polymerization on the positive plate coated with the initiator to form a film, and drying to obtain the conductive polymer film.
The positive plate is prepared by the following method: and uniformly mixing the positive active substance, the conductive agent and the binder to prepare slurry, uniformly coating the slurry on a current collector, and drying to obtain the lithium ion battery.
The positive active material is polyanionic olivine type LiFePO4、LiFePO4/C cathode material (carbon-coated LiFePO)4Positive electrode material), LiMn2O4Or an S/C composite positive electrode material (sulfur-carbon composite positive electrode material).
The current collector is an aluminum foil.
In the step b), the positive plate after in-situ polymerization film forming is washed before drying; and the washing is to immerse the positive plate into water or an organic solvent for 1-60 s for washing, or to wash with any one of water, ethanol, acetone and chloroform. The purpose of washing is to remove impurity metal ions introduced on the conductive polymer film and to restore acid-base neutrality of the positive plate, so as to play a role in activating and protecting the final material.
In the step b), the drying is carried out for 8-36 h under the condition of 60 ℃ in vacuum.
A lithium ion battery comprises a positive electrode, a negative electrode and a diaphragm, wherein the positive electrode adopts the positive pole piece.
The conductive polymer film of the invention has the appearance of particles and the interior of a network structure. The particle size of the particles is 1-200 nm. Preferably, the particle size of the particles is 20-100 nm. The thickness of the conductive polymer film is 10-500 nm.
The conductive polymer in the conductive polymer film is present in the form of a single or multi-layered conductive carbon structure. The conductive polymer film is coated on the surface of the anode material layer and positioned between the anode active material and the electrolyte, thereby playing the role of a buffer layer and the role of conductivity, increasing the electron transmission capability and promoting the diffusion of lithium ions.
The conductive polymer film is prepared by coating an initiator on a film-forming substrate, evaporating a conductive polymer monomer by adopting a vacuum evaporation coating process, and carrying out in-situ polymerization on the film-forming substrate coated with the initiator, wherein in the vacuum evaporation coating process, the monomer and the initiator are separated, and the monomer vapor contacts with the initiator on the film-forming substrate to initiate polymerization, so that the polymerization speed is controlled by the diffusion of the monomer vapor, and meanwhile, the monomer vapor has low concentration relative to liquid and is more uniformly contacted with the film-forming substrate and the initiator, so that the conductive polymer film with uniform thickness can be formed without complicated and harsh condition control in the polymerization process; the obtained conductive polymer has uniform thickness, can be placed between the positive electrode and the diaphragm, inhibits side reaction between an electrode material and electrolyte, and improves the structural stability and the thermal stability of the positive electrode material in the charge and discharge processes of the battery, thereby improving the electrochemical performance of the material.
According to the positive pole piece, the conductive polymer film is attached to the outer side of the positive pole material layer on the positive pole plate, the thickness of the conductive polymer film is uniform, a coating is formed on the surface of the positive pole material layer, and the conductive polymer film is located between the positive pole material layer and the diaphragm during working, so that the side reaction between an electrode material and an electrolyte can be inhibited, the structural stability and the thermal stability of the positive pole material in the charging and discharging processes of the battery are improved, and the electrochemical performance of the material is improved.
The preparation method of the positive pole piece comprises the steps of coating the initiator on the surface of the positive pole material layer of the positive pole plate, evaporating the conductive polymer monomer by adopting a vacuum evaporation coating process, and polymerizing the conductive polymer monomer in situ on the surface of the positive pole material layer of the positive pole plate coated with the initiator to form the conductive polymer film, wherein compared with the existing solution in situ polymerization method, the preparation method has the following obvious advantages:
1. in the preparation method, the monomer and the initiator are separated, and the polymerization is initiated only when the monomer vapor contacts the initiator on the film forming substrate, so that the polymerization speed is controlled by the diffusion of the monomer vapor, and meanwhile, the monomer vapor has low concentration relative to the liquid and is more uniformly contacted with the film forming substrate and the initiator, so that a conductive polymer film with uniform thickness can be formed without complicated and harsh condition control in the polymerization process;
2. the preparation method is that the initiator is coated on the formed positive plate and contacts with monomer steam to initiate polymerization, and the preparation method can be directly applied to the production line of the original positive plate, and the original process of coating the positive plate to form the positive material layer, namely the preparation process of the original positive plate, does not need to be adjusted;
3. the preparation method is to form a layer of uniform conductive polymer film on the surface of the positive electrode material layer of the formed positive electrode plate, and coat the positive electrode material layer on the positive electrode plate, so that the impedance of the positive electrode plate is not increased obviously while the electrode structure is stabilized and the electrochemical performance is improved.
4. The preparation method solves the problems of low conductivity, low specific capacity, poor cycle performance and rate capability and low coulombic efficiency of the cathode material serving as an important bottleneck for inhibiting the development of the lithium ion battery, has simple and easy process, does not need a template, is convenient to operate, has easily controlled conditions and high practicability, and is suitable for large-scale industrial production.
When the conductive polymer film is prepared, the volatility of the liquid polymer monomer is closely related to the temperature and the pressure of a system, the vacuum degree of a thermometer of the system is controlled, and the vapor pressure of the liquid polymer monomer can be adjusted. The steam of the polymer monomer contacts with the formed positive plate coated with the initiator in advance to initiate in-situ polymerization, and the formed conductive polymer film forms a coating layer for the positive electrode material layer. The final thickness of the conductive polymer film (coating layer) is regulated and controlled by controlling the polymerization time and the vacuum degree of a thermometer. The vacuum degree and the heat source provided by the invention enable the liquid monomer of the conductive polymer at the bottom of the container to be evaporated to form monomer vapor with certain concentration, the vapor contacts with an initiator (oxidant or mixture of the oxidant and protonic acid) on the positive plate to react, and the in-situ polymer is formed into a conductive polymer film.
Drawings
FIG. 1 is a schematic view showing the structure of a vacuum evaporation coating apparatus according to example 1;
FIG. 2 shows a single-side modified pure LiFePO of the conductive polymer film obtained in example 14Positive plate and unmodified pure LiFePO4Comparing the charge and discharge of the button cell of the positive plate;
FIG. 3 shows a single-sided modified pure LiFePO of the conductive polymer film obtained in example 14Positive plate and unmodified pure LiFePO4Comparative graph of cycling performance of button cell of positive plate;
FIG. 4 shows the pure LiFePO with double-sided modification of the conductive polymer film obtained in example 24Positive plate and unmodified pure LiFePO4Comparing charge and discharge of the positive plate;
FIG. 5 shows the pure LiFePO with double-sided modification of the conductive polymer film obtained in example 24Positive plate and unmodified pure LiFePO4Comparison of cycle performance for positive plate;
FIG. 6 is a comparative graph of charge and discharge of the single-sided modified S/C positive electrode plate and the unmodified S/C positive electrode plate of the conductive polymer film obtained in example 3;
FIG. 7 is a comparison graph of charge and discharge of the single-sided modified S/C positive electrode plate and the unmodified S/C positive electrode plate of the conductive polymer film obtained in example 3.
Detailed Description
The present invention will be further described with reference to the following embodiments.
Example 1
The positive pole piece of this embodiment includes the positive plate that is formed by the mass flow body and the positive electrode material layer that adheres to current collector one side, still adhere to the conducting polymer membrane on the positive plate outside positive electrode material layer.
The preparation method of the positive pole piece of the embodiment comprises the following steps:
a) preparing a positive plate: pure LiFePO in olivine form4Is prepared from positive electrode active substance, acetylene black as conductive agent, and polytetrafluoroethylene as binder by mixing at a mass ratio of 80:10:10, adding appropriate amount of NMP as solvent to obtain slurry, and coating the slurry on one side of aluminum foil (with a current collector thickness of 0.02mm)Coating the surface of the positive plate with a coating thickness of 0.02mm, and vacuum-drying at 120 ℃ for 12h to form a positive material layer on the aluminum foil to obtain the positive plate;
b) uniformly coating a layer of initiator on the surface of the positive electrode material layer of the positive electrode plate obtained in the step a), wherein the initiator contains (NH) with the concentration of 0.4mol/L4)2S2O8And 0.1mol/L of (NH)4)2Ce(NO3)6And a solution of HCl with a concentration of 0.5mol/L (the solvent is a mixed solvent with a volume ratio of water to ethanol of 9: 1);
in the vacuum evaporation coating apparatus of the present embodiment, as shown in fig. 1, a closed container 2 is horizontally placed in a constant temperature water bath 1, and a thermometer 9 for reading the temperature of the water bath is placed in the constant temperature water bath 1; the closed container 2 is connected with a vent pipeline 7 for introducing inert gas and an air extraction pipeline 8 for vacuumizing, a vent valve 10 is arranged on the vent pipeline, and an air extraction valve 11 is arranged on the air extraction pipeline and used for controlling the vacuum degree of the closed container; an excessive conductive polymer monomer 3 (aniline monomer in the embodiment) is placed at the bottom in the closed container 2, and a bracket 6 for placing a positive plate is also placed in the closed container 2; when in use, the positive plate 4 coated with the initiator is placed on the bracket 6 in the closed container 2, and the positive plate 4 is not in contact with the liquid conductive polymer monomer 3;
c) controlling the temperature of the constant temperature water bath at 60 deg.C and the vacuum degree in the sealed container at 0.08MPa to evaporate aniline monomer at the bottom of the sealed container to form aniline vapor with a certain concentration in the sealed container, wherein the aniline vapor and oxidant (NH) on the positive plate4)2S2O8And (NH)4)2Ce(NO3)6Contacting with protonic acid HCl to perform proton exchange and in-situ polymerization, forming a conductive polyaniline film 5 (shown in figure 1) with the thickness of 100nm on the surface of the positive electrode material layer of the positive plate after 24h, taking out the positive plate, washing the surface with water, and performing vacuum drying at 80 ℃ for 24h to obtain the single-side modified LiFePO of the conductive polymer film4And a positive plate.
The single surface of the conductive polymer film is modified with LiFePO4Cutting the positive plate into a wafer with a diameter of 1.4cm, and pressingA sheet as a positive electrode; and (3) adding a proper amount of electrolyte into a metal lithium sheet serving as a cathode and Celgard2400 serving as a diaphragm, and assembling the battery in a glove box. The battery is subjected to charge-discharge and cycle performance tests in a LAND battery test system, the results are shown in figures 2 and 3, the charge-discharge cut-off voltage is 2.7-4.2V, the discharge specific capacity of the obtained battery is greatly improved compared with that of an unmodified material, the voltage of a charge-discharge platform is improved from 3.3V to 3.4V and is stable, and the cycle performance is obviously improved.
Example 2
The positive pole piece of this embodiment includes the positive plate that is formed by the mass flow body and the positive electrode material layer that adheres to the mass flow body both sides, still adhere to the conducting polymer membrane on the positive plate outside positive electrode material layer.
The preparation method of the positive pole piece of the embodiment comprises the following steps:
a) preparing a positive plate: pure LiFePO in olivine form4Uniformly mixing a positive active substance, acetylene black as a conductive agent and polyvinylidene fluoride as a binder according to the mass ratio of 89:7:4, preparing slurry by taking NMP as a solvent, uniformly coating the slurry on the front and back surfaces of an aluminum foil (the thickness of a current collector is 0.02mm) by using a coating machine, wherein the coating thickness is 0.02mm, and performing vacuum drying at 120 ℃ for 12 hours to form positive material layers on the front and back surfaces of the aluminum foil to obtain a positive plate;
b) dividing the positive plate obtained in the step a), and uniformly coating an initiator on the surface of the positive material layer, wherein the initiator is (NH) with the concentration of 0.6mol/L4)2S2O8And a solution of HCl with a concentration of 0.5mol/L (the solvent is a mixed solvent with a volume ratio of water to ethanol of 7: 3);
in the vacuum evaporation coating device of the embodiment, like the embodiment 1, the positive plate coated with the initiator is placed in a closed container, the closed container is horizontally placed in a constant-temperature water bath, and excessive aniline monomer is placed at the bottom in the closed container;
c) controlling the temperature of the constant temperature water bath at 50 ℃ and the vacuum degree in the closed container at 0.06MPa to evaporate aniline monomer at the bottom of the closed containerForming aniline vapor with a certain concentration, and oxidizing agent (NH) on the positive plate4)2S2O8Contacting with protonic acid HCl to generate proton exchange and in-situ polymerization, forming a conductive polyaniline film with the thickness of 150nm on the surface of a positive electrode material layer of a positive plate after 48 hours, taking out the positive plate, rapidly immersing the positive plate in an alcohol-water mixed solvent, rapidly taking out the positive plate, washing off redundant impurities on the surface for three times, and performing vacuum drying at 80 ℃ for 24 hours to obtain the conductive polymer film double-sided modified LiFePO4And a positive plate.
The obtained conductive polymer film is subjected to double-sided modification of LiFePO4The positive plate is matched with a graphite negative electrode, and a cylindrical battery is assembled by taking Celgard2400 as a diaphragm. The battery is subjected to capacity grading and testing in a battery testing system, as shown in fig. 4 and 5, the charging and discharging cut-off voltage is 2.0-3.65V, the discharging specific capacity of the obtained battery is greatly improved compared with that of an unmodified material, and the charging and discharging platform voltage is improved and stable.
Example 3
The positive pole piece of this embodiment includes the positive plate that is formed by the mass flow body and the positive electrode material layer that adheres to current collector one side, still adhere to the conducting polymer membrane on the positive plate outside positive electrode material layer.
The preparation method of the positive pole piece of the embodiment comprises the following steps:
a) preparing a positive plate: taking an S/C composite positive electrode material as a positive electrode active substance, polytetrafluoroethylene as a water-based binder and superconducting carbon black as a conductive agent, uniformly mixing the positive electrode active substance, the binder and the conductive agent according to the mass ratio of 7:3:1, adding a proper amount of NMP as a solvent to prepare a slurry, uniformly coating the slurry on an aluminum foil, and performing vacuum drying at 60 ℃ for 12 hours to form a positive electrode material layer on the aluminum foil to obtain a positive electrode plate;
b) uniformly coating a layer of initiator on the surface of the positive electrode material layer of the positive electrode plate obtained in the step 1), wherein the initiator is H with the concentration of 0.35mol/L2O2And CH at a concentration of 0.3mol/L3An aqueous solution of COOH;
in the vacuum evaporation coating device of the embodiment, like the embodiment 1, the positive plate coated with the initiator is placed in a closed container, the closed container is horizontally placed in a constant-temperature water bath, and excessive pyrrole monomers are placed at the bottom in the closed container;
c) controlling the temperature of the constant-temperature water bath to be 20 ℃ and the vacuum degree in the closed container to be 0.09MPa, evaporating pyrrole monomers at the bottom of the closed container, forming pyrrole vapor with a certain concentration in the closed container, wherein the pyrrole vapor and an oxidant H on the positive plate2O2And contacting with protonic acid acetic acid to perform proton exchange and in-situ polymerization reaction, forming a conductive polypyrrole film with the thickness of 20nm on the surface of the positive electrode material layer of the positive electrode plate after 70h, taking out the positive electrode plate, washing the surface with water, and performing vacuum drying at 60 ℃ for 36h to obtain the S/C positive electrode plate modified by the conductive polymer film.
Cutting the S/C positive plate modified by the obtained conductive polymer film, and tabletting to be used as a working electrode; and (3) taking the metal lithium as a negative electrode, and adding a proper amount of electrolyte to assemble the lithium-sulfur secondary battery. The battery is subjected to charge-discharge and cycle performance tests in a LAND battery test system, and the results are shown in FIGS. 6 and 7, wherein the charge-discharge cut-off voltage is 1-3V (vs. Li/Li)+) And compared with an unmodified material, the obtained battery has long cycle life and better cycle stability.
Claims (5)
1. The utility model provides a positive pole piece that conducting polymer membrane was decorated, includes the positive plate that is formed by the mass flow body and the positive electrode material layer of attaching to mass flow body one side or both sides, its characterized in that: the conductive polymer film is further attached to the outer side of the positive electrode material layer on the positive electrode plate;
the positive pole piece is prepared by the method comprising the following steps:
a) taking a positive plate, coating an initiator on the surface of a positive material layer of the positive plate, and placing the positive plate coated with the initiator in a closed container filled with a conductive polymer monomer;
b) controlling the vacuum condition of the closed container to evaporate the conductive polymer monomer, carrying out in-situ polymerization on the positive plate coated with the initiator to form a film, and drying the film to obtain the conductive polymer;
in the step a), the anode in the anode material layer is activatedThe material is LiFePO4、LiFePO4/C、LiMn2O4Or S/C;
in the step a), the conductive polymer monomer is pyrrole, thiophene or aniline;
in step b), the vacuum condition is as follows: the vacuum degree is 0.001-0.09 Mpa; the vacuum degree of the closed container is controlled by controlling the amount of the inert gas.
2. The conductive polymer film modified positive electrode sheet according to claim 1, wherein: in the step a), the initiator is an oxidant solution, and the oxidant solution contains an oxidant with the concentration of 0.1-1.0 mol/L.
3. The conductive polymer film modified positive electrode sheet according to claim 2, wherein: the oxidant is (NH)4)2S2O8、(NH4)2Ce(NO3)6、K2Cr2O7、Ce(SO4)2 .2(NH4)2SO4、FeCl3、H2O2Any one or combination thereof.
4. The conductive polymer film modified positive electrode sheet according to claim 2, wherein: the oxidant solution also contains protonic acid with the concentration of 0.07-0.3 mol/L.
5. The conductive polymer film modified positive electrode sheet according to claim 4, wherein: the protonic acid is H2SO4、HCl、HNO3、H3PO4、HCO3-、NH4+、CH3COOH, sulfonic acid group compound, benzene phosphoric acid, benzoic acid and any one of salicylic acid derivatives thereof.
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| CN107293752A (en) * | 2017-06-20 | 2017-10-24 | 燕山大学 | A kind of plating polyaniline that evaporates improves the method for negative plate of nickel-hydrogen battery chemical property |
| CN111509189A (en) * | 2019-01-30 | 2020-08-07 | 广州汽车集团股份有限公司 | Positive pole piece and lithium ion battery |
| CN112151792B (en) * | 2020-09-03 | 2022-05-17 | 浙江锋锂新能源科技有限公司 | High-nickel ternary cathode material and preparation method thereof |
| CN112448026A (en) * | 2020-11-23 | 2021-03-05 | 南京大学 | Composite sulfide solid electrolyte, battery and preparation method thereof |
| CN117117089B (en) * | 2023-10-23 | 2024-03-19 | 浙江帕瓦新能源股份有限公司 | Positive electrode of sodium ion battery, preparation method of positive electrode and sodium ion battery |
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