阅读说明：本技术 一种三维共轭导电聚苯胺的合成方法及作为锂离子电池负极粘结剂的应用 (Synthesis method of three-dimensional conjugated conductive polyaniline and application of three-dimensional conjugated conductive polyaniline as lithium ion battery cathode binder ) 是由 刘慰 何晓英 陈云贵 于 2020-11-13 设计创作，主要内容包括：本发明公开一种三维共轭导电聚苯胺的合成方法及作为锂离子电池负极粘结剂的应用。三维共轭导电聚苯胺的合成包括以下内容：配制质子酸水溶液或共掺杂剂与质子酸的混合水溶液,将苯胺、共聚单体溶解在质子酸溶液中形成溶液,记为A组分；将引发剂溶解在去离子水中,记为B组分；在冰浴0～4℃条件下将B组分缓慢滴加到A组分中,继续搅拌聚合4～8h；然后用乙醇和去离子水洗涤,直至滤液呈中性,将滤饼干燥即得三维共轭导电聚苯胺。本发明还提供了基于上述方法的负极材料/三维共轭导电聚苯胺复合浆料的原位制备方法。本发明制备的聚苯胺具有良好的粘接能力和导电性,能够同时作为导电剂和粘接剂,并能显著提升锂离子电池的循环稳定性。(The invention discloses a synthesis method of three-dimensional conjugated conductive polyaniline and application of the three-dimensional conjugated conductive polyaniline as a lithium ion battery cathode binder. The synthesis of the three-dimensional conjugated conductive polyaniline comprises the following contents: preparing protonic acid aqueous solution or mixed aqueous solution of a codopant and protonic acid, and dissolving aniline and a comonomer in the protonic acid aqueous solution to form solution which is marked as component A; dissolving an initiator in deionized water, and marking as a component B; slowly dripping the component B into the component A at the temperature of 0-4 ℃ in an ice bath, and continuously stirring for polymerization for 4-8 h; and then washing with ethanol and deionized water until the filtrate is neutral, and drying the filter cake to obtain the three-dimensional conjugated conductive polyaniline. The invention also provides an in-situ preparation method of the cathode material/three-dimensional conjugated conductive polyaniline composite slurry based on the method. The polyaniline prepared by the method has good bonding capability and conductivity, can be used as a conductive agent and an adhesive at the same time, and can remarkably improve the cycle stability of a lithium ion battery.)

1. A method for synthesizing three-dimensional conjugated conductive polyaniline is characterized by comprising the following steps:

preparing protonic acid aqueous solution or mixed aqueous solution of a codopant and protonic acid, dissolving aniline and a comonomer in the protonic acid aqueous solution to form solution, marking as component A, wherein the molar ratio of aniline to comonomer is 1: (0.1-3), wherein the molar ratio of aniline to protonic acid is 1: (0.05-3), wherein the molar ratio of the aniline to the codoping agent is 1: (0.05-3); dissolving an initiator in deionized water, and marking as a component B; slowly dripping the component B into the component A at the temperature of 0-4 ℃ in an ice bath, and continuously stirring for polymerization for 4-8 h; and then washing with ethanol and deionized water until the filtrate is neutral, and drying the filter cake to obtain the three-dimensional conjugated conductive polyaniline.

2. The method of claim 1, wherein the comonomer is at least one of m-phenylenediamine, o-phenylenediamine, 1,3, 5-triphenylanilinobenzene, 1,3, 5-triaminobenzene, and p-diaminobiphenyl.

3. The method of claim 1, wherein the co-dopant is a chloride salt.

4. The method of claim 1, wherein the initiator is at least one of ammonium persulfate, sodium persulfate, and potassium persulfate; the molar ratio of aniline to initiator is 1: (0.05-1).

5. The method of claim 1, wherein the protonic acid is at least one of hydrochloric acid, sulfuric acid, and phosphoric acid.

6. The three-dimensional conjugated conducting polyaniline prepared by the method of any one of claims 1 to 5.

7. The use of the three-dimensional conjugated conducting polyaniline of claim 6 as a conducting agent and binder in a negative electrode of a lithium ion battery, comprising a graphite negative electrode, a hard carbon negative electrode, a soft carbon negative electrode, a silicon carbon negative electrode, and a silicon negative electrode.

8. An in-situ preparation method of a negative electrode material/three-dimensional conjugated conductive polyaniline composite slurry is characterized by comprising the following steps:

adding a negative electrode active material, aniline and a comonomer into a protonic acid aqueous solution or a mixed aqueous solution of a co-doping agent and protonic acid, and marking as a component A, wherein the using amount of the negative electrode active material is 50-90 wt% of the total solid content of the negative electrode active material and polyaniline, and the molar ratio of the aniline to the comonomer is 1: (0.1-3), wherein the molar ratio of aniline to protonic acid is 1: (0.05-3), wherein the molar ratio of the aniline to the codoping agent is 1: (0.05-3); dissolving an initiator in deionized water, and marking as a component B; slowly dripping the component B into the component A at the temperature of 0-4 ℃ in an ice bath, and continuously stirring for polymerization for 4-8 h; the viscosity of the slurry is regulated and controlled by controlling the concentration of the component A, so that the cathode active material/three-dimensional conjugated conductive polyaniline composite slurry is obtained.

9. The method of claim 8, wherein the comonomer is at least one of m-phenylenediamine, o-phenylenediamine, 1,3, 5-triphenylanilinobenzene, 1,3, 5-triaminobenzene, and p-diaminobiphenyl; the negative active material is at least one of graphite powder, hard carbon powder, soft carbon powder, silicon carbon powder and nano silicon powder; the codopant is a chloride salt; the initiator is at least one of ammonium persulfate, sodium persulfate and potassium persulfate; the protonic acid is at least one of hydrochloric acid, sulfuric acid and phosphoric acid.

10. A lithium ion battery cathode is characterized in that the cathode material/three-dimensional conjugated conductive polyaniline composite slurry prepared by the method of claim 8 or 9 is coated on a copper foil, dried in vacuum at 120 ℃ for 12-24 hours, and washed by ethanol and water to obtain the lithium ion battery cathode.

Technical Field

The invention belongs to the technical field of electrode binder materials, and particularly relates to synthesis and electrode application of a three-dimensional conjugated conductive polyaniline binder for a lithium ion battery cathode.

Background

With the development of society, lithium ion batteries are widely used in a plurality of fields such as mobile electronic equipment, electric vehicles, power grid energy storage and the like due to the advantages of high energy density, high working voltage, long cycle life and the like. However, the rapid development of new energy industry also puts higher requirements on the performance of lithium ion batteries, and the current commercialized negative electrode material is gradually transited from graphite, hard carbon and soft carbon to the development of a silicon-carbon composite negative electrode material system so as to further meet the battery performance requirements of higher specific energy and longer cycle life. The negative active material is usually matched with a conductive agent (generally one or more of carbon black, ketjen black, carbon nanotube, graphene, etc.) and a binder (generally one or more of styrene butadiene rubber latex SBR, carboxymethyl cellulose CMC, polyacrylic acid PAA, etc.) to be coated and formed by matching with electrode paste and promote electron transmission in the electrode sheet [ Journal of Power Sources,2014,257: 421-. With the gradual increase of the specific gram capacity of the negative electrode material, especially the introduction of high-gram capacity components such as silicon, a large volume expansion effect is caused in the cycle process of the negative electrode [ Advanced Energy Materials,2018,8(11):1702314 ]. The high-performance negative electrode adhesive is developed, the tolerance capability of the negative electrode sheet to large-volume deformation is improved, and the high-performance negative electrode adhesive has very important application value.

As an important part of the electrode, the properties of the binder have a crucial influence on the electrochemical performance of the electrode sheet. The traditional SBR-CMC bonding system is easy to cause rapid capacity attenuation and short cycle life when applied to a silicon cathode due to the larger brittleness and insulativity; meanwhile, the bonding system is an electronic insulator and needs to be matched with a certain content of conductive agent for use, the use of the conductive agent can reduce the energy density of the battery, and the cost is increased. Songjie et al have disclosed a polymer composite binder, which utilizes the mutual compounding of linear polymer and sheet layer polymer to establish a three-dimensional network structure around the silicon negative electrode material through hydrogen bonds, thereby buffering the volume change [ CN108428869B ]; the traditional sodium alginate binder is modified by graphene quantum dots by Zhangijia and the like, so that the traditional sodium alginate binder has higher mechanical property and elastic property, the swelling property of the traditional sodium alginate binder is enhanced, and the volume change of a negative electrode material is effectively relieved; and the graphene quantum dots have conductivity, and meanwhile, the conductivity of the binder is improved [ CN108565406B ]. In general, the adhesion or conductivity can be effectively improved by using a novel polymer composite binder or modifying a conventional binder, however, these methods have disadvantages in that: (1) most polymer composite binders have good binding capacity but show insulativity, and when the polymer composite binders are applied to lithium ion battery cathode slurry, a conductive agent needs to be additionally added; (2) the modification of the traditional adhesive can effectively improve the adhesive capacity and the electrical conductivity, but increases the preparation steps, so that the application of the traditional adhesive in the industry is limited, and the production cost is increased.

Disclosure of Invention

The invention aims to provide a synthetic method of three-dimensional conjugated conductive polyaniline and application of the three-dimensional conjugated conductive polyaniline as a lithium ion battery cathode binder aiming at the defects of the prior art, wherein the polyaniline has good bonding capability and conductivity, and further the cycle stability of a lithium ion battery is remarkably improved.

The invention provides a method for synthesizing three-dimensional conjugated conductive polyaniline, which comprises the following steps:

preparing protonic acid aqueous solution or mixed aqueous solution of a codopant and protonic acid, and dissolving aniline and a comonomer in the protonic acid aqueous solution to form solution which is marked as component A; dissolving an initiator in deionized water, and marking as a component B; slowly dripping the component B into the component A at the temperature of 0-4 ℃ in an ice bath, and continuously stirring for polymerization for 4-8 h; and then washing with ethanol and deionized water until the filtrate is neutral, and drying the filter cake to obtain the three-dimensional conjugated conductive polyaniline.

In the above method, the comonomer is at least one of m-phenylenediamine, o-phenylenediamine, 1,3, 5-triphenylanilino-benzene, 1,3, 5-triaminobenzene, and p-diaminobiphenyl. The structural formula of each comonomer is as follows:

in the above method, further, the co-dopant is a chloride salt, preferably hydrogen chloride and lithium chloride.

In the above method, the molar ratio of aniline to comonomer is 1: (0.1-3), wherein the molar ratio of aniline to protonic acid is 1: (0.05-3), wherein the molar ratio of the aniline to the codoping agent is 1: (0.05-3).

In the above method, further, the initiator is at least one of ammonium persulfate, sodium persulfate and potassium persulfate; the molar ratio of aniline to initiator is 1: (0.05-1).

In the above method, the protonic acid is at least one of hydrochloric acid, sulfuric acid and phosphoric acid.

In the method, the filter cake is further dried under vacuum at 120 ℃ for 12-24 hours.

The invention provides the three-dimensional conjugated conductive polyaniline prepared by the method. The conductive polyaniline adhesive has a three-dimensional macromolecular structure with intramolecular conjugation such as branching, crosslinking and the like, and has good adhesion and conductivity which can reach 1 x 10^-6～1×10^-2S/cm。

The invention also provides application of the three-dimensional conjugated conductive polyaniline binder in a lithium ion battery cathode.

In the above application, further, the negative electrode of the lithium ion battery includes a graphite negative electrode, a hard carbon negative electrode, a soft carbon negative electrode, a silicon carbon negative electrode and a silicon negative electrode.

The above use, further, is as both a conductive agent and an adhesive.

The invention provides an in-situ preparation method of a negative electrode material/three-dimensional conjugated conductive polyaniline composite slurry, which comprises the following steps:

adding a negative electrode active material, aniline and a comonomer into a protonic acid aqueous solution or a mixed aqueous solution of a co-doping agent and protonic acid, and marking as a component A, wherein the using amount of the negative electrode active material is 50-90 wt% of the total solid content of the negative electrode active material and polyaniline; dissolving an initiator in deionized water, and marking as a component B; slowly dripping the component B into the component A at the temperature of 0-4 ℃ in an ice bath, and continuously stirring for polymerization for 4-8 h; the viscosity of the slurry is regulated and controlled by controlling the concentration of the component A, so that the cathode active material/three-dimensional conjugated conductive polyaniline composite slurry is obtained.

In the above method, the comonomer is at least one of m-phenylenediamine, o-phenylenediamine, 1,3, 5-triphenylanilino-benzene, 1,3, 5-triaminobenzene, and p-diaminobiphenyl.

In the above method, further, the co-dopant is a chloride salt, preferably hydrogen chloride and lithium chloride.

In the above method, the molar ratio of aniline to comonomer is 1: (0.1-3), wherein the molar ratio of aniline to protonic acid is 1: (0.05-3), wherein the molar ratio of the aniline to the codoping agent is 1: (0.05-3).

In the above method, further, the initiator is at least one of ammonium persulfate, sodium persulfate and potassium persulfate; the molar ratio of aniline to initiator is 1: (0.05-1).

In the above method, the protonic acid is at least one of hydrochloric acid, sulfuric acid and phosphoric acid.

In the above method, the negative active material is at least one of graphite powder, hard carbon powder, soft carbon powder, silicon carbon powder, and nano silicon powder.

The invention provides a preparation method of a lithium ion battery cathode based on the three-dimensional conjugated conductive polyaniline adhesive, which comprises the steps of coating the cathode material/three-dimensional conjugated conductive polyaniline composite slurry prepared by the invention on a copper foil, carrying out vacuum drying at 120 ℃ for 12-24 h to obtain a cathode active material/three-dimensional conjugated conductive polyaniline pole piece, washing the pole piece with ethanol and water to remove residual acid and unreacted monomers, and obtaining the pole piece.

The invention provides a lithium ion battery cathode prepared by the method.

The invention has the beneficial effects that:

1. the invention adopts an in-situ chemical oxidation method as a main method to prepare the conductive polyaniline adhesive with an intramolecular conjugated three-dimensional conjugated macromolecular structure. Compared with the traditional electrode bonding system, the conductive polyaniline binder prepared by the invention has the following advantages when used as the lithium ion battery cathode binder: (1) the good adhesive property between the active substance and the current collector is effectively improved, the conductivity of the negative electrode material and the binding force between the negative electrode material and the current collector are improved, the tolerance of the negative electrode plate to volume expansion and strain is improved by the three-dimensional conjugated structure, and the pole plate pulverization and the falling-off of the active substance are inhibited; the characteristics of high capacity, long service life and high cycle stability are displayed; (2) the electrode plate can be endowed with good electronic conductivity under the condition of not using any conductive additive, and simultaneously has double roles of a conductive agent and a binder, so that the use of the conductive agent is completely avoided, and meanwhile, the active material and a current collector can form strong bonding force, the structural stability in the electrode circulation process is improved, the battery circulation life is prolonged, and the capacity retention rate is improved; (3) in the synthesis process, the composite material is compounded with the cathode active material in situ and prepared into slurry, so that the experimental steps are simplified, and the cycling stability of the cathode material is improved.

2. The material prepared by the method can be compatible and universal with the traditional pole piece manufacturing and battery assembling process equipment in the subsequent pole piece manufacturing, battery assembling and other processes, and is suitable for large-scale industrial application.

3. The method disclosed by the invention is simple to operate, high in yield and capable of realizing industrial large-scale preparation.

Drawings

Fig. 1 is a general molecular structural view of three-dimensional conjugated polyaniline;

fig. 2(a) is a charge-discharge curve of the electrode sheet formed in situ of graphite and three-dimensional conjugated conductive polyaniline in example 1; fig. 2(b) is a charge-discharge curve of the electrode sheet prepared from the three-dimensional conjugated polyaniline and the nano-silicon in example 5;

fig. 3 is an SEM image of the three-dimensional conjugated conductive polyaniline powder of example 5;

fig. 4 is a cycle characteristic diagram of the three-dimensional conjugated polyaniline/nano-silicon electrode sheet and the conventional nano-silicon electrode sheet in example 5;

FIG. 5 is a photograph of the current collectors of the three-dimensional conjugated polyaniline/nano-silicon electrode sheet (a) and the conventional CMC-CB nano-silicon electrode sheet (b) of example 5 before and after the peel strength test

Detailed Description

The present invention is further illustrated by the following specific examples. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without any creative effort belong to the protection scope of the present invention.

Example 1

The synthesis method of the three-dimensional conjugated conductive polyaniline for the graphite cathode comprises the following steps:

weighing 9.3g of aniline, 2.7g of p-phenylenediamine and 6.15g of 1,3, 5-triaminobenzene monomer, dissolving in 40ml of 0.5mol/L hydrochloric acid aqueous solution, magnetically stirring for 1h at the constant temperature of 4 ℃, and performing proper ultrasonic dispersion to obtain a component A; weighing 11.4g of ammonium persulfate, dissolving in 20ml of deionized water to obtain a component B, slowly adding the component B into the component A dropwise, continuing stirring and polymerizing for 4 hours after the dropwise addition is finished, finally centrifugally separating a product, washing the product with ethanol and deionized water until filtrate is neutral, and performing vacuum drying for 12 hours at 120 ℃ to obtain the three-dimensional conjugated conductive polyaniline powder. The powder is subjected to compression molding to obtain a polyaniline sheet, and the conductivity of the polyaniline sheet is 3.0 multiplied by 10 through a four-probe conductivity test^-3S/cm. The structural formula of the prepared three-dimensional conjugated polyaniline is shown in figure 1, and the structural formula is characterized in that aniline structural units are mutually interwoven to form a large-ring-shaped three-dimensional conjugated molecular structure, so that the electron delocalization conjugation range is greatly improved, the formation of a high-conductivity polyaniline adhesive is promoted, and the capacity exertion of a pole piece is improved.

Preparing graphite/three-dimensional conjugated conductive polyaniline composite slurry:

weighing 9.3g of aniline, 2.7g of p-phenylenediamine and 6.15g of 1,3, 5-triaminobenzene monomer, dissolving in 40ml of 0.5mol/L hydrochloric acid aqueous solution, adding 100g of negative graphite powder, placing at the constant temperature of 4 ℃, magnetically stirring for 1 hour, and performing proper ultrasonic dispersion to obtain a component A; weighing 11.4g of ammonium persulfate, dissolving in 20ml of deionized water to obtain a component B, slowly adding the component B into the component A dropwise, continuing stirring and polymerizing for 4 hours after the dropwise addition is finished, and controlling the consistency of the slurry to obtain the graphite/three-dimensional conjugated conductive polyaniline composite slurry.

Uniformly coating the prepared graphite/three-dimensional conjugated conductive polyaniline composite slurry on a copper foil, carrying out vacuum drying for 12h in a vacuum drying oven at 120 ℃, and cutting a pole piece into piecesAfter the wafer is soaked and washed by ethanol, the wafer is put into a glove box filled with argon, and the water content and the oxygen content of the wafer are less than 0.1ppm, and the wafer is taken as a working electrode, and a metal lithium sheet is taken as a counter electrode and a reference electrode to assemble a battery. The electrolyte used was EC, DEC EMC 1:1:1, 5% FEC, 1M LiPF₆And Celgard 2400 is a diaphragm, and a CR2025 battery shell, a 0.5mm gasket and a 1.0mm elastic sheet are assembled into the button cell.

And (3) using a LAND battery test system to perform cycle performance test on the assembled button cell at a current density of 100mA/g, wherein the voltage window is 0.01V-2.5V. After the electrode is circulated for 50 circles under the current density of 100mA/g, the discharge specific capacity is 262mAh/g, and the capacity retention rate is 80%. The charge and discharge curve is shown in figure 2 a.

For comparison, using 9.3g of aniline and 2.325g of triphenylamine as comonomers, corresponding polyaniline and electrode sheet were prepared in the same manner as in example 1 except for the process conditions. And then, after 50 cycles of circulation are carried out under the same test condition of 100mA/g current density, the specific capacity of the graphite is 225mAh/g, and the capacity retention rate is 68%. In this comparison, the structural formula of the obtained branched polyaniline is as follows:

for comparison, the specific capacity of the graphite pole piece of the conventional CB-CMC conductive agent-binder system is 185mAh/g after 50 cycles of circulation under the same test condition, and the capacity retention rate is 58%.

As can be seen from the comparison of example 1, in the polyaniline prepared in example 1, the aniline structural unit forms a large ring-shaped three-dimensional conjugated cross-linked molecular structure, and compared with the conventional linear or branched polyaniline, the three-dimensional conjugated molecular structure not only can promote the improvement of the conductivity, but also can greatly improve the adhesive strength of the polyaniline in the electrode sheet, thereby improving the capacity exertion and the cycling stability of the negative electrode graphite.

Example 2

A method for synthesizing and applying a three-dimensional conjugated conductive polyaniline binder for a silicon cathode.

A method for synthesizing three-dimensional conjugated conductive polyaniline used for a nano silicon cathode comprises the following steps:

adding 9.12g of lithium chloride solid, 4.65g of aniline monomer and 6.15g of 1,3, 5-triaminobenzene into 50ml of hydrochloric acid aqueous solution with the concentration of 1mol/L, stirring and dissolving together, and placing the mixture at the constant temperature of 4 ℃ for magnetic stirring for 1h to dissolve completely to obtain a component A; weighing 4.56g of ammonium persulfate, dissolving in 10ml of deionized water, and obtaining a component B after the ammonium persulfate is completely dissolved; slowly adding the component B into the solution dropwise, continuing stirring and polymerizing for 4 hours after the dropwise addition is finished, finally centrifugally separating the product, washing the product with ethanol and deionized water until the filtrate is neutral, and drying the product in vacuum at 120 ℃ for 12 hours to obtain Li⁺Proton double-doped three-dimensional conjugated conductive polyaniline powder. The powder is subjected to compression molding to obtain a polyaniline sheet, and the conductivity of the polyaniline sheet is 3.65 multiplied by 10 through a four-probe conductivity test^-4S/cm. The structure of the prepared polyaniline was similar to that of example 1.

Preparing nano silicon/three-dimensional conjugated conductive polyaniline composite slurry:

adding 15g of nano silicon powder into 25ml of 1mol/L hydrochloric acid aqueous solution, and performing ultrasonic dispersion for 1 hour; then weighing 4.56g of lithium chloride solid, 2.32g of aniline monomer and 3.1g of 1,3, 5-triaminobenzene, stirring and dissolving in the nano silicon-hydrochloric acid aqueous solution, placing the solution at the constant temperature of 4 ℃ and stirring for 1 hour by magnetic force, and performing proper ultrasonic dispersion to obtain a component A; weighing 4.56g of ammonium persulfate, dissolving in 10ml of deionized water, and obtaining a component B after the ammonium persulfate is completely dissolved; and slowly adding the component B into the component A dropwise, and continuously stirring and polymerizing for 4 hours at the constant temperature of 4 ℃ after the dropwise addition is finished to obtain the nano silicon/three-dimensional conjugated conductive polyaniline composite slurry. And uniformly coating the prepared nano silicon/three-dimensional conjugated conductive polyaniline composite slurry on a copper foil, and performing vacuum drying in a vacuum drying oven at 120 ℃ for 12 hours. Cutting the pole piece intoThe wafer is soaked and washed by ethanol, and then is put into a glove box filled with argon, the water content and the oxygen content of which are less than 0.1ppm, and the glove box is used as a working electrode and a metal lithium sheet as a counter electrode and a reference electrode to assemble a battery, wherein the electrolyte is EC, DEC, EMC 1:1:1, 5% FEC, 1M LiPF6 and Celgard 2400 are used as a diaphragm, and a CR2025 battery shell, a 0.5mm gasket and a 1.0mm elastic sheet are used to assemble a button battery.

And (3) using a LAND battery test system to perform cycle performance test on the assembled button cell at a current density of 100mA/g, wherein the voltage window is 0.01V-2.5V. After the electrode is cycled for 50 circles under the current density of 100mA/g, the discharge specific capacity is 1790.4mAh/g, and the capacity retention rate is as high as 70%.

For comparison, the conventional CB-CMC conductive agent-adhesive system nano silicon pole piece is used, the discharge specific capacity is 1500mAh/g under the same test condition, and the capacity retention rate is 60%.

Example 3

The synthesis method of the three-dimensional conjugated conductive polyaniline for the nano silicon cathode comprises the following steps:

respectively weighing 0.93g of aniline, 0.31g of o-phenylenediamine and 0.2g of 1,3, 5-triphenylanilino benzene monomer, dissolving in 10ml of 0.5mol/L hydrochloric acid aqueous solution, and magnetically stirring for 1h at the constant temperature of 4 ℃ to obtain a component A; 1g of ammonium persulfate was weighed and dissolved in 20ml of deionized water to obtain a B component. And (3) dropwise adding the component B into the component A at a low speed, continuously stirring and polymerizing for 4 hours at a constant temperature of 4 ℃ after dropwise adding, finally centrifugally separating a product, washing the product with ethanol and deionized water until the filtrate is neutral, and drying for 12 hours in vacuum at 120 ℃ to obtain the three-dimensional conjugated conductive polyaniline powder. The powder is subjected to compression molding to obtain a polyaniline sheet, and the conductivity of the polyaniline sheet is 7.96 multiplied by 10 through a four-probe conductivity test^-5S/cm. The structure of the prepared polyaniline was similar to that of example 1.

Preparing nano silicon/three-dimensional conjugated conductive polyaniline composite slurry:

respectively weighing 0.93g of aniline, 0.31g of o-phenylenediamine, 0.2g of 1,3, 5-triphenylamine aminobenzene monomer and 5g of nano silicon powder, stirring and ultrasonically dispersing in 10ml of hydrochloric acid aqueous solution with the concentration of 0.5mol/L, and placing the mixture in a constant temperature of 4 ℃ for magnetic stirring for 1 hour to obtain a component A; 1g of ammonium persulfate was weighed and dissolved in 20ml of deionized water to obtain a B component. And slowly adding the component B into the component A dropwise, and continuously stirring and polymerizing for 4 hours at the constant temperature of 4 ℃ after the dropwise addition is finished to obtain the nano silicon/three-dimensional conjugated conductive polyaniline composite slurry.

And uniformly coating the prepared nano silicon/three-dimensional conjugated conductive polyaniline composite slurry on a copper foil, and performing vacuum drying in a vacuum drying oven at 120 ℃ for 12 hours. Cutting the pole piece intoAfter the wafer is soaked and washed by ethanol, the wafer is put into a glove box filled with argon, and the water content and the oxygen content of the wafer are less than 0.1ppm, and the wafer is taken as a working electrode, and a metal lithium sheet is taken as a counter electrode and a reference electrode to assemble a battery. The electrolyte used was EC: DEC: EMC 1:1:1, 5% FEC, 1M LiPF6, Celgard 2400 was a separator, and a button cell was assembled using a CR2025 cell case, 0.5mm gaskets, and 1.0mm spring plates.

And (3) using a LAND battery test system to perform cycle performance test on the assembled button cell under the current densities of 100mA/g and 500mA/g, wherein the voltage window is 0.01V-2.5V. After the electrode is circulated for 50 circles under the current density of 100mA/g, the discharge specific capacity is 2096mAh/g, and the capacity retention rate is up to 76%. When the current density of 500mA/g is adopted for 100 cycles, the discharge specific capacity of 1169mAh/g can still be achieved.

For comparison, after the nano silicon pole piece of the conventional CB-CMC conducting agent-binder system is circulated for 50 circles under the current density of 100mA/g, the specific discharge capacity is 1220mAh/g, and the capacity retention rate is 59%. When the current density of 500mA/g is adopted for 100 cycles, the discharge specific capacity is only 1020mAh/g, and the capacity retention rate is 50%.

Example 4

The synthesis method of the three-dimensional conjugated conductive polyaniline for the silicon-carbon composite cathode comprises the following steps:

0.93g aniline monomer and 1.23g 1,3, 5-triaminobenzene monomer are weighed and dissolved in 10ml aqueous solution with the concentration of 0.5mol/L hydrochloric acid and 0.5mol/L LiCl, and the solution is placed at the constant temperature of 4 DEG CMagnetically stirring for 1h to obtain a component A; weighing 1.2g of ammonium persulfate, and dissolving in 5ml of deionized water to obtain a component B; slowly adding the component B into the component A dropwise, continuing stirring and polymerizing for 4h at the constant temperature of 4 ℃ after dropwise addition is finished, finally centrifugally separating a product, washing the product with ethanol and deionized water until the filtrate is neutral, and performing vacuum drying for 12h at 120 ℃ to obtain three-dimensional conjugated conductive polyaniline powder, wherein an SEM picture is shown in an attached figure 3. The powder is subjected to compression molding to obtain a polyaniline sheet, and the conductivity of the polyaniline sheet is 6 multiplied by 10 through a four-probe conductivity test^-3S/cm. The structure of the prepared polyaniline was similar to that of example 1.

Preparing silicon carbon/three-dimensional conjugated conductive polyaniline composite slurry:

respectively weighing 0.93g of aniline, 1.23g of 1,3, 5-triaminobenzene monomer and 20g of silicon-carbon composite negative electrode powder (fibrate-SiC-1000), stirring and ultrasonically dispersing in 10ml of aqueous solution of 0.5mol/L hydrochloric acid and 0.5mol/L LiCl, and magnetically stirring for 1h at the constant temperature of 4 ℃ to obtain a component A; 1.2g of ammonium persulfate was weighed and dissolved in 5ml of deionized water to obtain component B. And slowly adding the component B into the component A dropwise, and continuously stirring and polymerizing for 4 hours at the constant temperature of 4 ℃ after the dropwise addition is finished to obtain the silicon-carbon/three-dimensional conjugated conductive polyaniline composite slurry.

Uniformly coating the prepared silicon-carbon/three-dimensional conjugated conductive polyaniline composite slurry on a copper foil, carrying out vacuum drying for 12h in a vacuum drying oven at 120 ℃, and cutting a pole piece into piecesAfter the wafer is soaked and washed by ethanol, the wafer is put into a glove box filled with argon, and the water content and the oxygen content of the wafer are less than 0.1ppm, and the wafer is taken as a working electrode, and a metal lithium sheet is taken as a counter electrode and a reference electrode to assemble a battery. The electrolyte used was EC, DEC EMC 1:1:1, 5% FEC, 1M LiPF₆And Celgard 2400 is a diaphragm, and a CR2025 battery shell, a 0.5mm gasket and a 1.0mm elastic sheet are assembled into the button cell.

And (3) using a LAND battery test system to perform cycle performance test on the assembled button cell at a current density of 100mA/g, wherein the voltage window is 0.01V-2.5V. After the electrode is cycled for 50 circles under the current density of 100mA/g, the discharge specific capacity is 807mAh/g, and the capacity retention rate is up to 84%.

For comparison, 0.93g of aniline and 1.23g of triphenylamine monomer were dissolved in 10ml of aqueous solution with a concentration of 0.5mol/L hydrochloric acid +0.5mol/L LiCl and copolymerized, and other technical parameters were identical to those in example 4, and the corresponding electrodes were prepared. By adopting the same test method, after the obtained electrode is circulated for 50 circles under the current density of 100mA/g, the discharge specific capacity is 461mAh/g, and the capacity retention rate is 48%. In this comparison, the structural formula of the obtained polyaniline is as follows:

for comparison, the conventional graphite pole piece of the CB-CMC conducting agent-binder system has the specific discharge capacity of 450mAh/g and the capacity retention rate of 47 percent under the same test condition.

As can be seen from the comparison of example 4, in the polyaniline prepared in example 4, the structural unit of aniline forms a large-ring-shaped three-dimensional conjugated cross-linked molecular structure, and compared with polyaniline with a branched star-shaped structure obtained by polymerizing aniline and triphenylamine, the polyaniline prepared in example 4 has significantly improved conductivity, can exert higher adhesive strength and mechanical properties in an electrode plate, and improves the capacity exertion and cycling stability of a silicon-carbon negative electrode.

Example 5

The synthesis method of the three-dimensional conjugated conductive polyaniline of the nano silicon cathode comprises the following steps:

weighing 1.86g of aniline monomer and 2.45g of 1,3, 5-triaminobenzene monomer, dissolving in 10ml of 0.2mol/L hydrochloric acid aqueous solution, and magnetically stirring for 1h at the constant temperature of 4 ℃ to obtain a component A; weighing 2.28g of ammonium persulfate, and dissolving in 5ml of deionized water to obtain a component B; slowly adding the component B into the component A dropwise, continuing stirring and polymerizing for 4h at the constant temperature of 4 ℃ after dropwise addition is finished, finally centrifugally separating a product, washing the product with ethanol and deionized water until the filtrate is neutral, and performing vacuum drying for 12h at 120 ℃ to obtain three-dimensional conjugated conductive polyaniline powder, wherein an SEM picture is shown in an attached figure 3. The powder is subjected to compression molding to obtain polymerThe aniline sheet has conductivity of 3.8 × 10 by four-probe conductivity test^-3S/cm. The structure of the prepared polyaniline was similar to that of example 1. The SEM of the three-dimensional conjugated conductive polyaniline powder is shown in the figure, and the three-dimensional conjugated polyaniline powder can be seen from the figure 3, has the appearance characteristic of loose and porous, can promote the swelling and liquid retention capacity of the three-dimensional conjugated conductive polyaniline powder in electrolyte, and becomes an ideal electrode adhesive.

Preparing nano silicon/three-dimensional conjugated conductive polyaniline composite slurry:

respectively weighing 1.86g of aniline, 2.45g of 1,3, 5-triaminobenzene monomer and 20g of nano silicon powder, stirring and ultrasonically dispersing in 10ml of 0.2mol/L hydrochloric acid aqueous solution, and magnetically stirring for 1h at the constant temperature of 4 ℃ to obtain a component A; 2.28g of ammonium persulfate was weighed and dissolved in 5ml of deionized water to obtain component B. And slowly adding the component B into the component A dropwise, and continuously stirring and polymerizing for 4 hours at the constant temperature of 4 ℃ after the dropwise addition is finished to obtain the nano silicon/three-dimensional conjugated conductive polyaniline composite slurry.

Uniformly coating the prepared nano-silicon/three-dimensional conjugated conductive polyaniline composite slurry on a copper foil, carrying out vacuum drying for 12h in a vacuum drying oven at 120 ℃, and cutting a pole piece into piecesAfter the wafer is soaked and washed by ethanol, the wafer is put into a glove box filled with argon, and the water content and the oxygen content of the wafer are less than 0.1ppm, and the wafer is taken as a working electrode, and a metal lithium sheet is taken as a counter electrode and a reference electrode to assemble a battery. The electrolyte used was EC, DEC EMC 1:1:1, 5% FEC, 1M LiPF₆And Celgard 2400 is a diaphragm, and a CR2025 battery shell, a 0.5mm gasket and a 1.0mm elastic sheet are assembled into the button cell.

And finally, using a LAND battery test system to test the cycle performance of the assembled button battery at a current density of 100mA/g, wherein the voltage window is 0.01V-2.5V. After the electrode is cycled for 50 circles under the current density of 100mA/g, the discharge specific capacity is 2400.7mAh/g, and the capacity retention rate is 74%. The charge-discharge curve of the nano-silicon/three-dimensional conjugated conductive polyaniline composite electrode is shown in figure 2b, and the cycle characteristic diagram is shown in figure 4 (Si + PANi).

For comparison, 1.86g of aniline and 0.46g of triphenylamine were used as comonomers, and the corresponding polyaniline and electrode sheet were prepared under the same process conditions. And then the capacity of the nano silicon pole piece is 1125mAh/g after the nano silicon pole piece is circulated for 50 circles under the same test condition of 100mA/g current density, and the capacity retention rate is 34%. In this comparison, the structural formula of the obtained polyaniline is as follows:

for comparison, the specific capacity of the conventional CB-CMC nano silicon pole piece adopting a conductive agent-binder system is 685mAh/g after 50 cycles of circulation under the same test condition, and the capacity retention rate is 17%.

When the nano-silicon/three-dimensional conjugated conductive polyaniline composite electrode sheet prepared in example 5 was further subjected to a tape adhesion-tearing test, it was found that it exhibited significantly better current collector adhesion strength than the conventional CMC-CB adhesion system, as shown in fig. 5.

It can be known from the comparison of example 5 that, in the polyaniline prepared in example 5, the structural unit of aniline forms a large ring-shaped three-dimensional conjugated cross-linked molecular structure, and compared with the branched star-shaped polyaniline molecular structure obtained by polymerizing aniline and triphenylamine, the polyaniline has significant advantages in the adhesive strength and mechanical properties of the electrode sheet, and the three-dimensional conjugated conductive molecular structure can improve the capacity exertion and the cycling stability of the nano-silicon/polyaniline composite electrode.

As can be seen from fig. 1 to 4, the three-dimensional conjugated conductive polyaniline binder prepared by the invention not only can effectively improve the bonding strength between the active material and the current collector, but also can be used as a high-performance electrode conductive agent, thereby avoiding the use of a conductive agent which is difficult to disperse, and simplifying the preparation steps of the lithium ion battery cathode slurry; meanwhile, the three-dimensional conjugated conductive polyaniline binder prepared by the invention has a relatively stable molecular structure, can effectively relieve huge volume expansion of an active material in the charging and discharging processes, and the electrode plate prepared by the binder material has the characteristics of high capacity and high cycle stability in a lithium ion battery.