KR101982629B1 - Plant-derived pyrogallol-conjugated electrode binder and its manufacturing method for enhancing performance of lithium secondary battery - Google Patents

Abstract

The present invention relates to a secondary battery negative electrode material binder having a gel-type self-healing feature for improving lithium ion battery performance and a method of manufacturing the same. More specifically, by introducing pyrogallol functional groups, which are present in a large number of plants, into polymers, the polymer binders can be self-changed and self-healing in the form of gels, thereby increasing the durability of the negative electrode material. The present invention relates to a method of greatly improving the performance of a next-generation secondary battery using a silicon-based negative electrode material.

Description

Plant-derived pyrogalol functional group silicon negative electrode binder for improving lithium ion battery performance and its manufacturing method {Plant-derived pyrogallol-conjugated electrode binder and its manufacturing method for enhancing performance of lithium secondary battery}

The present invention relates to a secondary battery negative electrode material binder having a gel-type self-healing feature for improving lithium ion battery performance and a method of manufacturing the same. More specifically, by introducing pyrogallol functional groups, which are present in a large number of plants, into polymers, the polymer binders can be self-changed and self-healing in the form of gels, thereby increasing the durability of the negative electrode material. It is a method to greatly improve the performance of the next-generation secondary battery using a silicon-based negative electrode material.

Recently, researches are being actively conducted to develop a next-generation secondary battery far superior to that of a lithium-carbon based battery and to stably improve its performance. The research of the next-generation secondary battery is progressing toward developing a battery that is superior to the capacity of the existing lithium or carbon battery by changing the electrode material itself, rather than improving the performance of the existing lithium-carbon based battery. Among these, lithium-silicon-based batteries which have replaced the negative electrode of the carbon material with the negative electrode material of the silicon material have received great attention, which has a battery charging efficiency of about 10 times or more per unit mass of the silicon compared to the carbon, This is because it can greatly contribute to miniaturization and high capacity.

However, since the silicon negative electrode material expands / contracts largely due to the charge / discharge cycle of the battery, cracking and fragmentation of the electrode easily occur, which makes it difficult to maintain a long cycle life. In order to solve these shortcomings, various strategies for protecting the negative electrode material have been proposed. Among them, a so-called 'polymer binder' strategy that helps to maintain the shape of the electrode by mixing the polymer material at the electrode manufacturing stage has been in the spotlight. However, the conventional polymer binder strategy, which has been proposed, can be improved by simply taking the shape of the electrode itself. However, the limitation that the electrode damage itself due to the multiple charge / discharge cycles cannot be solved fundamentally is still solved. impossible.

Gelation is one of the characteristics of polymers in solution. It is a phase transition that shows the weaker flow phenomenon of liquid and closer to solid phase mainly due to weak cross-linking situation in polymer solution in aqueous solution. . These gel-type polymers have been widely used throughout the industry, mainly for use in bio / medical purposes such as small drug delivery capsules, artificial tissues and organ three-dimensional scaffolds.

However, the gelation of the polymer has a number of factors that affect the type and concentration of the polymer, the average molecular weight of the polymer, the degree of chemical and physical effects between the polymer, the interaction with the substances in the aqueous solution in the hydrated state, Polymers are very difficult to gelate themselves or are very demanding. Therefore, even if the polymer is highly optimized for a particular application purpose, there are many limitations in using the gelled polymer. Accordingly, various research directions for inducing gelation of polymers, such as a method of imparting a residue to a polymer or replacing an existing residue, or forcibly interconnecting a polymer through a compound treatment, have been proposed.

Plants have antioxidants that quickly oxidize themselves to protect other key substances from oxidation, to protect themselves from dangerous substances such as active electrons that occur during photosynthesis. These antioxidants are mainly catechins, tannins, and the like, and are derivatives of functional groups called pyrogallol. Since a functional group called pyrogallol is a substance which can be easily oxidized by only exposure to oxygen in the air, attempts to utilize such pyrogallol derivatives derived from plants have been actively conducted.

In order to solve the above problems, the present invention is to provide a pyrogalol functional group to the polymer and gelated, to provide a lithium-silicon-based next-generation secondary battery negative electrode material having a self-recovery capability and a method of manufacturing the same.

In order to solve the above problems, the present invention according to the first aspect provides a polymer compound into which a pyrogallol functional group is introduced.

The polymer compound may have a structure of any one of Formulas 1 to 3.

(Formula 1)

(Formula 2)

 (Formula 3)

In addition, the present invention according to the second aspect (a) mixing the raw polymer compound with a solvent to dissolve; (b) adding a compound having a pyrogallol functional group to the raw polymer compound solution and then stirring to introduce the pyrogallol functional group into the raw polymer compound; And (c) removing the unreacted material to obtain a polymer compound having a pyrogallol functional group introduced therein.

The raw polymer compound may include a carboxyl group (-COOH).

The raw polymer compound may have a structure of any one of the following Chemical Formulas 4 to 6.

(Formula 4)

(Formula 5)

(Formula 6)

The compound having a pyrogallol functional group may be a plant-derived compound.

The compound having a pyrogallol functional group may include an amino group (-NH ₂ ).

The compound having a pyrogallol functional group may have a structure of Formula 7 below.

(Formula 7)

Step (a) may include adding an active agent.

The active agent may comprise 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide (EDC).

The (c) unreacted material removing step may be a step of removing the unreacted material by using a semipermeable filtration membrane and then lyophilizing.

The present invention according to the third aspect also provides a polymer compound into which a pyrogallol functional group produced by the above method is introduced.

The present invention according to the fourth aspect also provides an electrode material comprising a high molecular compound into which a pyrogallol functional group is introduced.

In addition, the present invention according to the fifth aspect comprises the steps of: (i) dissolving the polymer compound in which the pyrogallol functional group is introduced into distilled water; And (ii) adding a silicon nanoparticle and a conductive compound to the polymer solution into which the pyrogallol functional group is introduced, thereby preparing a silicon electrode material. It provides a method of manufacturing.

The conductive compound may include ITO, silver nanowires, silver nanoparticles, carbon compounds, iron, copper, aluminum, gold, silver, nickel or tin.

In addition, the present invention according to the sixth aspect provides a silicon secondary battery electrode material using a polymer compound having a pyrogallol functional group introduced by the method as a binder.

In addition, the present invention according to the seventh aspect of the present invention comprises the steps of: (1) preparing an electrode by applying the silicon secondary battery electrode material of claim 16 to a copper thin film; And (2) provides a method for manufacturing a silicon secondary battery electrode comprising the step of cutting the electrode prepared in the step (1) to form a insertable into the battery.

The copper thin film may have a thickness of 5 ~ 20 ㎛.

The present invention according to the eighth aspect also provides a silicon secondary battery electrode produced by the above method.

The polymer compound into which the pyrogallol functional group according to the present invention is introduced and the silicon secondary battery using the polymer compound as a binder can significantly reduce the lifespan reduction effect due to volume expansion, which is a disadvantage of the conventional silicon secondary battery. In addition, by giving the pyrogalol functional group a variety of physical and chemical interaction force that the conventional general polymer binder does not have, the overall stability of the silicon electrode can be greatly improved.

1 is a diagram illustrating a series of processes for introducing pyrogallol amine by activating a carboxyl functional group, which is a functional group of a polymer.
FIG. 2 is a graph confirming that pyrogallol was successfully introduced into the polymer by measuring absorbance of the polymer into which the pyrogallol functional group was introduced through FIG. 1.
Figure 3 (A) ~ (B) is a graph showing the ability to maintain the charge capacity according to the number of charge and discharge cycle of the battery by producing a lithium half-cell using a silicon electrode using a polymer in which the pyrogallol functional group introduced in Figure 1 as a binder (C) is a graph confirming the ability to maintain the charge capacity according to the charge-discharge rate for the silicon electrode using the hyaluronic acid polymer in which the pyrogallol functional group introduced polymer of the pyrogallol functional group of Figure 1 introduced as a binder.
FIG. 4 shows five charge / discharge cycles of a silicon electrode using pyrogallol-introduced hyaluronic acid polymer as a binder, and then a hyaluronic acid polymer without pyrogallol is used as a binder. In addition to the silicon electrode, the degree of damage to the carboxymethyl cellulose binder, which has been studied with the conventional silicone binder, was compared and observed through a scanning electron microscope.
FIG. 5 is a graph of a near-infrared absorbance analysis for confirming the physical interaction between the hyaluronic acid polymer and the silicon nanoparticles to which the pyrogallol functional group is introduced.
6 is a graph confirming the degree of rheological change over time with respect to the polymer solution of the same concentration as the electrode fabrication environment in order to confirm the natural gelation of the hyaluronic acid polymer introduced with a pyrogallol functional group.
FIG. 7 is a natural gelling of a hyaluronic acid polymer having a pyrogallol functional group introduced therein, to demonstrate that a strong net-like binder structure with electrode materials such as silicon nanoparticles is formed during electrode fabrication using the polymer as a binder. It is an image observed with an electron microscope.
FIG. 8 is a profile monomolecule introduced by pyrogallol through high performance liquid chromatography to confirm that the hyaluronic acid polymer into which the pyrogallol functional group is introduced forms a covalent bond by autooxidation of pyrogallol to increase the overall molecular weight. It is a graph confirming retention time before and after oxygen exposure of rate.
9 is prepared by preparing an aqueous solution of propylgallate, which is a model single molecule of a pyrogallol introduced polymer, to indirectly prove a mechanism in which a hyaluronic acid polymer into which a pyrogallol functional group is introduced is covalently formed by autooxidation of pyrogallol, It is a mass spectrometry graph that forms dimers by forming covalent bonds by natural oxidation.

Hereinafter, a preferred embodiment of the present invention will be described in detail. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted. Throughout the specification, when a part is said to "include" a certain component, it means that it may further include other components, not to exclude other components, unless otherwise stated.

The present inventors confirmed that by introducing a pyrogallol functional group into a commercially available polymer compound, a secondary battery polymer binder capable of easily crosslinking polymers without additional oxidizing agent treatment can be prepared. In addition, the polymer binder in which the pyrogallol functional group is introduced has greatly enhanced the interaction force between the polymer chains, and it is confirmed that the polymer binder can easily induce gelation and has self-healing ability. In addition, by utilizing the polymer compound binder in which the pyrogallol functional group according to the present invention is introduced in a silicon-based next-generation secondary battery, it was confirmed that the life performance of the secondary battery was greatly improved and the present invention was completed.

Hereinafter, the present invention will be described in detail.

The present invention provides a polymer in which a pyrogallol functional group is introduced by reacting a pyrogallol compound having an amine group with a polymer compound having a carboxyl group as a functional group, and a method of manufacturing the same.

The present invention according to the first aspect provides a polymer compound into which a pyrogallol functional group is introduced.

The polymer compound may have a structure of any one of Formulas 1 to 3.

(Formula 1)

(Formula 2)

 (Formula 3)

The present invention according to the second aspect comprises the steps of (a) mixing the raw polymer compound with a solvent to dissolve it; (b) adding a compound having a pyrogallol functional group to the raw polymer compound solution and then stirring to introduce the pyrogallol functional group into the raw polymer compound; And (c) removing the unreacted material to obtain a polymer compound having a pyrogallol functional group introduced therein.

Hereinafter, the manufacturing method will be described in detail for each step.

In the production method according to the present invention, step (a) is a step of preparing a raw polymer compound solution by dissolving the raw polymer compound in a solvent.

The raw polymer compound may have a concentration of 0.1 to 1% by weight in the solvent, more preferably may have a concentration of 0.5% by weight. In addition, the molecular weight of the raw polymer compound may be 4,000 ~ 1,000,000, preferably the molecular weight may be 200,000.

In addition, the raw polymer compound may include a carboxyl group (-COOH). The carboxyl group reacts with the amine group of the compound having a pyrogallol functional group to condensate and form a carboxyl-amine bond (peptide bond). Accordingly, the pyrogallol functional group may be introduced to the position of the carboxyl group by the EDC / NHS introduction method. In this case, the raw polymer compound used may be any polymer compound having a carboxyl group without limitation, but preferably, carboxymethyl cellulose (CMC, Formula 4), hyaluronic acid (HA, Formula 5), alginate (Alginate, Formula 6).

(Formula 4)

(Formula 5)

(Formula 6)

In addition, an activator may be added to activate the carboxyl functional group of the raw polymer compound, and the activator is preferably 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide (EDC). The EDC is preferably added in a ratio of 1 to 5 times the number of moles relative to the carboxyl functional groups present in the raw polymer compound, more preferably may be added in a ratio of 3 times.

In the manufacturing method according to the present invention, step (b) is a step of adding a compound having a pyrogallol functional group to a raw polymer compound solution, followed by stirring.

The compound having a pyrogallol functional group may include an amino group (-NH ₂ ), and preferably may have a structure of Formula 7 below.

(Formula 7)

The compound having a pyrogallol functional group of the present invention may be a plant-derived compound, and preferably, may be prepared by hydrolyzing plant-derived gallic acid or tannin. The compound having a pyrogallol functional group is preferably added in a ratio of 1 to 5 times the number of moles relative to the carboxyl functional groups present in the raw polymer, and more preferably in a ratio of 4 times. At this time, in order to prevent natural oxidation of the compound having a pyrogallol functional group, it is preferable to adjust the pH of the aqueous solution to 3 to 6, and more preferably to adjust the pH to 5. In addition, in order to prevent natural oxidation of the compound having a pyrogallol functional group, it is preferable to block oxygen in the solvent as much as possible, and it is more preferable to perform the reaction in a nitrogen substitution environment.

In addition, N-hydroxysuccinimide (NHS) may be further added to increase the introduction rate of pyrogallol functional groups. The NHS is preferably added in a ratio of 3 to 7 times the number of moles relative to the carboxyl functional groups present in the polymer compound, and more preferably in a ratio of 5 times.

The reaction time of step (b) is preferably 3 hours to 12 hours, and when EDC is used, it is preferable to react for 5 hours.

In the production method according to the present invention, step (c) is a step of obtaining a polymer compound into which pyrogallol functional groups are introduced by removing unreacted materials. At this time, the step of removing the unreacted material may be a step of removing the unreacted material by using a semipermeable filtration membrane and then freeze drying. After completion of the reaction of step (b), by performing the dialysis using a semi-permeable filtration membrane capable of permeation of molecules having a molecular weight of 3,500 or less, monomolecules not participating in the reaction can be removed. At this time, the solution used for dialysis may be used phosphate buffered saline (Phosphate Buffer Saline, PBS). The dialysis solution is preferably performed by repeating dialysis 2 to 10 times while exchanging the dialysis solution on a 2-10 hour basis, and more preferably, the dialysis solution is performed by repeating 4 to 6 times while exchanging the dialysis solution on the basis of 5 to 7 hours. Can be.

Finally, unreacted monomolecules and ions are removed as much as possible through the dialysis and then freeze-dried to obtain a polymer into which a pyrogallol functional group is introduced.

In the embodiment of the present invention as a result of analyzing the absorbance to confirm the degree of introduction of the polymer of the pyrogallol functional group, the absorbance is achieved in the 275 nm wavelength region of the typical light absorption region of the pyrogallol functional group for the polymer prepared by the above production It was confirmed that through this, 9% to 12% of the carboxyl groups were introduced by being substituted with pyrogallol functional groups (see FIG. 2).

The present invention according to the third aspect also provides a polymer into which a pyrogallol functional group produced by the above method is introduced.

The present invention according to the fourth aspect also provides an electrode material comprising a high molecular compound into which a pyrogallol functional group is introduced.

In addition, the present invention according to the fifth aspect comprises the steps of: (i) dissolving the polymer compound in which the pyrogallol functional group is introduced into distilled water; And (ii) adding a silicon nanoparticle and a conductive compound to the polymer solution into which the pyrogallol functional group is introduced, thereby preparing a silicon electrode material. It provides a method of manufacturing.

Hereinafter, the manufacturing method will be described in detail for each step.

In the manufacturing method according to the present invention, step (i) is a step of dissolving the polymer compound into which the pyrogallol functional group is introduced in distilled water to prepare a polymer solution.

The polymer compound into which the pyrogallol functional group is introduced may preferably have a concentration of 1 to 3% by weight in the solvent, and more preferably 2% by weight. In addition, although the solvent used at this time is preferably using distilled water, as long as it is a solvent capable of dissolving the polymer compound into which the pyrogallol functional group is introduced, other types of solvent may be used as necessary.

In the manufacturing method according to the present invention, step (ii) is a step of preparing an electrode material by adding silicon nanoparticles and a conductive compound to the polymer solution prepared in step (i).

For the polymer solution prepared in the above step, the silicon nanoparticles are preferably added 2 to 6 times the mass of the polymer, and more preferably 3 times the silicon nanoparticles may be added.

In addition, the conductive compound is preferably added 0.5 to 2 times the mass of the polymer with respect to the polymer solution, more preferably a conductive compound of the same mass as the polymer mass may be added. In addition, the conductive compound may include ITO, silver nanowires, silver nanoparticles, carbon compounds, iron, copper, aluminum, gold, silver, nickel or tin, preferably a carbon compound, more preferably carbon nanotubes, Carbon fibers, fullerenes or graphite may be included.

In addition, in step (ii), it is most important to evenly disperse the additive material, and it is preferable to disperse evenly through the ultrasonic generator.

In addition, the present invention according to the sixth aspect provides a silicon secondary battery electrode material using a polymer compound into which a pyrogallol functional group prepared by the above method is introduced as a binder.

In addition, the present invention according to the seventh aspect comprises the steps of: (1) coating the silicon secondary battery electrode material on a copper thin film to produce an electrode; And (2) provides a method for manufacturing a silicon secondary battery electrode comprising the step of cutting the electrode prepared in the step (1) to form a insertable into the battery.

Hereinafter, the manufacturing method will be described in detail for each step.

In the manufacturing method according to the present invention, the step (1) is a step of producing an electrode by applying to the copper thin film using the silicon secondary battery electrode material.

The secondary battery electrode material is evenly applied to the copper thin film. At this time, if the device that can uniformly apply the electrode material to the copper thin film can be used without limitation, the electrode material can be applied, it is preferable to apply using a doctor blade equipment. At the time of application, the initial battery capacity can be adjusted according to the thickness. In the embodiment of the present invention, 0.8 ~ 1.2 mg of the electrode material is applied per unit area (1 mm ² ) during electrode cutting, but is not limited thereto. In addition, the thickness of the copper thin film is preferably 5 ~ 20 ㎛.

The step (2) is a step of producing the electrode form that can be inserted into the battery by cutting the electrode produced in the step (1).

The electrode can be manufactured and inserted according to the shape of the battery to be manufactured. In an embodiment of the present invention, a circular electrode having a diameter of 14 mm was manufactured to fabricate an electrode suitable for a 2032 coin-shaped half cell, but may be processed in various forms according to the size and type of battery used. In particular, since the copper thin film used for the electrode is a material having excellent malleability and ductility, it can be easily processed to produce an electrode.

The present invention according to the eighth aspect also provides a silicon secondary battery electrode produced by the above method.

In one experimental example of the present invention, to determine the battery life improvement ability of a silicon secondary battery using a polymer incorporating a pyrogallol functional group as a binder, a 2032 coin-type half cell was manufactured to measure the unit discharge capacity according to the charge and discharge cycle. It was. As a result, it was confirmed that the polymer having the pyrogallol functional group introduced therein had a capacity of 1.3 to 2.3 times higher than that of the general binder without the pyrogallol functional group (FIG. 3 (A) and (B)). Reference).

In addition, in order to confirm the strength enhancement of the silicon electrode using a polymer incorporating pyrogallol functional group as a binder, a 2032 coin-type half-cell was fabricated to confirm the lifespan capacity according to the increase of the charging speed. As a result, it was confirmed that the filling capacity retention capacity of the binder was improved in the polymer into which the pyrogallol functional group was introduced (see FIG. 3 (C)).

In another experimental example of the present invention, in order to visually demonstrate the strength enhancement of the silicon electrode using a pyrogallol functional group as a binder, a 2032 coin-type half cell was fabricated with the electrode, followed by five charge and discharge cycles. The separation was carried out, and the change in the surface form of the silicon electrode was confirmed by an electron scanning microscope. As a result, no crack was observed only in the electrode using the pyrogallol functional group polymer as a binder, and visually confirmed that the strength of the electrode itself was improved due to the polymer incorporating the pyrogallol functional group (see FIG. 4).

In another experimental example of the present invention, in order to demonstrate that the interaction between the polymer used as the binder and the negative electrode material increases due to the introduction of the pyrogallol functional group, the mixture of the polymer and the silicon nanoparticle mixture is increased while increasing the mixing ratio of the silicon nanoparticles. Infrared absorption spectrum was confirmed. As a result, as the proportion of silicon nanoparticles increased, the absorption at 3400 cm ^-1 due to the vibration of the oxygen-hydrogen bond of the hydroxy group possessed by the pyrogallol functional group introduced into the polymer decreased. It was possible to indirectly prove that the hydroxy group of interacts with the silicon particles (see FIG. 5).

In another experimental example of the present invention, to demonstrate the covalent bond generation and gelation by self-oxidation of a silicon electrode using a pyrogallol functional group as a binder, a concentration of 2% by mass, which is the same concentration as that of the polymer used in electrode production, was demonstrated. The rheological properties of the polymer solution were measured with a rheometer after time of solution preparation. As a result, the elastic modulus of the solution increases over time, and the width of the elastic modulus becomes larger than that of the viscous modulus, resulting in a gelled material through the viscoelastic material (see FIG. 6).

In another experimental example of the present invention, in order to visually check the change in the shape of the polymer when the gelation proceeds by the pyrogallol functional group derivatives as a binder of the electrode, the electrode material is manufactured by the same method as the above manufacturing method. The shape of the electrode material was observed with a scanning electron microscope. As a result, as the time passes, a large number of bonds due to oxidation were generated in the polymer itself, and it was confirmed that the bonds such as polymer-polymer or polymer-silicon particles were made more densely in a net form. (See FIG. 7).

In another experimental example of the present invention, in order to demonstrate a covalent bond generation mechanism by self-oxidation of a silicon electrode using a pyrogallol functional group-introduced polymer as a binder, a model group similar in form to the polymer in which the pyrogallol functional group is introduced Using the propylgallate molecule as a molecule, retention time according to the time change after the preparation of the solution was confirmed by high performance liquid chromatography, and as a result, it was confirmed that the molecular weight was increased by covalent bond generation (FIG. 8). Reference). It was also confirmed by mass spectrometry that intermolecular dimers formed due to oxidation by simple air exposure in solution (see FIG. 9). Through these comprehensive results, the pyrogalol-derived polymer can demonstrate a series of mechanisms that enhance the overall cohesion by covalent bonds through the oxidation reaction between two pyrogallol molecules in a polymer or between two pyrogallol molecules between polymers. Could.

Accordingly, the present invention relates to a method of improving the overall binding force of a battery electrode by introducing various cross-links to the polymer binder by introducing a pyrogallol functional group, which is a core functional group of an antioxidant derivative of a plant, into a polymer compound. In addition, by crosslinking between polymers or within polymers through covalent bonds by self-oxidation of pyrogallol functional groups, a strong structure in the form of a net is formed on the battery electrode, thereby making it resistant to deformation of the electrode. It is about. As the pyrogalol functional group is introduced into the polymer, the above-mentioned various direct and indirect interconnection capacities are imparted in the cell, resulting in not only a strong structural characteristic but also a stable structure in spite of the deformation of the structure. Self-healing can also be gained with return. Unlike the polymer binders that have been proposed in the past, by introducing pyrogallol functional groups, excellent performance of silicon-based negative electrode materials can be expected for polymers. Thus, unlike conventional polymer binders using only limited polymers, any polymer Flexibility to choose and use a binder.

In addition, the above-mentioned reaction method introduced a pyrogallol amine functional group having an amine (-NH ₂ ) to the polymer having a carboxyl group (-COOH) by introducing an EDC / NHC introduction method, but in addition to the functional group described above, Since there is a method of introducing a single molecule into the polymer using a variety of two functional groups, the type of the polymer is not limited to the polymer having a carboxyl functional group shown in this embodiment. It is considered that pyrogallol can be used as a binder of pyrogallol introduced polymer cotton silicon negative electrode material in which functional groups of 5% to 10% are substituted. In conclusion, the polymer in which the pyrogallol functional group is introduced may be used as a binder of the silicon-based next-generation secondary battery.

The following Examples and Experimental Examples are only illustrative of the present invention, and the content of the present invention is not limited to the following Examples and Experimental Examples.

EXAMPLES Preparation of Polymers Incorporating Pyrogallol Functional Groups

The polymer in which the pyrogallol functional group is introduced according to the present invention includes a pyrogallol derivative having a amine group (-NH ₂ ) of formula (7) in the polymer having any one of the following formulas (4) to (carboxy) (-COOH): The molecule, pyrogallol amine, was prepared by the introduction of EDC / NHS.

(Formula 4)

(Formula 5)

(Formula 6)

(Formula 7)

After dissolving the polymer of any one of Formulas 4 to 6, carboxymethyl cellulose (CMC), hyaluronic acid (HA), alginate (Alginate) in 10 ml distilled water at 0.5% by weight, EDC and NHS are respectively 3 times and 5 times the number of moles of carboxyl groups were added. After the addition of EDC / NHS, the pH of the solution was adjusted to 1 M HCl and 1 M NaOH solution, and then the pyrogallol amine compound of Formula 7 was compared to the mole number of the polymer carboxyl group of any one of Formulas 4 to 6. Two times the amount was added. The pH was adjusted to 5 again. At this time, when the pH value exceeds 6, the oxidation of pyrogallol amine itself proceeds rapidly, so it may not be introduced into the polymer. The progress of all the reactions described above was carried out in a nitrogen-blocked nitrogen environment. The reaction was carried out while stirring at room temperature for 5 hours. After completion of the reaction, the reaction solution was placed in a semi-permeable membrane capable of transmitting only a single molecule having a molecular weight of less than 3,500 to remove molecules that did not participate in the reaction. In order to prevent the precipitation of the polymer, initial dialysis was performed by replacing the solution every 6 hours with PBS (150 mM NaCl) solution, followed by 3 times with 150 mM NaCl solution and finally 4 hours with distilled water. It was. After dialysis, the polymer was rapidly frozen through liquid nitrogen and vacuum-freeze dried at -70 ° C. for 1 week.

Experimental Example 1 Characterization of Polymers Incorporated with Pyrogallol Functional

In order to check whether the pyrogallol functional group is stably introduced into the polymer compound prepared in <Example 1>, absorption characteristics were analyzed by an ultraviolet / visible spectrometer (UV / Vis spectroscope, HP8543, Hewlett-Packard, USA).

Specifically, 150 μl of a 1 mg / ml aqueous polymer solution is placed in a spectrometer cuvette and the absorbance in the 275 nm wavelength range is measured. The polymer compound into which the pyrogallol functional group is introduced has an absorption at 275 nm, which is the absorption wavelength of pyrogallol. When the pyrogallol amine is prepared in an aqueous solution having various concentrations and the absorbance is measured to make an appropriate curve, when the absorbance value of the 275 nm wavelength region of the polymer solution is known, the substitution ratio of the pyrogallol functional group introduced into the polymer compound can be calculated. have. In the case of the polymer compound subjected to the reaction as shown in the above example, the absorption graph is shown as shown in FIG. 2, and it was confirmed that all of them were absorbed at 275 nm wavelength. It became.

< Example  2> Fabrication of silicon electrode using high molecular compound with pyrogallol functional group as binder and fabrication of 2032 coin-type lithium-silicon half cell

The polymer compound into which the pyrogallol functional group according to <Experimental Example 1> is introduced has a structure of any one of the following Chemical Formulas 1 to 3.

(Formula 1)

(Formula 2)

 (Formula 3)

A polymer corresponding to any one of Formulas 1 to 3, carboxymethylcellulose (CMC-GA) in which pyrogallol functional groups are introduced, alginate (Alg-GA) incorporating pyrogallol functional groups, and hyaluronic acid incorporating pyrogallol functional groups (HA-GA) was dissolved in distilled water at 2% by weight, respectively, to prepare 1 ml. Each aqueous polymer solution was added to the mortar, and 6 wt% of silicon nanoparticles having a particle size of less than 100 nm were added and mixed well with a pestle. After the addition of 2% by weight of the conductive conductive material of the carbon material was mixed well with a pestle. The silicon anode material slurry thus prepared was deposited on a copper thin film of 8 cm x 20 cm x 19 μm. It was applied thinly using blade equipment. At this time, the coated electrode material was a circular electrode having a diameter of 14 mm so that the mass of the electrode material did not exceed 1 mg at the time of cutting. The electrode prepared by coating on the copper thin film was dried by high-temperature vacuum drying at 70 ℃ to remove moisture. The dried electrode was cut into a circular electrode using a 14 mm diameter stamp. The manufactured negative electrode was used to fabricate a 2032 coin-shaped half cell together with lithium metal.

< Experimental Example  3> Analysis of Lifespan Characteristics of Lithium-Silicone Half Cell Using Polymers with Pyrogallol Functional as Binder

Using the 2032 coin-shaped half-cell manufactured in <Example 2> was performed to analyze the life retention characteristics according to the charge and discharge cycle.

Specifically, in addition to the lithium-silicon half battery using the polymer binder incorporating the pyrogallol functional group produced in Example 2, using the general polymer binder half cell produced in the same manner as in Example 2 It was confirmed by the charge-discharge cycle iteration whether the life-span characteristics improved with or without pyrogallol. The charge and discharge rate was set to 3500 mAh / g of the initial unit charge capacity of the silicon-based negative electrode material, a current of 3500 mA / g was applied to each half cell to allow a buffer (1 C rate) within 1 hour. After 300 cycles of charging and discharging, the capacity retention rate of the battery was confirmed. As a result, the polymer compound in which pyrogallol functional group was introduced compared to the conventional polymer was improved by 1.3 to 2.3 times. It was confirmed by the ratio of the unit charge rate (Fig. 3 (a), (b)) In addition, the life retention characteristics of the battery according to the increase in the charge and discharge rate was confirmed through the unit charge retention rate, the introduction of the pyrogallol functional group of the binder It was confirmed whether or not battery life characteristics were improved. At an initial current of about 220 mA / g (1/16 C rate), the charging rate is increased by two multiples every five charge-discharge cycles, increasing to 3500 mA / g (1 C rate), then decreasing to 220 mA / g rate As a result of confirming the preservation rate of the unit charge capacity of the battery, it was confirmed that the preservation rate of the battery using the polymer compound into which the pyrogallol functional group was introduced as the binder (FIG. 3 (C)).

< Experimental Example  4> Confirmation of structure maintenance of lithium-silicon half cell using high molecular compound with pyrogallol functional group as binder

Using the 2032 coin-shaped half-cell produced in <Example 2> it was confirmed that the structure of the battery according to the charge and discharge cycle.

Specifically, the 2032 coin-shaped half-cell manufactured in <Example 2> was charged and discharged at a rate of 3500 mA / g in the same manner as the charge / discharge circulation method presented for the analysis of lifespan maintenance in <Experiment 3>. After performing the charge / discharge cycles, the structural change of the electrode was visually analyzed and the improvement of structure retention ability was confirmed by the introduction of pyrogallol functional group. The half cell that has been charged and discharged five times is separated in a glove box of an argon environment, and a negative electrode is obtained, followed by drying in a glove box to dry the electrolyte. The resulting electrode was thin-coated with platinum / palladium sputter for 45 seconds and visually confirmed the structural change of the electrode through a scanning electron microscope (Inspect F50, FEI Co., USA). According to FIG. 4, it can be seen that even through five charge and discharge cycles, a large number of micro cracks are generated in a silicon anode electrode manufactured using a general polymer binder. It was confirmed that the CMC polymer, which is proposed as a binder candidate of the existing silicon anode material, also caused microcracks of the electrode by five charge and discharge cycles.In the case of the HA polymer used as the experimental group, the degree of cracking was more severe than that of CMC. You can see that most of the electrodes are damaged and separated. The stability of the initial structure is very important because the electrode has a stable by-product film (SEI Layer) formed at the beginning of the circulation to stabilize the overall structure of the electrode and maintain a constant charge / discharge capacity thereafter. All HA polymers can be seen that the shape maintenance of the electrode by the initial charge-discharge cycle is very unstable. On the other hand, in the case of an electrode using a polymer having a pyrogallol functional group as a binder, it was confirmed that the structure of the electrode was very stably maintained without micro cracking even in five charge and discharge cycles. As a result, it was confirmed that the pyrogallol-introduced polymer has a stable structure retention characteristic in the initial charge-discharge cycle compared to the general polymer, thereby maintaining a stable charge capacity even in the charge-discharge cycle.

< Experimental Example  5> Identification of various interaction forces and self-recovery ability related to battery life maintenance characteristics of pyrogallol functional group polymer binder

Infrared spectroscopy, high performance liquid chromatography, mass to confirm that the polymer introduced with the pyrogallol functional group prepared in Example 1 is improved in the overall structural performance of the battery by introducing a variety of interaction forces compared to the general polymer Experiments such as analytical methods and rheological analyzes were performed, and the structure was analyzed by scanning electron microscopy to demonstrate various interaction forces of the polymer binders exhibited by pyrogallol functional groups.

Specifically, in order to confirm the structural performance of the electrode is improved because the polymer in which the pyrogallol functional group is introduced is used as the binder of the silicon negative electrode material, the interaction between the silicon nanoparticles and the pyrogallol working period, which occupy the majority of the silicon negative electrode material, is confirmed. Infrared spectrophotometry was confirmed by infrared spectroscopy (Agilent technologies, Cary 600 series, USA). According to FIG. 5, the polymer having pyrogallol functional groups exhibits a very high absorption at 3400 cm ⁻¹ , which is an absorption region due to the vibration of the oxygen-hydrogen bond of the hydroxyl group (—OH) possessed by the pyrogallol functional groups. However, In the case of a material in which the pyrogallol functional group-introducing polymer and the silicon nanoparticles are mixed in a mass ratio of 1: 1 and 2: 1, respectively, the absorbance of the corresponding light absorption region is significantly reduced. This shows that the absorption of hydroxy groups by indirect cross-linking with silicon nanoparticles reduced their absorption. This tendency is that the polymers into which pyrogallol functional groups are introduced have a lower absorption as compared to silicon particles. Prove that through. Through this, it was proved that pyrogallol functional group introducing polymer has an indirect interaction force with silicon of the silicon electrode, thereby indirectly confirming that the overall structural stability of the entire electrode was improved.

In addition, in addition to the indirect interaction force of the silicon-pyrogallol functional period demonstrated in FIG. 5 below, the natural oxidation ability of the pyrogallol functional group demonstrates that crosslinking is formed through covalent bonding, which is a direct interaction between the pyrogallol functional groups. It was. First, a propyl gallate monomolecular solution having a pyrogallol functional group is prepared, and after 48 hours of exposure to air, the solution before exposure is subjected to retention time using high performance liquid chromatography (Agilent technologies, Agilent 1200, USA). The molecular weight corresponding to the retention time was compared. As a result, the molecule exposed to air for 48 hours was found to have a higher molecular weight (FIG. 8). This shows that the pyrogallol functional group-introduced polymer is naturally oxidized by oxygen in the air, thereby forming a covalent bond between the pyrogallol functional groups to increase the overall molecular weight. High Performance Liquid Chromatography with Mass Spectrometry after Producing a Solution of Gallate Monomolecules in the same manner as in the experiment of FIG. 8 to clearly demonstrate that pyrogallol functional groups form bonds by natural oxidation such as dimer formation (Agilent technologies, Agilent 1200, USA). As a result, a substance having the same molecular weight as the dimer molecular weight of the monomolecule was detected in the monomolecular solution after 48 hours of elapsed time (lower part in FIG. 9). This demonstrates that pyrogallol functional groups directly cross-link in the air to form covalent bonds by natural oxidation. Through these results, it is possible to indirectly prove that the pyrogallol functional group-introducing polymer forms covalent bonds between the pyrogallol functional groups by natural oxidation even in the silicon electrode, which contributes to strengthening the overall structure of the electrode by acting as a crosslinking between the polymers. have. In order to confirm that the pyrogallol functional group-introducing polymer improves the structural properties of the silicon electrode by crosslinking of the pyrogallol functional group, the silicon negative electrode material slurry prepared in the same manner as in <Example 2> was immediately or 48 hours after preparation of the slurry. After exposure in the air and freeze-drying, structural changes were confirmed by scanning electron microscopy. As a result, it was confirmed that the overall structure of the electrode was changed into a net shape after 48 hours of air exposure (FIG. 7). This structural change is due to the formation of crosslinks between polymers due to the covalent bond formation of the pyrogallol functional group described above, and visually proved that the structural properties of the electrode were effectively improved.

In addition to the structural characteristics described above, when analyzed based on the image of the scanning electron microscope (Inspect F50, FEI Co., USA) of FIG. 7, the pyrogallol functional group-introduced polymer prepared in the same manner as in <Example 1> When prepared as an aqueous solution, the aqueous solution can be said to have the characteristics of a gel. Through such gelation, the pyrogallol functional group-introducing polymer body can not only improve the overall structural performance of the silicon negative electrode binder, but also provide self-healing ability, which is one of the characteristics of the gel, to extend the life of the electrode. It can contribute greatly. In order to confirm that the pyrogallol functional group-introduced polymer aqueous solution has gel properties, the pyrogallol functional group-introduced macromolecular solution prepared by using the pyrogallol functional group-introduced polymer body as a binder in 2 wt% of the aqueous solution was prepared by rheology Assay was performed.

Specifically, 300 μl of the aqueous solution used in Example 2 was placed on a sample holder of a Rheometer (Bohlin Advanced Rheometer, Malvern Instruments, UK), followed by using a flat plate of 20 mm thickness using 0.1- The elastic modulus (G ') and the viscous modulus (G ") were measured for the degree of deformation of the material by applying a constant stress of 100 Pa at a frequency of 10 rad / sec.

<Equation 1>

In Equation 1,

α is the shear stress on the material;

γ 0 is the maximum amplitude of the shear strain exhibited by the deformation of the material;

G 'is an elastic modulus;

G '' is the viscosity coefficient;

ω is the frequency; And t is time.

According to FIG. 6, the prepared aqueous solution initially has a viscoelastic material having a medium physical property between the liquid and the gel, but as the production time passes, the elastic modulus (G ′) gradually exceeds the viscosity modulus (G ″). Based on the direct and indirect interaction force by pyrogallol, which was proved through the above description, the gelation of pyrogallol aqueous solution also has a complex series of interaction forces of pyrogallol functional groups. In conclusion, through the experiments described above, the polymer in which the pyrogallol functional group is introduced is inserted into the electrode binder in the form of a gel by natural oxidation in the silicon anode, thereby inducing complex interaction between the materials inside the electrode. To improve the life characteristics of the electrode by forming a strong structure in the form of a net with self-healing ability. They were able to demonstrate the.

< Experimental Example  3> Hydroxyl groups  Effect

As described above, the pyrogallol functional group has a structure in which three hydroxyl groups are bonded to a phenyl group. On the other hand, the catechol functional group has two hydroxyl groups in the phenyl group, and in the present experimental example, the same catechol-derived polymer having the two hydroxyl groups as in Chemical Formula 7 was used as the comparative example.

10 and 11 are air exposure natural oxidation capacity test results of the catechol-derived polymer binder and the pyrogallol-derived polymer binder, respectively.

Referring to FIGS. 10 and 11, the catechol-derived polymer and the pyrogallol-derived polymer (2 wt%) such as the concentration of the polymer to be mixed when preparing the electrode slurry are exposed to air in an aqueous solution for 120 hours to increase the natural oxidation ability of the air. Compared.

In FIG. 10, since the catechol-derived polymer has almost no natural oxidation ability due to air exposure, physical properties of the catechol-derived polymer are hardly observed even after 120 hours of air exposure. It can be seen that it naturally oxidizes and changes to gel form after 120 hours. This can be confirmed by a simple container inversion test as shown in FIGS. 10 and 11.

Therefore, it can be seen that the pyrogallol-derived polymer of the binder according to the present invention has excellent gelling ability as a binder by natural oxidation in contact with air as a binder.

12 and 13 are results of measurement of the change in rheological properties by air exposure natural oxidation of catechol-derived polymer and pyrogallol-derived polymer, respectively.

Referring to FIGS. 12 and 13, the catechol-derived polymer and the pyrogallol-derived polymer (2 wt%) such as the concentration of the polymer to be mixed when preparing the electrode slurry are exposed to air in an aqueous solution for 120 hours to generate physical properties by natural oxidation. The change is observed through the rheology system. The catechol-derived polymer has little natural oxidation ability due to air exposure, and thus, even after 120 hours of air exposure, the change in viscosity / elasticity coefficient before and after exposure was not observed so that the overall physical property change was hardly achieved. On the other hand, in the case of pyrogallol-derived polymers, the viscoelastic material (G “) was higher than the elastic modulus (G ') in the overall frequency range immediately before the mixing due to the ability to naturally oxidize by air exposure when mixing the aqueous solution. It can be seen that after 120 hours in physical properties, the physical properties change in a gel form with a higher modulus of elasticity (G ') than the viscosity coefficient (G ").

From the above experimental results, it can be seen that the number of hydroxyl groups bound to the phenyl group must be three to have gelation ability through natural oxidation, and this means that the pyrogallol functional group according to the present invention, that is, three hydroxyl groups in the phenyl group It is suggested that the bound functional groups are very important as binders.

As described above in detail specific parts of the present invention, it will be apparent to those skilled in the art that these specific descriptions are merely preferred embodiments, and thus the scope of the present invention is not limited thereto. will be. Thus, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (20)

In the binder compound for electrodes introduced pyrogallol functional group,
The electrode binder compound is a binder compound for electrodes having a structure of any one of the following formula (1) to (3).
(Formula 1)

(Formula 2)

(Formula 3)

delete (a) mixing the raw polymer compound with a solvent to dissolve it;
(b) adding a compound having a pyrogallol functional group to the raw polymer compound solution and then stirring to introduce the pyrogallol functional group into the raw polymer compound; And
(c) removing the unreacted material to obtain a polymer compound into which a pyrogallol functional group is introduced;
A method for producing a binder compound for an electrode, wherein the pyrogallol functional group of claim 1 is introduced. The method of claim 3,
The raw polymer compound is a method for producing a binder compound for an electrode containing a carboxyl group (-COOH). The method of claim 4, wherein
The raw polymer compound is a method for producing a binder compound for an electrode having a structure of any one of formulas (4) to (6).
(Formula 4)

(Formula 5)

(Formula 6)

The method of claim 3,
The compound having a pyrogallol functional group is a method of producing a binder compound for electrodes that is a plant-derived compound. The method of claim 3,
The compound having a pyrogallol functional group is a method for producing a binder compound for an electrode containing an amino group (-NH ₂ ). The method of claim 7, wherein
The compound having a pyrogallol functional group is a method for producing a binder compound for an electrode having a structure of formula (7).
(Formula 7)

The method of claim 3,
Step (a) is a method for producing a binder compound for an electrode comprising the addition of an active agent. The method of claim 9,
The active agent is a method for producing a binder compound for electrodes comprising 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide (EDC). The method of claim 3,
Wherein (c) the step of removing the unreacted material, a method of producing a binder compound for an electrode which is a step of removing the unreacted material using a semi-permeable filter membrane, and then lyophilized. delete delete An electrode material comprising a binder compound for electrodes into which the pyrogallol functional group of claim 1 is introduced. (i) dissolving the binder compound for electrodes into which the pyrogallol functional group of claim 1 is introduced, in distilled water; And
(ii) preparing a silicon electrode material by adding silicon nanoparticles and a conductive compound to the binder compound solution for electrodes into which the pyrogallol functional group is introduced;
Method for producing a silicon secondary battery electrode material using a binder compound for electrodes introduced pyrogalol functional group comprising a. The method of claim 15,
The conductive compound is ITO, silver nanowires, silver nanoparticles, carbon compounds, iron, copper, aluminum, gold, silver, nickel or tin containing method of manufacturing a silicon secondary battery electrode material. A silicon secondary battery electrode material using a binder compound for an electrode having a pyrogallol functional group produced by the method of claim 15 introduced therein as a binder. (1) preparing an electrode by applying the silicon secondary battery electrode material of claim 17 to a copper thin film; And
(2) cutting the electrode prepared in step (1) to produce a battery insertable form;
Method of manufacturing a silicon secondary battery electrode comprising a. The method of claim 18,
The copper thin film is a method of manufacturing a silicon secondary battery electrode having a thickness of 5 ~ 20 ㎛. A silicon secondary battery electrode prepared by the method of claim 18.

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