KR20180112928A - Electrode, secondary battery, and method thereof - Google Patents

Abstract

Provided is a flexible secondary battery electrode. The flexible secondary battery electrode is made with slurry containing an electrode active material, polyurethane as a binder, and a conductive agent comprising carbon. The conductive agent may include carbon nanotubes. A method for production the secondary battery electrode comprises the following steps: preparing the slurry containing the electrode active material, polyurethane as the binder, and the conductive agent containing carbon; casting the slurry on a substrate; and removing the cast slurry from the substrate.

Description

TECHNICAL FIELD [0001] The present invention relates to a secondary battery electrode, a battery including the secondary battery electrode,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery electrode field, and more particularly, to a secondary battery electrode which is flexible and excellent in discharge capacity and cycle stability, a battery including the same, and a method of manufacturing the same.

Recently, lithium-ion batteries (LIBs) have been expanding their markets in a variety of fields, including small mobile IT devices such as cellular phones and notebook computers, electric vehicle power, and energy storage systems. As part of this trend, there is a growing demand for flexible lithium-ion batteries that can meet the requirements of various designs and power sources for portable electronic devices, including roll-up displays and wearable devices. Furthermore, active radio frequency identification tags and IC smart cards also require batteries that are flexible or at least bendable in practical use.

Generally, a lithium-ion battery is composed of a cathode, an anode, an electrolyte between these electrodes, and a separator. Conventional electrodes include an active material, a conductive agent, a binder, and a metal foil as a current collector. Conventional electrodes based on these metal foils are not suitable for use as a flexible lithium ion battery because the active material can be separated or cracked repeatedly during bending or folding, .

For lithium-ion batteries, there are several reports of free-standing materials made from carbon nanotubes (CNTs). A very flexible and conductive CNT paper electrode was fabricated using filtration in a pressurized nitrogen atmosphere. These CNT paper electrodes showed better capacity and cycle stability than conventional CNT electrodes and showed that they are suitable for flexible lithium-ion electrodes. Ben-double cellulose paper electrodes containing CNTs for supercapacitors and batteries have also been proposed and they have shown that the flexibility of the device can be greatly improved using CNT composites. However, the connection between the active materials may be broken during repeated bending or folding. Thus, there is a need for a softer and more flexible material to implement a more rigid and reliable flexible battery that is substantially bendable or taut.

Korean Patent Publication No. 10-2017-0024751

The present invention provides a flexible secondary battery electrode as a freestanding electrode from which a metal current collector is excluded.

The present invention provides a method of manufacturing the above-described improved flexible secondary battery electrode.

The present invention also provides a secondary battery comprising the above-described improved flexible electrode.

The present invention provides a flexible secondary battery electrode comprising: an electrode active material; Polyurethane as a binder; And a conductive agent containing carbon.

Preferably, the polyurethane may comprise 5 to 25 wt%, more preferably 11.5 wt% of the polyurethane.

The conductive agent may include 10 to 12.4 wt%, preferably 50% of carbon black and carbon nanotubes.

The electrode active material may include lithium, cobalt, and oxygen.

The present invention provides a method of making a flexible electrode comprising the steps of: (i) preparing a slurry comprising an electrode active material, a polyurethane as a binder, and a conductive agent comprising carbon; (Ii) casting the slurry onto a substrate; And (iii) removing the cast slurry from the substrate.

And drying the cast slurry before the desorption of step (iii).

The present invention also provides a flexible secondary battery including a freestanding electrode from which a metal current collector is excluded.

According to the present invention, an electrode for a flexible secondary battery is provided. This makes it possible to realize a free standing electrode in a relatively small amount by employing polyurethane as a binder. By properly adding carbon nanotubes in a slurry employing polyurethane as a binder, mechanical strength can be improved while obtaining a suitable electronic conductivity. In addition, a free standing electrode for a lithium ion battery can be provided by a simple method of casting the electrode onto a glass substrate and peeling.

1 is a schematic view of a flexible secondary battery electrode according to a preferred embodiment of the present invention.
2 is a graph showing the peel strength of a metal-based electrode employing polyurethane and PVDF as a binder.
3A is a graph showing the initial charge / discharge curves of a metal-based electrode employing polyurethane and a PVDF binder.
Figure 3b shows the rate capability of metal-based electrodes employing polyurethane and PVDF binders.
Figures 3c and 3d are graphs illustrating the stability of metal-based electrodes employing polyurethane and PVDF binders.
FIG. 4A is a view showing a manufacturing process of a free standing electrode according to Comparative Example 2. FIG.
4B is a view illustrating a process of manufacturing a free standing electrode according to an embodiment of the present invention.
5A to 5C are SEM images of the free standing electrode according to the first embodiment of the present invention.
5D to 5F are SEM images of the free standing electrode according to Comparative Example 1. FIG.
6A shows a stress-strain curve of a free standing electrode according to Example 1 and Comparative Example 1 of the present invention.
6B shows the electronic conductivity of the free standing electrode according to Example 1 and Comparative Example 1 of the present invention.
7A and 7B are graphs showing electrochemical characteristics of the free standing electrode of Example 1 and Comparative Example 1 of the present invention.
7C is a graph showing the cycling stability of the free standing electrode according to Example 1 and Comparative Example 1 of the present invention.
8A shows the initial discharge capacities of the free standing electrodes of Examples 1 to 4 of the present invention.
8B is a graph showing discharge capacities at various current densities of the free standing electrodes according to Examples 1 to 4 of the present invention.
8C is a graph showing the cycle stability of the free standing electrode according to Examples 1 to 4 of the present invention.
FIG. 9A is a view showing an illumination sample manufactured by including a free standing electrode according to Embodiment 1 of the present invention. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

First, the present invention provides a free standing electrode excluding a metal current collector. To this end, an electrode active material, a polyurethane as a binder, and a slurry containing CNT as a conductive agent are used. When polyurethane and CNT are contained in an appropriate ratio, they have desirable mechanical properties as well as favorable electrochemical properties with flexible and mechanical strength. In addition, the production of such an electrode can be realized by a simple process of casting the slurry on a glass substrate and then desorbing it.

Polyurethane (PU) has been reported to have properties suitable for use in gel polymer electrolytes (GPE), binders, and separators, which are attributed to the unique chemical and polymeric structure of the polyurethane do. The polyurethane has a two-phase microstructure of a hard segment and a soft segment. The rigid domain imparts mechanical strength to the polyurethane by hydrogen bonding at the end of the urethane group. On the contrary, the linear soft segment allows the polyurethane to be flexible and stretchable in the soft domain.

Preferred embodiments of the present invention will be described with reference to the drawings.

1 is a schematic view of a flexible secondary battery electrode according to a preferred embodiment of the present invention.

The electrode for a flexible secondary battery of the present invention includes an electrode active material, a polyurethane as a binder, and a conductive agent containing carbon. A preferred embodiment is a free standing electrode that does not include a metal-based current collector.

The electrode active material may include, for example, lithium, cobalt, and oxygen. That is, the flexible secondary battery electrode according to the preferred embodiment of the present invention may be an electrode for a lithium ion battery.

The polyurethane is included as a binder, preferably 5 to 25 wt%. When the content of the polyurethane is less than 5 wt%, the free standing electrode is not realized. When the content exceeds 25 wt%, the tensile strength is increased but the electrical conductivity is remarkably decreased. More preferably, 11.5 wt% of the polyurethane may be included.

The conductive agent may include 2 to 30 wt%, and preferably 10 to 12.4 wt%. In this case, carbon black and carbon nanotubes may preferably be contained in an amount of 50%.

The method for manufacturing a flexible secondary battery electrode of the present invention comprises the steps of (i) preparing a slurry containing an electrode active material, a polyurethane as a binder, and a conductive agent containing carbon, and (ii) Casting the cast slurry on a substrate; and (iii) desorbing the cast slurry from the substrate. And drying the cast slurry prior to the desorption of step (iii).

The slurry described above is slurried by ball milling the mixture with an electrode active material (LCO), a conductive agent and a polyurethane in a composition of 77: 11.5: 11.5 (wt%) in THF (tetrahydrofuran) for 24 hours. As the conductive agent, for example, a mixture of carbon black and carbon nanotubes can be used.

The prepared slurry is cast on, for example, a glass substrate and dried for about 30 minutes, after which the cast film is removed from the glass substrate to obtain a free standing electrode.

As shown in FIG. 1, the prepared free standing electrode of the present invention has uniformly distributed polyurethane and multi-walled carbon nanotubes (MWNT), and an empty space contains an electrode active material (LCO) and carbon black P).

Ⅰ. Possibility of polyurethane as electrode binder

(1) Preparation of metal-based electrode using polyurethane and PVDF binder

To determine whether the polyurethane was suitable as a binder, metal-based electrodes were prepared employing polyurethane and PVDF as binders, respectively. The composition of each slurry was 90: 5: 5 wt% of an electrode active material (LCO): carbon black (super P): binder (polyurethane or PVDF). The slurry was cast on an aluminum foil using a doctor blade, and the amount of the electrode active material on the foil was 9.0 mg / cm < ^{2 &} gt ;.

(2) Mechanical analysis of metal-based electrodes employing polyurethane and PVDF binder

A peel strength test was performed on the metal-based electrodes using the test equipment (instron 5960) to measure the adhesion / cohesion. The electrode was cut to 20 cm (L) x 2.5 cm (W) to prepare a test piece, and a 3M tape was attached to the electrode. The tape was pulled at a constant speed of 10 mm / min to measure the average load.

2 is a graph showing the peel strength of a metal-based electrode employing polyurethane and PVDF as a binder. As can be seen from the figure, the polyurethane (PU) binder exhibited adhesive strength as high as about 0.5 N higher than PVDF. Thus, having a high PU adhesion property than PVDF means that it can be used as a polymer binder for a lithium ion battery.

(3) Electrochemical properties of metal-based electrodes employing polyurethane and PVDF binder

3A is a graph showing the initial charge / discharge curves of a metal-based electrode employing polyurethane and a PVDF binder. The electrode (Al-PVDF) made of PVDF binder and the electrode (Al-PU) made of polyurethane binder showed almost the same charge / discharge profile. The initial charge and discharge capacities of the Al-PVDF electrode were 159.6 mAh / g and 153.6 mAh / g, respectively. The initial charge and discharge capacities of the Al-PU electrode were 157.7 mAh / g and 153.6 mAh / g.

Figure 3b shows the rate capability of metal-based electrodes employing polyurethane and PVDF binders. The speed characteristics were measured at various current densities from 0.1 to 5 占 폚. At high C-rate (discharge rate), the two metal-based electrodes did not exhibit a noticeable capacity difference and showed a difference in discharge capacity of only 1.1% at 5 ° C.

Figures 3c and 3d are graphs illustrating the stability of metal-based electrodes employing polyurethane and PVDF binders.

Cycling stability of metal-based electrodes was tested at constant current density (0.5 C charge / 1.0 C discharge) at ambient temperature and high temperature (45 캜). As shown in Figures 3c and 3d, even after 100 cycles, the electrodes showed no noticeable difference in cycle stability. At the ambient temperature, the discharge capacity retention rates (relative to the first discharge capacity) of the Al-PVDF and Al-PU electrodes were 98.1 and 98.3%, respectively. Similarly, at elevated temperatures of 45 ° C, the Al-PVDF and Al-PU electrodes showed 94.5% and 95.4%, respectively, showing no noticeable difference. The above results show that polyurethane (PU) is not a problem for use as a binder for lithium ion batteries, and because of its unique softness and flexibility, it can be one of the most promising candidates for a flexible lithium ion battery binder. Respectively.

Ⅱ. Free standing electrode

(1) Preparation of free standing electrode according to the present invention

To prepare the free standing electrode according to the present invention, a mixture having an electrode active material (LCO), a conductive agent, and a polyurethane as a binder in the compositions of Examples 1 to 4 as shown in Table 1 was dissolved in THF (tetrahydrofuran) ≪ / RTI > for 24 hours to produce a slurry. A mixture of carbon black (Super P) and multi-walled carbon nanotube (MWNT) nano solution of the same weight was used as a conductive agent. The slurry was cast on a glass substrate using a doctor blade and dried at ambient temperature for 30 minutes. Next, the cast film was peeled from the glass substrate to obtain a free standing electrode.

1 is a view schematically showing a free standing electrode of the present invention. As shown in the drawing, the carbon nanotube (MWNT) and the polyurethane are uniformly distributed and the void space is filled with the electrode active material (LCO) and the carbon black.

(2) Preparation of free standing electrode of Comparative Example 1

In order to investigate the effect of addition of carbon nanotubes (MWNT), an electrode active material (LCO) excluding MWNT, carbon black (Super P) and polyurethane (PU) as a conductive agent were mixed in a ratio of 77: 11.5: ) Was prepared. The free standing electrode of Comparative Example 1 was prepared.

(3) Preparation of free standing electrode of Comparative Example 2

(LCO), carbon black (Super P) and carbon nanotube (MWNT) as a conductive agent, and PVDF as a binder in a ratio of 77: 11.5: 11.5 (wt%) And the free standing electrode according to Comparative Example 2 was dried in a convection oven at 110 DEG C for 30 minutes.

The composition of the metal-based electrode, the free standing electrode according to the embodiment of the present invention and the free standing electrode according to the comparative example are shown in Table 1 below.

electrode
type Electrode name Binder Type Composition (wt%) The electrode active material (LCO) bookbinder Carbon black (Super P) Carbon nanotubes (MWNT) metal
Base electrode Al-PU PU 90 5 5 0 Al-PVDF PVDF 90 5 5 0 free
Standing electrode FS-PU11.5-CNT00 PU 77.0 11.5 11.5 0 Comparative Example 1 FS-PU11.5-CNT50 PU 77.0 11.5 5.75 5.75 Example 1 FS-PU17.9-CNT50 PU 71.4 17.9 5.35 5.35 Example 2 FS-PU20.7-CNT50 PU 69.0 20.7 5.15 5.15 Example 3 FS-PU24.6-CNT50 PU 65.6 24.6 4.90 4.90 Example 4 FS-PVDF11.5-CNT50 PVDF 77.0 11.5 5.75 5.75 Comparative Example 2

(3) Mechanical analysis and micro-organization of free standing electrodes

The stretchability of the electrode was evaluated by measuring the tensile strength of the free standing electrode according to the example of the present invention and the comparative example using a test equipment (instron 5960). The specimens were prepared in the form of 20 mm (L) x 10 mm (W) x 50 μm (T) and pulled at a constant deformation rate of 1 mm / min until cracking occurred in the specimen.

4A and 4B are views showing a manufacturing process of a free standing electrode according to Comparative Example 2 and an embodiment of the present invention.

FIG. 4A is a view showing the production of a free standing electrode according to Comparative Example 2. The slurry (FS-PVDF11.5-CNT50) containing 11.5 wt% of PVDF as a binder was cast on a glass substrate (left side) State (right side). As shown in the right image of FIG. 4A, it can be seen that cracks are generated in the cast film during drying of the solvent (NMP). In Comparative Example 2, it was not possible to perform further analysis on this electrode due to poor mechanical properties.

4B is a perspective view of a free standing electrode according to Example 1 of the present invention. A slurry (FS-PU11.5-CNT50) containing 11.5 wt% of polyurethane as a binder is cast on a glass substrate (left side) , Dried (center), peeled off (right) from the glass substrate. As shown in the figure, Example 1 of the present invention formed a smooth, crack-free state and was very easily separated from the glass substrate. The free standing electrode of the present invention showed very good stability in folding or folding, as seen in the images placed below in Figure 4b.

Although not described here as a comparative example, we have found in previous studies that when using PVDF as a binder, a free standing electrode is obtained only when the amount of PVDF binder is greater than 20 wt%. This indicates that the polyurethane can form a flexible free standing electrode in a lesser amount than PVDF, which means that flexible electrodes can be produced with high energy density.

5A to 5F are SEM images of free standing electrodes according to Example 1 (FS-PU11.5-CNT50) and Comparative Example 1 (FS-PU11.5-CNT00) of the present invention. FIGS. 5A to 5C show a free standing electrode according to Embodiment 1 of the present invention, FIGS. 5A and 5B are views showing the surface of a free standing electrode according to Embodiment 1, Fig. FIGS. 5D to 5F relate to a free standing electrode according to Comparative Example 1, FIGS. 5D and 5E are views showing a surface of a free standing electrode according to Comparative Example 1, FIG. 5F shows a free standing electrode according to Comparative Example 1, Fig.

(LCO) and carbon black (super P) particles are uniformly distributed throughout the electrode along the network provided by carbon nanotube (MWNT) and polyurethane (PU) binders, as shown in Figs. 5A and 5B. This uniform distribution can be seen also in Fig. 5C.

5d to 5f, the free standing electrode (FS-PU11.5-CNT00) of Comparative Example 1, which does not include carbon nanotubes (MWNT), has a uniformly dispersed electrode active material (LCO) Many voids are observed between the carbon black (Super P) particles. These voids are expected to interfere with electron transport in the electrode or adversely affect the mechanical properties of the electrode.

The effect of addition of carbon nanotubes (MWNT) was also examined by comparing the tensile strength and electron conductivity of the free standing electrode according to Example 1 and Comparative Example 1. 6A shows the stress-strain curve of the free standing electrode. In this figure, the addition of carbon nanotubes (MWNT) shows improved mechanical properties. Comparative Example 1 (FS-PU11.5-CNT00) exhibited an elongation of only 13.1% at a tensile stress of 3.73 MPa. In contrast, Example 1 (FS-PU11.5-CNT50) according to the present invention exhibited an elongation of 24.9% under the same load and fractured at 4.63 MPa. That is, when the carbon nanotube (MWNT) is added to the free standing electrode as in Example 1, the tensile strain of the electrode is doubled at the maximum load.

As described above, the free standing electrode of Comparative Example 1 (FS-PU11.5-CNT00) contains many voids in the electrode that prevent close contact between the binder and the active material and reduce the bonding region (Fig. 5e) Thereby weakening the mechanical properties of the electrode. On the other hand, in the free standing electrode according to the first embodiment of the present invention including the carbon nanotube (MWNT), the pores are much smaller and the polyurethane and the carbon nanotube (MWNT) are in contact with each other over a wide area in a dense structure ) To improve the mechanical strength.

At the same time, the presence of the carbon nanotube (MWNT) increases the electron conductivity of the free standing electrode as shown in FIG. 6B. The free standing electrode of Example 1 (FS-PU11.5-CNT50) of the present invention had an electronic conductivity of 2.73 S / cm corresponding to about 4.5 times of the free standing electrode of Comparative Example 1 (FS-PU11.5-CNT00) .

The excellent stretching property of the free standing electrode of Example 1 of the present invention shows excellent impact resistance against impact, which means that the free standing electrode of Example 1 exhibits excellent toughness.

As described above, the polyurethane binder and the free standing electrode including the carbon nanotube have excellent mechanical properties, thereby lowering the risk of damage due to external force and having a high electric conductivity, and thus are very suitable for use in a flexible electrode can do.

(3) Electrochemical analysis of free standing electrodes

First, the compatibility of the polyurethane used as the binder in the present invention with the organic solvent was tested, and the results are shown in Table 2.

PC EC / DEC EC / EMC AN DOL / DME Is polyurethane soluble? Insoluble Dissolution Dissolution Dissolution Dissolution

A solution of 1.0 M LiBF ₄ was used as the electrolyte and glass fiber was used as the separator. Lithium metal was used as a counter electrode and a coin-type half cell was fabricated in a glove box filled with argon. Electrochemical characteristics were tested while charging and discharging cells in the CC / CV and CC modes, respectively, in the potential range of 3.0 V to 4.3 V (vs. Li ⁺ / Li). The speed characteristics of the electrodes were measured at various current densities of 0.1 C to 5 C and the cycling stability was measured at a charge density of 0.5 C charge / 1 C discharge.

7A and 7B are graphs showing electrochemical characteristics of the free standing electrode of Example 1 and Comparative Example 1 of the present invention. 7A and 7B show the velocity characteristics of the electrode measured while adjusting the current density to 0.1 to 5 DEG C. FIG. At low current density, the initial capacity was almost similar regardless of the presence of carbon nanotubes (MWNTs). However, the free standing electrode of Example 1 (FS-PU11.5-CNT50) exhibited a large overvoltage at the beginning of charging. At the same time, the free standing electrode of Example 1 (FS-PU11.5-CNT50) provides a higher capacity over a wide range of discharge current density.

The free standing electrode of Example 1 (FS-PU11.5-CNT50) of the present invention maintained a high discharge capacity of 101.08 mAh / g while the free standing electrode of Comparative Example 1 (FS-PU11.5-CNT00) 2 > C. ≪ / RTI > From these results, it can be seen that carbon nanotubes (MWNTs) give better speed capability of the free standing electrode.

7C is a graph showing the cycling stability of the free standing electrode according to Example 1 and Comparative Example 1 of the present invention. In order to investigate the cycling stability, the free standing electrodes were subjected to a cycle life test at a constant current density of 0.5 C charge / 1 C discharge at room temperature, and the results are shown in FIG. 7C.

From FIG. 7C, it can be seen that the cycle stability of the free standing electrode is significantly improved by putting the carbon nanotube (MWNT) into the electrode. The free standing electrode according to Example 1 (FS-PU11.5-CNT50) of the present invention maintained 94.29% of the initial capacity even after 100 cycles, while the free standing electrode according to Comparative Example 1 (FS-PU11.5-CNT00) The retention rate of the electrode was only 85.40%.

Hereinafter, the influence of the amount of the polyurethane binder on the electrochemical performance of the free standing electrode will be examined.

The compositions of the examples of the present invention are shown in Table 1, wherein the amount of the conductive agent was maintained at a substantially constant level in order to maximize the effect of the conductive agent.

Figure 8a shows the initial discharge capacities of the free standing electrodes of Examples 1 to 4 of the present invention comprising various amounts of polyurethane binder from 11.5 wt% to 24.6 wt%. As the amount of polyurethane decreased from 24.6 wt% to 17.9%, the discharge capacity of the free standing electrode increased from 142.26 mAh / g to 151.30 mAh / g. From 17.9 wt%, the decrease in the amount of polyurethane did not affect the discharge capacity. Example 1 (FS-PU11.5-CNT50) and Example 2 (FS-PU17.9-CNT50) exhibited approximately the same capacity of about 151 mAh / g.

8B is a graph showing discharge capacities at various current densities of the free standing electrodes according to Examples 1 to 4 of the present invention. As with capacities at low current densities, electrodes with low polyurethane content exhibited significantly higher discharge capacities at all current densities.

(FS-PU11.5-CNT50) and Example 2 (FS-PU17.9-CNT50) at a low current density of 0.1C, Discharge electrode. However, as the current density increased, the discharge capacity was similar to that of Example 4 (FS-PU24.6-CNT50). The relatively low discharge capacity of a freestanding electrode with a relatively large amount of polyurethane may be due to the inherent high resistance of the polyurethane.

8C is a graph showing the cycle stability of the free standing electrode according to Examples 1 to 4 of the present invention. Similar to the speed characteristics, the capacity maintenance ratio of the free standing electrode of the present invention increased from 84.54% to 97.49% after 100 cycles, while the amount of polyurethane decreased from 24.6 wt% to 17.9 wt%.

Finally, a full cell was fabricated using a free standing electrode according to Example 1 (FS-PU11.5-CNT50) of the present invention, and LEDs were illuminated using all the cells (Figs. 9A and 9B). The anode was made identical to the cathode using graphite as the anode material. That is, polyurethane was used as a binder and carbon nanotubes (MWNT) were added. As shown in Figs. 9A and 9B, the LED is lit in a full cell even in a bent state without any problem.

From the above results it can be advantageously applied to flexible free standing electrodes because the free standing electrode can be made using a much smaller amount of polyurethane binder than PVDF and the polyurethane imparts good mechanical properties to the electrode. Further, the free standing electrode according to the present invention can overcome the problem of poor electrical conductivity of the polyurethane with the help of the added carbon nanotube (MWNT).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

Claims (13)

As a flexible secondary battery electrode
A flexible secondary battery electrode made from a slurry comprising an electrode active material, a polyurethane as a binder, and a conductive agent containing carbon. The method according to claim 1,
Wherein the polyurethane contains 5 to 25 wt% of the polyurethane.
The method of claim 2,
Wherein the polyurethane contains 11.5 wt% of the polyurethane.
The method according to claim 1,
Wherein the conductive agent is contained in an amount of 2 to 30 wt%.
The method of claim 4,
Wherein the conductive agent comprises carbon black and carbon nanotubes.
The method of claim 5,
Wherein the conductive agent contains 50% of carbon black and carbon nanotubes.
The method according to claim 1,
Wherein the electrode active material comprises lithium, cobalt, and oxygen.
A flexible secondary battery electrode manufacturing method comprising:
(I) preparing a slurry comprising an electrode active material, a polyurethane as a binder, and a conductive agent comprising carbon;
(Ii) casting the slurry onto a substrate; And
(Iii) removing the cast slurry from the substrate.
The method of claim 8,
And drying the cast slurry prior to the desorption of step (iii).
The method of claim 8,
Wherein the polyurethane contains 5 to 25 wt% of the polyurethane.
The method of claim 10,
Wherein the polyurethane contains 11.5 wt% of the polyurethane.
The method of claim 8,
Wherein the conductive agent comprises carbon black and CNT.
The flexible secondary battery according to any one of claims 1 to 6, wherein the metal current collector is excluded.

Images