TECHNICAL FIELD
Cross-reference to Related Applications
[0001] This application claims priority from Korean Patent
Application No. 10-2021-0036124, filed on March 19, 2021, the
disclosure of which is incorporated by reference herein.
10 Technical Field
[0002] The present invention relates to an electrode and a
secondary battery including the same, wherein the electrode
includes an electrode active material layer, the electrode
active material layer includes an electrode active material;
15 a conductive agent; and sodium dodecyl sulfate (SDS), the
conductive agent includes a carbon nanotube structure in which
2 to 5,000 single-walled carbon nanotube units are bonded to
each other, and a weight ratio of the carbon nanotube structure
to the SDS may be in a range of 1:3 to 1:30.
20 BACKGROUND ART
[0003] A typical example of an electrochemical device using
electrochemical energy may be a secondary battery, and there
is a trend that its usage area is expanding more and more. In
recent years, demand for secondary batteries as an energy
25 source has been significantly increased as technology
3
development and demand with respect to portable devices, such
as portable computers, mobile phones, and cameras, have
increased, and, among these secondary batteries, lithium
secondary batteries having high energy density, i.e., high
5 capacity, have been subjected to considerable research and
have been commercialized and widely used.
[0004] In general, a secondary battery is composed of a
positive electrode, a negative electrode, an electrolyte, and
a separator. The positive electrode and the negative electrode
10 each are generally composed of an electrode collector and an
electrode active material layer formed on the electrode
collector, and the electrode active material layer is prepared
by a method in which the electrode current collector is coated
with an electrode slurry composition including an electrode
15 active material, a conductive agent, and a binder, dried and
then rolled.
[0005] Typically, a point-type conductive agent, such as
carbon black, has mainly been used as the conductive agent for
a secondary battery, but, with respect to the point-type
20 conductive agent, there was a problem in that an effect of
improving electrical conductivity was not sufficient. In
order to improve this problem, studies on the application of
a line-type conductive agent, such as carbon nanotube (CNT) or
carbon nanofiber (CNF), and a plane-type conductive agent,
25 such as graphene, are being actively conducted.
4
[0006] However, the plane-type conductive agent, such as
graphene, has excellent electrical conductivity, but has a
problem in that it is difficult to prepare thin single layer
graphene, and, in a case in which thick graphene is used,
5 battery efficiency may be reduced. Also, with respect to the
plane-type conductive agent, electrolyte solution mobility may
be limited in the battery due to a wide planar contact.
[0007] With respect to the line-type conductive agent such as
carbon nanotube or carbon nanofiber, electrical conductivity
10 is excellent, but, since dispersibility in a slurry is poor
due to the nature of the material itself growing in a bundle
type or an entangled type, there is a problem in that coating
properties and processability are poor and the line-type
conductive agent is not evenly distributed in the electrode
15 active material layer. In order to improve this problem, there
have been attempts to improve the dispersibility by introducing
a functional group into the line-type conductive agent, but,
in this case, since a surface side reaction occurs due to the
presence of the functional group, there is a problem in that
20 electrochemical properties are deteriorated.
[0008] Also, in order to use carbon nanotubes, it is common
to use a conductive agent dispersion in which bundle type
carbon nanotubes are dispersed by using a dispersant. However,
since many surface defects of the carbon nanotubes occur due
25 to external force in the dispersion process, mechanical
5
strength and electrical conductivity of the carbon nanotubes
are reduced, and thus, there is a problem in that electrode
resistance is increased and lifetime of the battery is reduced.
Furthermore, since sizes of the dispersed carbon nanotubes are
5 not uniform, there is also a problem in that electrode adhesion
and electrode lifetime are reduced.
[0009] Therefore, there is a need to develop an electrode
which includes carbon nanotubes having a minimum of surface
defects and having a relatively constant size.