【TECHNICAL FIELD】
Cross Citation with Related Application(s)
This application claims the benefit of Korean Patent Application No. 10-2021-0004143
10 filed on January 12, 2021 and Korean Patent Application No. 10-2022-0002294 filed on January
6, 2022 in the Korean Intellectual Property Office, the contents of which are incorporated herein
by reference in their entirety.
The present disclosure relates to a freestanding film, an electrode for secondary battery, a
secondary battery including the same, and a method of manufacturing the electrode, and more
15 particularly to a freestanding film having improved peel strength and adhesive force, an electrode
for secondary battery, a secondary battery including the same, and a method of manufacturing the
electrode.
【BACKGROUND】
Along with the technology development and increased demand for mobile devices, demand
20 for secondary batteries as energy sources has been increasing rapidly. Among these secondary
batteries, a lithium secondary battery having high energy density and a high voltage, a long cycle
lifespan, and a low self-discharge rate is commercially available and widely used.
In particular, a secondary battery has attracted considerable attention as an energy source
for power-driven devices, such as an electric bicycle, an electric vehicle, and a hybrid electric
25 vehicle, as well as an energy source for mobile devices, such as a mobile phone, a digital camera,
a laptop computer and a wearable device.
In addition, as interest in environmental issues grows, studies are frequently conducted on
an electric vehicle, a hybrid electric vehicle, etc. which can replace a vehicle using fossil fuels
3
such as a gasoline vehicle and a diesel vehicle, which are one of the main causes of air pollution.
Although a nickel metal hydride secondary battery is mainly used as a power source for the electric
vehicle and the hybrid electric vehicle, research on the use of a lithium secondary battery having
high energy density and discharge voltage is actively being conducted, a part of which are in the
5 commercialization stage.
Conventional electrodes for secondary batteries have generally been manufactured in a wet
manner. However, when the electrode is manufactured in a wet manner, a heat treatment process
at a high temperature is essentially required, and there is a risk that the metal oxide may be
damaged. Therefore, there is a growing need to develop an electrode manufactured in a dry
10 manner.
【DETAILED DESCRIPTION OF THE INVENTION】
【Technical Problem】
It is an object of the present disclosure to provide a freestanding film having improved peel
15 strength and adhesive force, an electrode for secondary battery, a secondary battery including the
same, and a method of manufacturing the electrode.
The objects of the present disclosure are not limited to the aforementioned objects, and other
objects which are not described herein should be clearly understood by those skilled in the art from
the following detailed description and the accompanying drawings.
20 【Technical Solution】
According to one aspect of the present disclosure, there is provided a freestanding film
comprising a pattern having directionality on at least one surface.
The pattern may be a concave-convex pattern.
The pattern may have an interval of 100 ㎛ to 2000 ㎛.
25 The pattern may have a depth of 1.5 ㎛ to 35 ㎛.
According to another aspect of the present disclosure, there is provided an electrode for
secondary battery comprising: an electrode current collector; and an electrode layer located on
the electrode current collector, wherein the electrode layer may include an electrode composition
4
in which an active material, a conductive material, and a binder are dry-mixed, wherein the
electrode composition may be prepared into a freestanding film, and wherein the freestanding film
may include a pattern having directionality on at least one surface.
The pattern may be a concave-convex pattern.
5 The pattern may have an interval of 100 ㎛ to 2000 ㎛.
The pattern may have a depth of 1.5 ㎛ to 35 ㎛.
The freestanding film may be attached to the electrode current collector so that one surface
on which the pattern is formed is in contact with the electrode current collector.
The active material may include at least one selected from the group consisting of lithium
10 cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide, lithium copper
oxide (Li2CuO2), vanadium oxide, a Ni-site type lithium nickel oxide, lithium manganese
composite oxide, lithium manganese composite oxide having a spinel structure, LiMn2O4 in which
a part of Li in formula is substituted with an alkaline earth metal ion, a disulfide compound,
Fe2(MoO4)3, and lithium manganese oxide (LMO).
15 The binder may include polytetrafluoroethylene (PTFE).
The freestanding film may have a peel strength of 10 gf/20 mm or more and 15 gf/20 mm or
less.
According to yet another aspect of the present disclosure, there is provided a method of
manufacturing an electrode for secondary battery, the method comprising the steps of: dry-mixing
20 an active material, a conductive material, and a binder to prepare a mixture; applying a shear force
to the mixture to produce a freestanding film; forming a pattern having directionality at regular
intervals on the freestanding film; and attaching the freestanding film onto an electrode current
collector to form an electrode for a secondary battery.
The pattern may be a concave-convex pattern.
25 The pattern may have an interval of 100 ㎛ to 2000 ㎛.
The pattern may have a depth of 1.5 ㎛ to 35 ㎛.
The freestanding film may be attached to the electrode current collector so that one surface
on which the pattern is formed is in contact with the electrode current collector.
5
The step of forming the pattern may include any of a step of forming the pattern on the
freestanding film by an embossing pattern formed on a roll for winding the freestanding film, a
step of adjusting the speed of the roll, and a step of setting a gear ratio of the 2 roll mill differently.
The step of setting the gear ratio of the two roll mill differently may include a step of setting
5 the gear ratio differently to generate a backlash.
The binder may include polytetrafluoroethylene (PTFE).
According to yet another aspect of the present disclosure, there is provided a secondary battery
comprising the above-mentioned freestanding film.
【Advantageous Effects】
10 According to embodiments of the present disclosure, an electrode for a secondary battery can
be manufactured by a dry method comprising the step of forming a pattern on a freestanding film,
thereby improving the peel strength and adhesive force.
The effects of the present disclosure are not limited to the effects mentioned above and
additional other effects not described above will be clearly understood from the description of the
15 appended claims by those skilled in the art.