TECHNICAL FIELD
The present application claims priority to Korean Patent Application No. 10-2020-
0117954 filed on September 14, 2020 in the Republic of Korea. The present disclosure
relates to a current collector for a negative electrode of a solid-state battery which shows
10 high lithium metal electrodeposition efficiency, and a negative electrode for a solid-state
battery including the same.
BACKGROUND ART
There is an imminent need for developing a solid-state battery using a solid
15 electrolyte in order to solve the safety problem of a secondary battery using a liquid
electrolyte.
Since lithium is the lightest metal and has a low reduction potential (-3.04 V vs.
SHE) and high theoretical capacity (3860 mAh/g), it has been studied as a next-generation
negative electrode material. In the case of a lithium secondary battery using lithium
20 metal as an electrode, an electrode having a small thickness is required to maximize the
efficiency and energy density of the battery. However, there is a limitation in forming
lithium foil having a predetermine level of thickness or less merely through a conventional
physical pressing process for forming lithium foil. Meanwhile, a negative electrode has
PCT/KR2021/012534
2021-09-14
2
been manufactured by using a current collector alone without negative electrode active
material (layer) in manufacturing a solid-state battery. In addition, the battery is operated
by forming a lithium metal plating film through the lithium electrodeposition on the
surface of the negative electrode current collector, while lithium ions are reduced during
5 charge.
In general, a conductive metal, such as copper, is used as a negative electrode
current collector, and there has been an attempt to carry out a method for increasing
lithium electrodeposition efficiency by modifying (coating etc.) the metal surface. Such a
method includes coating with a lithiophilic metal, such as Ag, or coating with a
10 carbonaceous material, such as carbon black. In addition, a mixture containing silver and
carbon has been attempted as a coating layer material. However, this cannot provide high
performance in terms of resistance or charge/discharge efficiency. Therefore, there is a
need for developing a negative electrode current collector or an active material-free
negative electrode for a solid-state battery having improved electrochemical properties.
15
DISCLOSURE
Technical Problem
The present disclosure is designed to solve the problems of the related art, and
therefore the present disclosure is directed to providing a current collector for a negative
20 electrode which shows high lithium electrodeposition efficiency by coating the surface of a
negative electrode current collector with metal-carbon composite particles, and a negative
electrode for a solid-state battery including the current collector for a negative electrode.
The present disclosure is also directed to providing a method for preparing the metalPCT/
KR2021/012534
2021-09-14
3
carbon composite particles. It will be easily understood that the objects and advantages
of the present disclosure may be realized by the means shown in the appended claims and
combinations thereof.
5 Technical Solution
According to an embodiment of the present disclosure, there is provided a negative
electrode current collector for a solid-state battery, which includes an electroconductive
metal foil, and a coating layer formed on the surface of the metal foil and including metalcarbon
composite particles, wherein the metal-carbon composite particles include metal
10 particles and carbon particles with at least one metal particle attached to at least one carbon
particle, the composite particles have a particle diameter of 20 μm or less, and the content
of metal in the composite particles is 50 parts by weight or less, based on 100 parts by
weight of carbon.
According to the second embodiment of the present disclosure, there is provided
15 the negative electrode current collector for a solid-state battery as defined in the first
embodiment, wherein the metal particle includes at least one selected from the group
consisting of Ni, Cu, Ag, Au, Pt, Al, Zn and Bi.
According to the third embodiment of the present disclosure, there is provided the
negative electrode current collector for a solid-state battery as defined in the first or the
20 second embodiment, wherein the carbon particle includes at least one selected from natural
graphite, artificial graphite, hard carbon, soft carbon, carbon black, acetylene black, ketjen
black, channel black, furnace black, lamp black, thermal black, carbon nanotubes, fullerene,
carbon fibers and fluorocarbon.
PCT/KR2021/012534
2021-09-14
4
According to the fourth embodiment of the present disclosure, there is provided a
negative electrode for a solid-state battery, which includes the negative electrode current
collector as defined in any one of the first to the third embodiments and does not include
negative electrode active material, wherein lithium is electrodeposited to and detached
from the surface of the 5 metal foil during the operation of a battery.
According to the fifth embodiment of the present disclosure, there is provided the
negative electrode for a solid-state battery as defined in the fourth embodiment, wherein
lithium is electrodeposited between the metal foil and the coating layer.
According to the sixth embodiment of the present disclosure, there is provided the
10 negative electrode current collector or negative electrode for a solid-state battery as defined
in any one of the first to the fifth embodiments, wherein the metal particle and the carbon
particle are attached to each other chemically, physically or both.
According to the seventh embodiment of the present disclosure, there is provided a
solid-state battery, which includes the negative electrode as defined in the fourth or the
15 fifth embodiment.
According to the eighth embodiment of the present disclosure, there is provided a
method for preparing composite particles, including the steps of: preparing a reaction
solution containing a metal salt and a carbonaceous material, and carrying out reaction in
such a manner that metal particles may be grown on the surface of the carbonaceous
20 material in the reaction solution.
According to the ninth embodiment of the present disclosure, there is provided the
method for preparing composite particles as defined in the eighth embodiment, wherein the
reaction solution has a solid content including the metal salt and the carbonaceous material,
PCT/KR2021/012534
2021-09-14
5
except a solvent, of 30 wt% or less.
According to the tenth embodiment of the present disclosure, there is provided the
method for preparing composite particles as defined in the eighth or the ninth embodiment,
wherein the metal salt is at least one of metal chloride, metal iodide, metal cyanide, metal
bromide, metal sulfide, 5 metal hydroxide, metal phosphite and metal chloride hydrate.
According to the eleventh embodiment of the present disclosure, there is provided
the method for preparing composite particles as defined in any one of the eighth to the
tenth embodiments, wherein the metal salt is chloride of at least one metal selected from Ni,
Cu, Ag, Au, Pt, Al, Zn and Bi.
10
Advantageous Effects
The metal-carbon composite particles according to the present disclosure allows
homogeneous introduction of metal particles to the surface of a current collector.
Therefore, it is possible to induce homogeneous lithium electrodeposition between a
15 coating layer including the metal-carbon composite particles and a conductive metal, and
to form a uniform lithium metal plating film on the surface of a negative electrode current
collector.
In addition, the method for preparing metal-carbon composite particles allows
formation of a composite of metal particles with a carbonaceous material having a fine size.
20 As a result, when the resultant composite particles are introduced to a solid-state battery,
lithium may be electrodeposited homogeneously on the surface of a current collector, as
mentioned above.
PCT/KR2021/012534
2021-09-14
6
DESCRIPTION OF DRAWINGS
The accompanying drawings illustrate a preferred embodiment of the present
disclosure and together with the foregoing disclosure, serve to provide further
understanding of the technical features of the present disclosure, and thus, the present
disclosure is not construed as being limited to the 5 drawing. Meanwhile, shapes, sizes,
scales or proportions of some constitutional elements in the drawings may be exaggerated
for the purpose of clearer description.
FIG. 1 is a schematic view illustrating how lithium is electrodeposited to a
negative electrode current collector to form a plating film according to an embodiment of
10 the present disclosure.
FIG. 2 to FIG. 4 illustrate the composite particles obtained according to Examples
1 to 3, respectively.
BEST MODE
15 Hereinafter, preferred embodiments of the present disclosure will be described in
detail with reference to the accompanying drawings. Prior to the description, it should be
understood that the terms used in the specification and the appended claims should not be
construed as limited to general and dictionary meanings, but interpreted based on the
meanings and concepts corresponding to technical aspects of the present disclosure on the
20 basis of the principle that the inventor is allowed to define terms appropriately for the best
explanation. Therefore, the description proposed herein is just a preferable example for
the purpose of illustrations only, not intended to limit the scope of the disclosure, so it
should be understood that other equivalents and modifications could be made thereto
PCT/KR2021/012534
2021-09-14
7
without departing from the scope of the disclosure.
Throughout the specification, the expression ‘a part includes an element’ does not
preclude the presence of any additional elements but means that the part may further
include the other elements.
As used herein, the terms ‘about’, ‘substantia 5 lly’, or the like, are used as meaning
contiguous from or to the stated numerical value, when an acceptable preparation and
material error unique to the stated meaning is suggested, and are used for the purpose of
preventing an unconscientious invader from unduly using the stated disclosure including
an accurate or absolute numerical value provided to help understanding of the present
10 disclosure.
As used herein, the expression ‘A and/or B’ means ‘A, B or both of them’.
The present disclosure relates to a negative electrode current collector, and a
negative electrode for an electrochemical device including the negative electrode current
collector. The electrochemical device may be a solid-state battery using a solid
15 electrolyte as an electrolyte material. In addition, the solid-state battery may be a lithiumion
secondary battery.
According to the present disclosure, the negative electrode current collector
includes a metal foil, and a coating layer formed on at least one surface of the metal foil
and including metal-carbon composite particles.
20 According to the present disclosure, the negative electrode current collector may
be applied to a battery with no electrode active material coated thereon. In other words,
the negative electrode current collector functions as an active material-free negative
electrode in a solid-state battery, and lithium is electrodeposited on the surface of the metal
PCT/KR2021/012534
2021-09-14
8
foil during the charge of the battery so that electrochemical reactions may be carried out.
FIG. 1 is a schematic view illustrating the negative electrode current collector and the
process of lithium electrodeposition on the surface of the metal foil according to an
embodiment of the present disclosure. Referring to FIG. 1, the negative electrode current
collector includes a metal foil and a coating layer 5 formed on the surface of the metal foil.
In FIG. 1, reference numeral 21 represents aggregation of composite particles. As shown
in FIG. 1, the coating layer may be a porous layer having pores, and lithium ions pass
through the coating layer during charge, arrive at the surface of the metal foil and are
electrodeposited to form a lithium metal layer 22. Herein, the term ‘electrodeposition’
10 may refer to deposition.
The metal foil may have a thickness of 3-500 μm. The metal foil is not
particularly limited, as long as it has conductivity, while not causing any chemical change
in the battery to which the current collector according to the present disclosure is applied.
Particular examples of the negative electrode current collector include copper, stainless
15 steel, aluminum, nickel, titanium, aluminum-cadmium alloy, or the like. According to an
embodiment of the present disclosure, fine surface irregularities may be formed on the
surface of the metal foil to increase the binding force with the coating layer or the plated
lithium metal plating film electrodeposited to the metal foil. Meanwhile, according to an
embodiment of the present disclosure, the metal foil may have various shapes, such as a
20 film, a sheet, a foil, a net, a porous body, a foam or a non-woven web body.
According to the present disclosure, the coating layer may have a thickness of 5-50
μm, but is not limited thereto. According to an embodiment of the present disclosure, the
metal-carbon composite particles may be present in an amount of 90 wt% or more, based
PCT/KR2021/012534
2021-09-14
9
on 100 wt% of the coating layer. For example, the composite particles may be present in
an amount of 95 wt% or more, or 97 wt% or more, based on 100 wt% of the coating layer.
According to an embodiment of the present disclosure, in the metal-carbon
composite particles, carbon particles and metal particles are attached to each other, or one
type of particles are coated with the other type 5 of particles. According to the present
disclosure, the term ‘attached/coated’ may refer to carbon particles and metal particles
bound physically and/or chemically to each other.
FIG. 2 to FIG. 4 are scanning electron microscopic (SEM) images illustrating the
composite particles obtained according to Examples 1-3, respectively. Referring to FIG.
10 2 to FIG. 4, the metal-carbon composite particles include carbon particles and metal
particles attached to each other.
According to an embodiment of the present disclosure, the metal-carbon
composite particles may have a size (diameter) of 20 μm or less based on the longest
diameter of the particles. Within the above-defined range, the composite particles may
15 have a particle size of 10 μm or less, 5 μm or less, or 1 μm or less. Meanwhile, the
composite particles may include a plurality of carbon particles. Meanwhile, the
composite particles may include a plurality of metal particles. According to an
embodiment of the present disclosure, the particle diameter may be determined by using
the laser diffraction method.
20 According to an embodiment of the present disclosure, the carbon particle may
include natural graphite, artificial graphite, hard carbon, soft carbon, carbon black,
acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black,
carbon nanotubes, fullerene, carbon fibers and fluorocarbon.
PCT/KR2021/012534
2021-09-14
10
According to the present disclosure, the metal particle may be a lithiophilic metal,
and particular examples thereof include any one of Ni, Cu, Ag, Au, Pt, Al, Zn, Bi, or the
like, or a combination of two or more of them. Introduction of such a lithiophilic metal
facilitates formation of a stable and homogeneous lithium layer on the surface of a current
5 collector.
Meanwhile, according to an embodiment of the present disclosure, the content of
metal in the metal-carbon composite particles may be 1-50 parts by weight, based on 100
parts by weight of the carbonaceous material.
FIG. 1 illustrates the negative electrode current collector and the mechanism of
10 forming a lithium metal plating film through the lithium electrodeposition on the negative
electrode current collector according to an embodiment of the present disclosure.
Referring to FIG. 1, a coating layer having a predetermined thickness is formed on the
surface of the metal foil, and the coating layer includes the metal-carbon composite
particles having the above-mentioned constitutional characteristics. According to an
15 embodiment of the present disclosure, the coating layer may have an integral layered
structure formed through the packing of the composite particles, and has a porous structure
having pores derived from the interstitial volumes among the composite particles. The
pores may be provided as lithium-ion channels during the charge/discharge of a battery.
Therefore, the negative electrode current collector is provided to the manufacture of a
20 battery in an electrode active material-free state, and lithium ions supplied from a positive
electrode upon the initial charge in a battery activation step pass through the coating layer
and are electrodeposited on the surface of the metal foil, thereby forming a plating film.
Therefore, the negative electrode subjected to the activation step may include a lithium (Li)
PCT/KR2021/012534
2021-09-14
11
plating film electrodeposited thereon. The lithium plating film electrodeposited on the
negative electrode allows continuous electrodeposition/release of lithium ions during the
subsequent charge/discharge cycles of the lithium secondary battery, and thus contributes
to the reversible capacity of the negative electrode.
According to an embodiment 5 of the present disclosure, the metal-carbon
composite particles may be prepared as follows.
First, a metal salt and a carbonaceous material are introduced to and dispersed in a
solvent to prepare a reaction solution. The solvent may include an organic solvent, such
as N-methyl pyrrolidone (NMP), dimethyl formamide (DMF), acetone or dimethyl
10 acetamide, or C3 or lower alcohol, water, or the like. Such solvents may be used alone or
in combination. However, the solvent is not limited to the above-mentioned examples,
and is not particularly limited, as long as it does not affect the physical and/or chemical
properties of the ingredients, such as the metal salt or the carbonaceous material.
According to an embodiment of the present disclosure, the metal salt may be prepared as a
15 solution (first solution) dissolved in water or alcohol. In addition, the carbonaceous
material may be prepared as a dispersion (second solution) in an organic solvent. The
prepared first solution is mixed with the second solution to prepare a reaction solution.
According to an embodiment of the present disclosure, the reaction solution may have a
solid content, except the solvent, controlled to 30 wt% or less, 20 wt% or less, 10 wt% or
20 less, 5 wt% or less, or 3 wt% or less. Meanwhile, the solid content of the metal in the
reaction solution may be controlled to a suitable range considering the size of the
composite particles or the content of the metal particles in the composite particles.

WHAT IS CLAIMED IS:
1. A negative electrode current collector for a solid-state battery, which
comprises an electroconductive metal foil, and a coating layer formed on the surface of the
metal foil and 5 comprising metal-carbon composite particles,
wherein the metal-carbon composite particles comprise metal particles and carbon
particles with at least one metal particle attached to at least one carbon particle, the
composite particles have a particle diameter of 20 μm or less, and the content of metal in
the composite particles is 50 parts by weight or less based on 100 parts by weight of
10 carbon.
2. The negative electrode current collector for a solid-state battery according
to claim 1, wherein the metal particle comprises at least one selected from the group
consisting of Ni, Cu, Ag, Au, Pt, Al, Zn and Bi.
15
3. The negative electrode current collector for a solid-state battery according
to claim 1, wherein the carbon particle comprises at least one selected from natural
graphite, artificial graphite, hard carbon, soft carbon, carbon black, acetylene black, ketjen
black, channel black, furnace black, lamp black, thermal black, carbon nanotubes, fullerene,
20 carbon fibers and fluorocarbon.
4. A negative electrode for a solid-state battery which comprises the negative
electrode current collector as defined in claim 1 and comprises no negative electrode active
PCT/KR2021/012534
2021-09-14
27
material, wherein lithium is electrodeposited to and detached from the surface of the metal
foil during the operation of a battery.
5. The negative electrode for a solid-state battery according to claim 4,
wherein lithium is electrodeposited be 5 tween the metal foil and the coating layer.
6. The negative electrode for a solid-state battery according to claim 1,
wherein the metal particle and the carbon particle are attached to each other chemically,
physically or both.
10
7. A solid-state battery comprising the negative electrode as defined in claim 5.
8. A method for preparing composite particles, comprising the steps of:
preparing a reaction solution containing a metal salt and a carbonaceous material,
15 and
carrying out reaction in such a manner that metal particles may be grown on the
surface of the carbonaceous material in the reaction solution.
9. The method for preparing composite particles according to claim 8, wherein
20 the reaction solution has a solid content including the metal salt and the carbonaceous
material, except a solvent, of 30 wt% or less.
10. The method for preparing composite particles according to claim 8, wherein
PCT/KR2021/012534
2021-09-14
28
the metal salt is at least one of metal chloride, metal iodide, metal cyanide, metal bromide,
metal sulfide, metal hydroxide, metal phosphite and metal chloride hydrate.
11. The method for preparing composite particles according to claim 8, wherein
the metal salt is chloride of at least one metal selected 5 from Ni, Cu, Ag, Au, Pt, Al, Zn and
Bi.