Secondary battery
Provided is a secondary battery which includes: one or more positive electrodes including a positive electrode active material layer; a plurality of negative electrodes including a first negative electrode including a silicon-based active material and a second negative electrode including a carbon-based active material; a separator; and an electrolyte, wherein the positive electrode and the negative electrode are alternately stacked with the separators interposed therebetween, and the ratio of weight of the silicon-based active material included in the first negative electrode and weight of the carbon-based active material included in the second negative electrode is in the range of 40:60 to 90:10.
1 . A secondary battery comprising:
one or more positive electrodes including a positive electrode active material layer;
a plurality of negative electrodes including:
a first negative electrode including a silicon-based active material, and
a second negative electrode including a carbon-based active material,
wherein the first negative electrode does not include the carbon-based active material,
wherein the second negative electrode does not include the silicon-based active material;
separators; and
an electrolyte,
wherein one or more positive electrodes and the first or second negative electrode are alternately stacked with the separators interposed therebetween, and
a weight ratio of a total weight of the silicon-based active material of the first negative electrode to a total weight of the carbon-based active material of the second negative electrode in the plurality of negative electrodes is in a range of 49.2:50.8 to 90:10.
2 . The secondary battery of claim 1 , wherein the first negative electrode includes
a first negative electrode current collector, and
a first negative electrode active material layer disposed on one or more surfaces of the first negative electrode current collector, and the first negative electrode active material layer includes the silicon-based active material.
3 . The secondary battery of claim 2 , wherein the first negative electrode active material layer further includes:
a first negative electrode binder, and
a first negative electrode conductive material, and
the first negative electrode active material layer includes:
60 wt % to 90 wt % of the silicon-based active material,
5 wt % to 30 wt % of the first negative electrode binder, and
5 wt % to 20 wt % of the first negative electrode conductive material.
4 . The secondary battery of claim 3 , wherein the first negative electrode binder includes at least one selected from the group consisting of styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, polyvinyl alcohol, polyacrylic acid, polyethylene glycol, polyacrylonitrile, and polyacrylamide.
5 . The secondary battery of claim 2 , wherein a N 1 /P ratio calculated by Mathematical Equation a is in a range of 2.2 to 3.0:
N
1
/
P
ratio
=
{
(
Discharge
capacity
per
unit
area
of
one
first
negative
electrode
active
material
layer
in
the
first
negative
electrode
)
/
(
Discharge
capacity
per
unit
area
of
one
positive
electrode
active
material
layer
in
the
positive
electrode
)
}
.
[
Mathematical
Equation
a
]
6 . The secondary battery of claim 1 , wherein the silicon-based active material includes a compound represented by Chemical Formula 1:
SiO x , [Chemical Formula 1]
wherein, in Chemical Formula 1, 0≤x<2.
7 . The secondary battery of claim 1 , wherein the silicon-based active material includes Si.
8 . The secondary battery of claim 1 , wherein an average particle diameter (D 50 ) of the silicon-based active material is in a range of 1 μm to 10 μm.
9 . The secondary battery of claim 1 , wherein the second negative electrode includes
a second negative electrode current collector and
a second negative electrode active material layer disposed on one or more surfaces of the second negative electrode current collector, and the second negative electrode active material layer includes the carbon-based active material.
10 . The secondary battery of claim 9 , wherein
the second negative electrode active material layer further includes:
a second negative electrode binder, and
a second negative electrode conductive material, and
the second negative electrode active material layer includes:
90 wt % to 99 wt % of the carbon-based active material,
0.5 wt % to 10 wt % of the second negative electrode binder, and
0.5 wt % to 5 wt % of the second negative electrode conductive material.
11 . The secondary battery of claim 10 , wherein the second negative electrode binder includes at least one selected from the group consisting of a polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, poly(methyl methacrylate), polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer rubber, styrene-butadiene rubber, and fluororubber.
12 . The secondary battery of claim 1 , wherein the carbon-based active material includes at least one selected from the group consisting of artificial graphite, natural graphite, hard carbon, soft carbon, carbon black, graphene, and fibrous carbon.
13 . The secondary battery of claim 1 , wherein an average particle diameter (D 50 ) of the carbon-based active material is in a range of 10 μm to 30 μm.
14 . The secondary battery of claim 9 , wherein a N 2 /P ratio calculated by Mathematical Equation b is in a range of 1.0 to 1.3:
N
2
/
P
ratio
=
{
(
Discharge
capacity
per
unit
area
of
one
second
negative
electrode
active
material
layer
in
the
second
negative
electrode
)
/
(
Discharge
capacity
per
unit
area
of
one
positive
electrode
active
material
layer
in
the
positive
electrode
)
}
[
Mathematical
Equation
b
]
15 . The secondary battery of claim 1 , wherein a N all /P all ratio calculated by Mathematical Equation c is in a range of 2 to 3:
N
all
/
P
all
ratio
=
{
(
Sum
of
discharge
capacity
per
unit
area
of
the
negative
electrodes
present
in
the
secondary
battery
)
/
(
Sum
of
discharge
capacity
per
unit
area
of
the
positive
electrode
present
in
the
secondary
battery
)
}
[
Mathematical
Equation
c
]