DESCRIPTION
ANODE ACTIVE MATERIAL HAVING HIGH DENSITY AND PREPARATION
METHOD THEREOF
TECHNICAL FIELD
The present invention relates to an anode active
material including high-density lithium metal oxide particles,
a lithium secondary battery including the same, and a method
of preparing the anode active material.
BACKGROUND ART
The prices of energy sources have increased due to the
depletion of fossil fuels, the interest in environmental
pollution has been amplified, and the demand for eco-friendly
alternative energy sources has become an indispensable factor
for the future life. Thus, research into various power
generation technigues, such as nuclear power, solar power,
wind power, and tidal power, has continuously conducted, and
great interests in power storage devices for more effectively
using the energy thus generated have also grown.
In particular, with respect to lithium secondary
batteries, the demand as an energy source has rapidly
increased as the technological development and demand for
mobile devices have increased, the use thereof as power
sources of electric vehicles (EVs) or hybrid electric
vehicles (HEVs) has recently been realized, and the
application area has been extended to include uses, such as
an auxiliary power source through power grids and the like.
A carbon-based compound that allows reversible

intercalation and deintercalation of lithium ions as well as
structural and electrical properties being maintained has
mainly been used as an anode active material for an anode of
a typical lithium secondary battery. However, a significant
amount of research into lithium titanium oxides has recently
been conducted.
Since lithium titanium oxides are a zero-strain
material in which structural changes are extremely low during
charging and discharging, lifetime characteristics are
relatively excellent, a relatively high voltage range is
obtained, and dendrites do not occur. Thus, lithium titanium
oxides are known as a material having excellent safety and
stability.
However, with respect to the lithium titanium oxides,
since electrical conductivities thereof may be lower than
those of carbon materials, such as graphite, and atomization
may be required to improve charge rates, there may be a
limitation that a content of a binder may increase to form an
electrode.
DISCLOSURE OF THE INVENTION
TECHNICAL PROBLEM
The present invention provides an anode active material
including lithium metal oxide particles having specific
internal porosity and average particle diameter. Furthermore,
a secondary battery including the anode active material is
provided.
The present invention also provides a method of
preparing the lithium metal oxide particles.
The object of the present invention is not limited to

the aforesaid, but other objects not described herein will be
clearly understood by those skilled in the art from
descriptions below.
TECHNICAL SOLUTION
According to an aspect of the present invention, there
is provided an anode active material including lithium metal
oxide particles, wherein an internal porosity of the lithium
metal oxide particles is in a range of 3% to 8% and an
average particle diameter (D50) thereof is in a range of 5 urn
to 12 urn.
According to another aspect of the present invention,
there is provided a method of preparing lithium metal oxide
particles having an internal porosity ranging from 3% to 8%
and an average particle diameter (D50) ranging from 5 µm to
12 µm, including preparing a precursor solution by adding a
lithium salt and a metal oxide to a volatile solvent and
stirring; providing the precursor solution into a chamber of
a spray dryer; and spraying the precursor solution in the
chamber and drying.
Also, according to another aspect of the present
invention, there is provided an anode including the anode
active material.
Furthermore, according to another aspect of the present
invention, there is provided a secondary battery including
the anode.
ADVANTAGEOUS EFFECTS
As described above, an anode active material according
to the technical idea of the present invention includes high-

density lithium metal oxide particles, and thus, the adhesion
to an anode may be significantly improved. That is, an
amount of a binder required to obtain the same strength of
adhesion to the electrode may be significantly reduced in
comparison to a typical anode active material having a
typical density.
High-density lithium metal oxide particles may be
formed as the internal porosity of the lithium metal oxide
particles decreases. As a result, the amount of the binder
required to prepare an anode slurry may be reduced, and thus,
it is advantageous for the mass production of secondary
batteries.
Since the realization of the high-density lithium metal
oxide and the resultant good adhesion to the electrode may be
possible, an average particle diameter of the lithium metal
oxide particles may be further decreased. As a result, high
rate characteristics of the secondary battery may be improved.
The high-density anode active material may be formed by
a specific preparation method according to an embodiment of
the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a scanning electron microscope (SEM)
micrograph of Li4Ti5O12 of Comparative Example 3; and
FIG. 2 is a SEM micrograph of high-density Li4Ti5O12 of
Example 1 according to an embodiment of the present invention.
MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of the present invention will be
described in more detail with reference to the accompanying

drawings. However, the following embodiments are merely
presented to exemplify the present invention, and the scope
of the present invention is not limited thereto.
An anode active material according to an embodiment of
the present invention includes lithium metal oxide particles,'
wherein an internal porosity of the lithium metal oxide
particles is in a range of 3% to 8% and an average particle
diameter (D50) thereof is in a range of 5 µm to 12 µm.
According to an embodiment of the present invention,
since high-density lithium metal oxide particles having the
specific internal porosity and the average particle diameter
(D50) are included, the adhesion to an anode may be
significantly improved even by using the same or smaller
amount of a binder that is required during the preparation of
an anode slurry. Also, high rate characteristics of a
secondary battery may be improved by further decreasing the
average particle diameter of the lithium metal oxide
particles.
The lithium metal oxide particle according to an
embodiment of the present invention, as a secondary particle
in which two or more primary particles are agglomerated, may
be a porous particulate.
In the case that the lithium metal oxide particles, as
the primary particles, are used in the anode active material
of the lithium secondary battery, the adhesion to the
electrode may not be problematic, but high rate
characteristics may degrade. In order to address the above
limitation, a diameter of the primary particle may be
decreased to 300 nm or less. However, in this case,
limitations in a process of preparing the anode slurry, for

example, an increase in product costs due to the use of a
large amount of the binder or a decrease in electrical
conductivity, may occur due to the increase in a specific
surface area. Therefore, in order to address the limitations
caused by using the primary particles, the lithium metal
oxide particle according to the embodiment of the present
invention may be in the form of a secondary particle, in
which two or more primary particles are agglomerated.
Typically, since the secondary particle may have a
porous shape, a large amount of the binder is required in
order to maintain electrode adhesion. As a result, the
capacity of the battery may be decreased due to the use of
the large amount of the binder.
However, since the lithium metal oxide particles
according to the embodiment of the present invention are
high-density secondary particles having an internal porosity
ranging from 3% to 8%, sufficient electrode adhesion may not
only be obtained but excellent high rate characteristics may
also be obtained, even in the case in which a small amount of
the binder is used in comparison to typical secondary
particles, for example, the binder is used in an amount
ranging from 20% to 50% of a typical amount of the binder
used.
In the case that the internal porosity of the lithium
metal oxide particles is less than 3%, practical difficulties
in terms of a preparation process may occur in consideration
of the fact that the secondary particles are formed by the
agglomeration of the primary particles. In the case in which
the internal porosity of the lithium metal oxide particles is
greater than 8%, the amount of the binder required to

maintain appropriate electrode adhesion may increase, and
thus, the conductivity may be reduced and the capacity may be
decreased. Therefore, the effect of the present invention
aimed at using a small amount of the binder may be
insignificant -
According to an embodiment of the present invention,
the internal porosity of the lithium metal oxide particles
may be defined below:
Internal porosity = volume of pores per unit
mass/(specific volume + volume of pores per unit mass)
The measurement of the internal porosity is not
particularly limited. For example, according to an
embodiment of the present invention, the internal porosity
may be measured by using absorption gas, such as nitrogen,
and BELSORP (Brunauer-Emmett-Teller (BET) instrument) by BEL
Japan, Inc.
Similarly, a specific surface area (BET) of the lithium
metal oxide particles may be in a range of 2 m2/g to 8 m2/g.
According to an embodiment of the present invention,
the specific surface area of the lithium metal oxide
particles may be measured by a BET method. For example, the
specific surface area may be measured by a 6-point BET method
according to a nitrogen gas adsorption-flow method using a
porosimetry analyzer (Belsorp-II mini by Bell Japan Inc.).
The average particle diameter (D50) of the lithium metal
oxide particles may be in a range of 5 urn to 12 urn, and an
average particle diameter of the primary particles
constituting the lithium metal oxide particles may be in a
range of 100 nm to 4 00 nm.
In the present invention, the average particle diameter

(D50) of the lithium metal oxide particles may be defined as
a particle diameter at 50% in a cumulative particle diameter
distribution. The average particle diameter (D50) of the
lithium metal oxide particles according to the embodiment of
the present invention, for example, may be measured by using
a laser diffraction method. The laser diffraction method may
generally measure a particle diameter ranging from a
subraicron level to a few mm, and may obtain highly repeatable
and high resolution results.
Typically, since the lithium metal oxide particles have
low conductivity, it is advantageous to have a small average
particle diameter in order to be applied to a cell for fast
charging. However, in this case, a large amount of the
binder is reguired in order to maintain appropriate electrode
adhesion due to the increase in the specific surface area as
described above. That is, in the case that the average
particle diameter of the lithium metal oxide particles is
less than 5 urn, the amount of the binder required to maintain
desired electrode adhesion may increase due to the increase
in the specific surface area of the anode active material,
and as a result, the reduction of the conductivity of the
electrode may occur. In the case in which the average
particle diameter of the lithium metal oxide particles is
greater than 12 µm, fast charging characteristics may degrade.
Therefore, with respect to lithium metal oxide particles
having an average particle diameter ranging from 5 µm to 12
µm, as the high-density lithium metal oxide particles
according to the embodiment of the present invention, the
amount of the binder required to maintain electrode adhesion
may not only be decreased, but fast charging characteristics

may also be improved by increasing an area, in which a direct
reaction with lithium (Li) ions may be possible.
In the case that the average particle diameter of the
primary particles is less than 100 nm, the electrode adhesion
may decrease due to the increase in the porosity of the
lithium metal oxide particles formed by the agglomeration of
the primary particles. In the case in which the average
particle diameter of the primary particles is greater than
400 nm, the formability of the lithium metal oxide particles
may decrease and granulation may be difficult to be
controlled.
The lithium metal oxide according to an embodiment of
the present invention is a material that may store and
release lithium ions, in which the lithium metal oxide may be
expressed by a compositional formula of LixMyOz (where M is at
least one element independently selected from the group
consisting of titanium (Ti), tin (Sn), copper (Cu), lead (Pb),
antimony (Sb), zinc (Zn), iron (Fe), indium (In), aluminum
(Al) , or zirconium (Zr) , and x, y, and z are determined
according to the oxidation number of M).
According to an embodiment of the present invention,
the lithium metal oxide may be lithium titanium oxide, which
is any one selected from the group consisting of Li4Ti5o12,
LiTi2o4, Li2Tio3, and Li2Ti3o7, or a mixture of two or more
thereof, in view of charge and discharge characteristics and
lifetime characteristics required as an anode active material
of the secondary battery.
The lithium metal oxide according to the embodiment of
the present invention may be included in an amount ranging
from 50 wt% to 100 wt% based on a total weight of the anode

active material. The case that the amount of the lithium
metal oxide is 100 wt% based on the total weight of the anode
active material means a case in which the anode active
material is composed of only the lithium metal oxide.
In a secondary battery according to an embodiment of
the present invention, the anode active material may further
include at least one active material selected from the group
consisting of carbon-based materials that are typically used
in an anode active material, transition metal oxides, silicon
(Si)-based materials and Sn-based materials, in addition to
the lithium metal oxide. However, a type of the anode active
material is not limited thereto.
Also, the present invention provides a method of
preparing lithium metal oxide particles having an internal
porosity ranging from 3% to 8% and an average particle
diameter (D50) ranging from 5 µm to 12 µm, including
preparing a precursor solution by adding lithium salt and
metal oxide to a volatile solvent and stirring, providing the
precursor solution into a chamber of a spray dryer, and
spraying the precursor solution in the chamber and drying.
According to an embodiment of the present invention,
the secondary particles of the lithium metal oxide particles
may be formed by a separate granulation process after the
preparation of the primary particles. However, the secondary
particles may be typically prepared by a method of preparing
primary particles and simultaneously agglomerating the
primary particles through a single process. Examples of the
above method may include a spray drying method. Hereinafter,
the method of preparing an anode active material according to
the embodiment of the present invention will be described

using the spray drying method as an example.
According to an embodiment of the present invention,
the metal oxide may be titanium oxide.
Specifically, the method of preparing the lithium metal
oxide particles having an internal porosity ranging from 3%
to 8% and an average particle diameter (D50) ranging from 5
urn to 12 urn of the present invention may include preparing a
precursor solution by adding a lithium salt and titanium
oxide to a volatile solvent and stirring.
More particularly, the lithium salt is dissolved in the
volatile solvent, and the precursor solution may then be
prepared by adding the titanium oxide as the metal oxide
thereto while being stirred.
Herein, the volatile solvent is not particularly
limited so long as it is easily volatile at a spraying
temperature. However, the volatile solvent, for example, may
be water, acetone, or alcohol.
Also, the lithium salt may be a lithium source in a
spray drying process for preparing lithium metal oxide
particles, and may be any one selected from the group
consisting of lithium hydroxide, lithium oxide, and lithium
carbonate or a mixture of two or more thereof. Furthermore,
the titanium oxide may be a titanium source.
The preparation method according to the embodiment of
the present invention may include providing the precursor
solution into a chamber that is included in a spray dryer.
A typically used spray dryer may be used as the above
spray dryer, and for example, an ultrasonic spray dryer, an
air nozzle spray dryer, an ultrasonic nozzle spray dryer, a
filter expansion aerosol generator, or an electrostatic spray

dryer may be used. However, the present xnvention is not
limited thereto.
According to an embodiment of the present invention, a
feed rate of the precursor solution into the chamber may be
in a range of 10 m/min to 1,000 mf/min. In the case that
the feed rate is less than 10 m< /rain, the average particle
diameter of the agglomerated lithium metal oxide particles
may decrease and thus, the formation of the high-density
lithium metal oxide particles may be difficult. In the case
in which the feed rate is greater than 1,000 mf/min, since
the average particle diameter of the lithium metal oxide
particles may relatively increase, realization of desired
high rate characteristics may be difficult.
Furthermore, the preparation method according to the
embodiment of the present invention may include spraying the
precursor solution in the chamber and drying.
The precursor solution may be sprayed through a disc
rotating at a high speed in the chamber and the spraying and
the drying may be performed in the same chamber.
In addition, the internal porosity of the present
invention may be realized by controlling spray drying
conditions, for example, flow of carrier gas, retention time
in a reactor, and internal pressure.
According to an embodiment of the present invention,
the internal porosity of the lithium metal oxide particles
may be controlled by the adjustment of drying temperature,
and the drying may be performed at a temperature ranging from
20°C to 300°C. However, the drying may be performed at a
temperature as low as possible for the high density of the
lithium metal oxide particles.

Also, the average particle diameter of the lithium
metal oxide particles may be controlled by changing a
concentration of a solid content in the precursor solution.
High-density lithium metal oxide particles may be
prepared by performing a heat treatment process on the
prepared precursor using a general sintering furnace at a
temperature between about 700°C and about 850°C for about 5
hours to about 20 hours in an air atmosphere or an oxygen
atmosphere.
The present invention may also provide an anode
including the anode active material, and a lithium secondary
battery including the anode.
An anode current collector is coated with a slurry
which is prepared by mixing an anode slurry including the
anode active material with a solvent, such as N-
methylpyrrolidone (NMP), and the anode may then be prepared
by drying and rolling the anode current collector. The anode
slurry may selectively include a conductive agent, a binder,
or a filler, in addition to the anode active material.
The anode current collector is not particularly limited
so long as it does not generate chemical changes in the
battery as well as having high conductivity. Examples of the
anode current collector may be copper, stainless steel,
aluminum, nickel, titanium, sintered carbon, copper or
stainless steel surface treated with carbon, nickel, titanium,
or silver, aluminum-cadmium alloy, etc. Fine irregularities
may also be formed on a surface of the anode current
collector to increase the adhesion of the anode active
material, and the anode current collector may be used in
various forms, such as a film, sheet, foil, net, porous body,

foam, or nonwoven fabric.
The conductive agent may be typically added in an
amount ranging from 1 wt% to 30 wt% based on a total weight
of a mixture including the anode active material. The
conductive agent is not particularly limited so long as it
does not generate chemical changes in the battery as well as
having conductivity. Examples of the conductive agent may be
graphite such as natural graphite and artificial graphite;
carbon black such as acetylene black, Ketjen black, channel
black, furnace black, lamp black, and thermal black;
conductive fibers such as carbon fibers and metal fibers;
metal powder such as fluorocarbon powder, aluminum powder and
nickel powder; conductive whiskers such as zinc oxide
whiskers and potassium titanate whiskers; conductive metal
oxide such as titanium oxide; a conductive material such as a
polyphenylene derivative, etc.
The binder is a component that assists in bonding
between the active material and the conductive agent and
bonding with respect to the current collector, and the binder
may be typically added in an amount ranging from 1 wt% to 30
wt% based on the total weight of the mixture including the
anode active material. Examples of the binder may be
polyvinylidene fluoride (PVdF), polyvinyl alcohol,
carboxymethyl cellulose (CMC), starch, hydroxypropyl
cellulose, regenerated cellulose, polyvinylpyrrolidone,
tetrafluoroethylene, polyethylene, polypropylene, ethylene-
propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-
butadiene rubber, fluorine rubber, various copolymers, etc.
The filler is selectively used as a component that
prevents the expansion of the anode and is not particularly

limited so long as it does not generate chemical changes in
the battery as well as being a fibrous material. Examples of
the filler may be olefin-based polymers such as polyethylene
and polypropylene; and fibrous materials such as glass fibers
and carbon fibers.
A method of uniformly coating the anode current
collector with the anode slurry may be selected from known
methods in consideration of material characteristics or may
be performed by a new appropriate method. For example, a
paste is distributed on the current collector, and the paste
is then uniformly dispersed by using a doctor blade. In some
cases, a method of performing the distribution and dispersion
processes in a single process may also be used. In addition,
a method, such as die casting, comma coating, and screen
printing, may be selected, or the anode slurry may be molded
on a separate substrate and the molded anode slurry may then
be bonded with the current collector by pressing or
lamination.
For example, a cathode current collector is coated with
a cathode slurry including a cathode active material, and the
cathode may then be prepared by drying the cathode current
collector. The cathode slurry, if necessary, may include the
above-described components.
In particular, as the cathode active material, the
lithium secondary battery may use a layered compound, such as
lithium cobalt oxide (LiCoO2) or lithium nickel oxide
(LiNiO2) , or a compound substituted with one or more
transition metals; lithium manganese oxides such as Li1+X Mn2-
xO4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, and LiMnO2;
lithium copper oxide (Li2CuO2) ; vanadium oxides such as LiV3O8,

LiFe3O4, V2O5, and Cu2V2O7; Ni-site type lithium nickel oxides
expressed by a chemical formula of LiNi1-xMxO2 (where M is
cobalt (Co) , manganese (Mn) , Al, Cu, Fe, magnesium (Mg) ,
boron (B) , or gallium (Ga) , and x is 0.01 to 0.3); lithium
manganese complex oxides expressed by a chemical formula of
LiMn2-xMxO2 (where M is Co, nickel (Ni) , Fe, chromium (Cr) , Zn,
or tantalum (Ta), and x is between 0.01 and 0.1) or Li2Mn3MO8
(where M is Fe, Co, Ni, Cu, or Zn) ; LiMn204 having a part of
Li substituted with alkaline earth metal ions; a disulfide
compound; or Fe2 (M0O4) 3. However, LiNixMn2-xO4 (where x is 0.01
to 0.6) may be used, and for example, LiNi0.5Mn1.5O4 or
LiNi0.4Mn1.6O4 may be used. That is, in the present invention,
spinel lithium manganese complex oxide of LiNixMn2_x04 (where
x is 0.01 to 0.6) having relatively high potential due to the
high potential of the anode active material may be used as
the cathode active material.
Any battery case typically used in the art may be
selected as a battery case used in the present invention. A
shape of the lithium secondary battery according to the use
thereof is not limited, and for example, a cylindrical type
using a can, a prismatic type, a pouch type, or a coin type
may be used.
The lithium secondary battery according to the present
invention may not only be used in a battery cell that is used
as a power source of a small device, but may also be used as
a unit cell in a medium and large sized battery module
including a plurality of battery cells.
Preferred examples of the medium and large sized device
may be an electric vehicle, a hybrid electric vehicle, a
plug-in hybrid electric vehicle, or a power storage system,

but the medium and large sized device is not limited thereto.
Hereinafter, the present invention will be more fully-
described according to specific embodiments. The present
invention may, however, be embodied in many different forms
and should not be construed as being limited to the
embodiments set forth herein.
Examples
Example 1: Preparation of Li4TisOi2 having an average
particle diameter of 5.4 um and an internal porosity of 3.5%
LiOH-H20 and Ti02 (anatase) were mixed at a molar ratio
of 4:5. A mixture was dissolved in pure water and a solution
was then stirred. In this case, a ratio of a total solid
material is defined as a solid content of the solution, and a
precursor solution was prepared by adjusting the solid
content to 30% and stirring. The precursor solution was
provided into a chamber of a spray dryer (by EIN SYSTEMS, Co.,
Ltd.). Then, the precursor solution was sprayed in the
chamber and dried. The spray drying were performed under
conditions including a drying temperature of 130°C, an
internal pressure of -20 mbar, and a feed rate of 30 ml/min,
and a Li4Ti50i2 anode active material having an average
particle diameter of 5.4 urn and an internal porosity of 3.5%
was then obtained by sintering the precursor thus obtained at
800°C in air.
Examples 2 to 4: Preparation of Li4Ti5Oi2
Li4Ti50i2 anode active materials having average particle
diameters and internal porosities listed in Table 1 were

obtained in the same manner as Example 1 except that spraying
conditions listed in the following Table 1 were changed.
Comparative Examples 1 to 5: Preparation of Li4Ti5Oi2
Li4Ti50i2 anode active materials having average particle
diameters and internal porosities listed in Table 1 were
obtained in the same manner as Example 1 except that the
spraying conditions listed in the following Table 1 were
changed.

1. Average particle diameter: laser diffraction method
(Microtac MT 3000)
2. Internal porosity = volume of pores per unit
mass/(specific volume + volume of pores per unit mass) (use

BELSORP (BET instrument) by BEL Japan Inc., use values
calculated by the Barrett-Joyner-Halenda (BJH) method, i.e.,
a mesopore measurement method)
Examples 5 to 8: Lithium Secondary Battery Preparation

Li4Ti5O12 of Examples 1 to 4 listed in Table 1 as an
anode active material, carbon black (Super P) as a conductive
agent, and PVdF as a binder were mixed at' a weight ratio of
88:4:8, and the mixture was then added to N-methyl-2-
pyrrolidone as a solvent to prepare a slurry. One surface of
a copper current collector was coated with the prepared
slurry to a thickness of 65 um, and then dried and rolled.
Then, anodes were prepared by punching into a predetermined
size.

Ethylene carbonate (EC) and diethyl carbonate (DEC)
were mixed at a volume ratio of 30:70 to prepare a non-
aqueous electrolyte solvent, and LiPF6 was added thereto to
prepare a 1 M LiPF6 non-aqueous electrolyte solution.
Also, a lithium foil was used as a counter electrode,
i.e., a cathode, and a polyolefin separator was disposed
between both electrodes. Then, coin-type half cells were
prepared by injecting the electrolyte solution.
Comparative Examples 6 to 10: Lithium Secondary Battery
Preparation
Lithium secondary batteries were prepared in the same
manner as Example 5 except that Li4Ti5O12 of Comparative

Examples 1 to 5 listed in Table 1 were used as an anode
active material.
Experimental Example 1

Lithium metal oxide anode active materials prepared in
Comparative Example 3 and Example 1 were respectively-
identified by scanning electron microscope (SEM) micrographs,
and the results thereof are respectively presented in FIGS. 1
and 2.
FIG. 1 is a SEM micrograph of Li4Ti5O12 having an
average particle diameter of 6.5 urn and an internal porosity
of 15%, wherein it may be confirmed that the Li4Ti5O12 was
composed of porous secondary particles in which pores were
formed on the surface and inside of the secondary particle
due to the agglomeration of primary particles. In this case,
black regions in the particle represent pores.
With respect to FIG. 2, primary particles were
agglomerated to constitute a secondary particle, and a SEM
micrograph of Li4Ti5O12 having an average particle diameter of
5.4 µm and an internal porosity of 3.5% is illustrated. It
may be visually confirmed that the Li4Ti5O12 of Example 1 had
higher density than the Li4Ti5O12 of Comparative Example 3.
Experimental Example 2

In order to analyze high rate characteristics of the
lithium secondary batteries of Examples 5 to 8 and
Comparative Examples 6 to 10, the high rate characteristics
of the lithium secondary batteries were evaluated by
sequentially changing charge and discharge rates to 0.1 C,
0.2 C, 0.5 C, 1 C, 0.2C, 2 C, 0.2C, 5 C, 0.2C, and 10 C,
respectively. In this case, a charge end voltage was set as
1.0 V and a discharge end voltage was set as 2.5 V. The high
rate characteristics for each lithium secondary battery were
expressed as a percentage value of a capacity measured at 10C
with respect to a capacity at 0.1 C.
The results thereof are presented in Table 2 below.



As illustrated in Table 2, in the case that Li4Ti5O12
particles had similar average particle diameters, it may be
confirmed that there were differences in the adhesion to the
electrode due to the differences in the internal porosity of
the lithium metal oxide particles and furthermore, the high
rate characteristics were affected. The reason for this may
be understood in the following way: in the case in which the
internal porosity of the lithium metal oxide particles
increased, the binder may be introduced into pores in the
lithium metal oxide particles to loosen the connection
between the anode active material and the conductive agent,
and thus, electrode resistance may increase. As a result,
the high rate characteristics may degrade.
Also, in the case that the internal porosity of the
lithium metal oxide particles was relatively low, since the
penetration of the electrolyte solution into the active
material was not facilitated, it may cause the degradation of
the high rate characteristics despite high adhesion.
In addition, with respect to the lithium metal oxide
particles having similar internal porosities, it may be
confirmed that electrode adhesion and high rate
characteristics were different due to the differences in
particle diameters thereof. It may be interpreted as the
result of the reduction of the electrode adhesion when the
particle diameter was relatively small.
In the case that the diameter of the lithium metal
oxide particle was large, it may be understood that the high

rate characteristics may decrease due to the decrease in the
electrical conductivity of the active material in the lithium
metal oxide particles.
Therefore, it may be confirmed that the balance between
the internal porosity of the lithium metal oxide particles
and the average particle diameter of the lithium metal oxide
particles was required to improve the high rate
characteristics.
INDUSTRIAL APPLICABILITY
As described above, an anode active material according
to the technical idea of the present invention includes high-
density lithium metal oxide particles, and thus, the adhesion
to an anode may be significantly improved. That is, an
amount of a binder required to obtain the same strength of
adhesion to the electrode may be significantly reduced in
comparison to a typical anode active material having a
typical density.
High-density lithium metal oxide particle may be formed
as the internal porosity of the lithium metal oxide particles
decreases. As a result, the amount of the binder required to
prepare an anode slurry may be reduced, and thus, it is
advantageous for the mass production of secondary batteries.
Since the realization of the high-density lithium metal
oxide and the resultant good adhesion to the electrode may be
possible, an average particle diameter of the lithium metal
oxide particles may be further decreased. As a result, high
rate characteristics of the secondary battery may be improved.

CLAIMS
1. An anode active material comprising lithium metal
oxide particles,
wherein an internal porosity of the lithium metal oxide
particles is in a range of 3% to 8% and an average particle
diameter (D50) thereof is in a range of 5 µm to 12 urn.
2. The anode active material of claim 1, wherein the
lithium metal oxide is a compound expressed by LixMyOZ (where
M is at least one element independently selected from the
group consisting of titanium (Ti), tin (Sn), copper (Cu) ,
lead (Pb), antimony (Sb), zinc (Zn), iron (Fe), indium (In),
aluminum (Al) , or zirconium (Zr) ; and x, y, and z are
determined according to an oxidation number of M.
3. The anode active material of claim 1, wherein the
lithium metal oxide is any one selected from the group
consisting of Li4Ti5O12, LiTi2O4, Li2TiO3, and Li2Ti3O7, or a
mixture of two or more thereof.
4. The anode active material of claim 1, wherein the
lithium metal oxide particle is a secondary particle, in
which two or more primary particles are agglomerated.
5. The anode active material of claim 4, wherein an
average particle diameter of the primary particles is in a
range of 100 nm to 400 nm.
6. The anode active material of claim 1, wherein a

specific surface area (Brunauer-Emmett-Teller (BET)) of the
lithium metal oxide particles is in a range of 2 m2/g to 8
m2/g.
7. A method of preparing lithium metal oxide
particles having an internal porosity ranging from 3% to 8%
and an average particle diameter (D50) ranging from 5 µm to
12 µm, the method comprising:
preparing a precursor solution by adding a lithium salt
and a metal oxide to a volatile solvent and stirring;
providing the precursor solution into a chamber of a
spray dryer; and
spraying the precursor solution in the chamber and
drying.
8. The method of claim 7, wherein the lithium salt
is any one selected from the group consisting of lithium
hydroxide, lithium oxide, and lithium carbonate, or a mixture
of two or more thereof.
9. The method of claim 7, wherein the metal oxide is
titanium oxide.

10. The method of claim 7, wherein the volatile
solvent is water, alcohol, or acetone.
11. The method of claim 7, wherein a feed rate of the
precursor solution into the chamber is in a range of 10
mℓ/min to 1,000 mℓ/min.

12. The method of claim 7, wherein the drying is
performed at a temperature ranging from 20°C to 300°C.
13. An anode comprising the anode active material of
claim 1.
14. A secondary battery comprising the anode of claim
13.