U.S. patent application number 15/669578 was filed with the patent office on 2017-11-23 for compositions and methods for manufacturing a cathode for lithium secondary battery.
The applicant listed for this patent is Hyundai Motor Company, Korea Electronics Technology Institute. Invention is credited to Woo Suk Cho, Dong Gun Kim, Dong Jin Kim, Jeom Soo Kim, Sa Heum Kim, Young Jun Kim, Jun Ho Song.
Application Number | 20170334724 15/669578 |
Document ID | / |
Family ID | 47879776 |
Filed Date | 2017-11-23 |
United States Patent
Application |
20170334724 |
Kind Code |
A1 |
Kim; Dong Gun ; et
al. |
November 23, 2017 |
COMPOSITIONS AND METHODS FOR MANUFACTURING A CATHODE FOR LITHIUM
SECONDARY BATTERY
Abstract
Disclosed are compositions and methods for producing a cathode
for a secondary battery, where lithium manganese fluorophosphate
such as Li.sub.2MnPO.sub.4F can be used as an electrode material.
Li.sub.2MnPO.sub.4F is prepared by chemical intercalation of
lithium, and can be used as an electrode material, and a
non-lithium containing material can then be used as an anode
material for manufacturing of a full cell Furthermore, it is
possible to provide a carbon coating for a cathode material for a
lithium battery, which has improved electrical conductivity.
Inventors: |
Kim; Dong Gun; (Gunpo,
KR) ; Kim; Sa Heum; (Gwacheon, KR) ; Kim;
Young Jun; (Yongin, KR) ; Song; Jun Ho;
(Seongnam, KR) ; Cho; Woo Suk; (Namyangju, KR)
; Kim; Jeom Soo; (Hwaseong, KR) ; Kim; Dong
Jin; (Namyangju-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hyundai Motor Company
Korea Electronics Technology Institute |
Seoul
Seongnam |
|
KR
KR |
|
|
Family ID: |
47879776 |
Appl. No.: |
15/669578 |
Filed: |
August 4, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13314049 |
Dec 7, 2011 |
9725321 |
|
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15669578 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C01B 25/455 20130101;
H01M 4/5825 20130101; H01M 4/1395 20130101; H01M 4/136 20130101;
Y02E 60/10 20130101 |
International
Class: |
C01B 25/455 20060101
C01B025/455; H01M 4/136 20100101 H01M004/136; H01M 4/1395 20100101
H01M004/1395; H01M 4/58 20100101 H01M004/58 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 21, 2011 |
KR |
10-2011-0095448 |
Claims
1. A cathode composition for a secondary battery, comprising a
lithium manganese-based fluorophosphate compound of formula
Li.sub.2MnPO.sub.4F
2. The cathode composition of claim 1, wherein the compound of
formula Li.sub.2MnPO.sub.4F has a primary particle size of about
300 nm or less.
3. The cathode composition of claim 1, wherein the compound of
formula Li.sub.2MnPO.sub.4F is coated with carbon.
4. The cathode composition of claim 3, wherein the coated compound
of formula Li.sub.2MnPO.sub.4F shows a potential plateau by
discharge of about 3.7 V to about 4.0V, and a discharge capacity of
about 100 mAhg.sup.-1 or more at discharge of about 2.0 V, and a
discharge capacity of about 200 mAhg.sup.-1 or more at discharge of
about 1.0 V.
5-16. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims under 35 U.S.C. .sctn.119(a) the
benefit of Korean Patent Application No. 10-2011-0095448 filed on
Sep. 21, 2011, the entire contents of which are incorporated herein
by reference.
BACKGROUND
(a) Technical Field
[0002] The present invention relates to compositions and methods
for manufacturing a cathode for a secondary battery. More
particularly, it relates to compositions and methods for
manufacturing a cathode for a secondary battery, where lithium
manganese fluorophosphate (Li.sub.2MnPO.sub.4F) can be used as an
electrode material.
(b) Background Art
[0003] As the use of portable small-sized electronic devices has
become widespread, there has been an active interest in developing
new types of, secondary batteries such as nickel metal hydrogen or
lithium secondary batteries. For example, a lithium secondary
battery uses carbon (such as, e.g., graphite) as an anode
composition, lithium-containing oxide as a cathode active material,
and a non-aqueous solvent as an electrolyte. Lithium is a metal
that has a very high tendency to undergo ionization; consequently,
lithium can achieve a high voltage. Thus, lithium is often used in
the development of batteries having high energy density.
[0004] In a lithium battery, a cathode composition typically
includes a lithium transition metal oxide containing lithium in
which 90% or more of the lithium transition metal oxide includes
layered lithium transition metal oxides (such as, e.g.,
cobalt-based, nickel-based, cobalt/nickel/manganese ternary-based,
and the like). However, when such layered lithium transition metal
oxides are used as a cathode material, lattice oxygen within the
layered lithium transition metal oxides may become deintercalated
and participate in an undesired reaction under non-ideal conditions
(such as, e.g., overcharge and high temperature), thereby causing
the battery to catch fire or explode.
[0005] In order to overcome the disadvantages of such layered
lithium transition metal oxides, researchers have considered
cathode compositions having a spinel or olivine structure.
[0006] In particular, it has been suggested that a cathode
composition including a spinel-based lithium manganese oxide having
a three dimensional lithium movement path, or a polyanion-based
lithium metal phosphate having an olivine structure, instead of a
layered lithium transition metal oxide, may prevent problems in
lithium secondary batteries that arise from decreased stability in
layered lithium transition metal oxides as a result of cathode
deterioration. However, the use of the spinel-based lithium
manganese oxide as a cathode material has been limited because
repeated cycles of battery charging and discharging result in
lithium elution. Moreover, spinel-based lithium manganese oxide
containing compositions display structural instability as a result
of the Jahn-Teller distortion effect.
[0007] The use of olivine-based lithium metal phosphates, such as
iron (Fe)-based phosphate and manganese (Mn)-based phosphate, as a
cathode material has also been limited because these compounds have
low electrical conductivity. However, through the use of nano-sized
particles and carbon coating, the problem of low electrical
conductivity has been improved, and thus the use of olivine-based
lithium metal phosphates as a cathode material has become
possible.
[0008] For example, it has been recently reported that
fluorophosphates may be useful as a cathode material. The
fluorophosphate has the following formula: A.sub.2MPO.sub.4F, where
A represents Li or Na, and M represents a transition metal such as
Mn, Fe, Co, Ni, V, or a mixture thereof. Theoretically, the
fluorophosphate of formula A.sub.2MPO.sub.4F is expected to have a
capacity about twice as high as a conventional lithium metal
phosphate since it has two Na atoms. For example, in the case where
a fluorophosphate having the formula Na.sub.2MPO.sub.4F (where M
equals Mn, Fe, Co, Ni, V, or a mixture thereof) is used as a
cathode material for a lithium secondary battery, sodium is
deintercalated during the initial charge, lithium is intercalated
during an initial discharge, and then in following cycles of
battery charging and discharging, alternating, intercalation and
deintercalation of lithium occurs during the charging and
discharging process. Similarly, in the case where
Na.sub.2MPO.sub.4F (M=Mn, Fe, Co, Ni, V or a mixture thereof) is
used as a cathode material for a sodium battery, the intercalation
and deintercalation of sodium is carried out during charging and
discharging.
[0009] U.S. Pat. No. 6,872,492 discloses an example of using a
fluorophosphate including sodium, such as NaVPO.sub.4F,
Na.sub.2FePO.sub.4F, or (Na,Li).sub.2FePO.sub.4F, as a cathode
material for a sodium based battery. However, the example is
limited to a sodium based battery, and has not been attempted for a
lithium battery.
[0010] As another example of the conventional art, sodium iron
fluorophosphate (Na.sub.2FePO.sub.4F) has been used as a cathode
material for a lithium secondary battery, and the structure of
Na.sub.2FePO.sub.4F and its electrochemical characteristics have
been disclosed. However, iron-based Na.sub.2FePO.sub.4F suffers
from a major disadvantage as a cathode material because it has a
low charge/discharge potential (about 3.5 V) which is similar to an
iron-based olivine material. Attempts to overcome this disadvantage
of Na.sub.2FePO.sub.4F have been made by using, manganese-based
Na.sub.2MnPO.sub.4F, which has a higher potential (4V) compared to
iron-based Na.sub.2FePO.sub.4F. Unfortunately, Na.sub.2MnPO.sub.4F
also suffers from a major disadvantage as a cathode material
because of electrochemical inactivity due to the low electrical
conductivity of a polyanion-based material.
[0011] When a lithium ion battery is manufactured as a full cell, a
graphite-based material is generally used as an anode material.
Unlike lithium metal, the graphite-based material does not include
lithium, and thus a lithium source is generally provided from the
cathode. Na.sub.xMnPo.sub.4F including only sodium does not include
lithium, and thus does not provide lithium ions required for an
intercalation reaction of lithium. Thus, in this case, it is
impossible to apply a graphite-based anode material. Accordingly,
when Na.sub.xMnPo.sub.4F is used as a cathode material for a
lithium ion battery, there is a limitation in the selection of an
anode material. It is known in the conventional art that it is
impossible to directly synthesize manganese fluorophosphate
including lithium, and there is no report on such a synthesis.
According to conventional reports, the preparation of lithium
manganese fluorophosphate Li.sub.2MnPO.sub.4F was carried out by an
ion exchange of sodium deintercalation/lithium intercalation
through a chemical method. However, due to the lack of chemical
reactivity of Li.sub.2MnPO.sub.4F, the intercalation of lithium has
not been shown. This may be caused by the fact that sodium
manganese fluorophosphate has a low chemical reactivity.
[0012] The systems and methods of the present invention have other
features and advantages which will be apparent from or are set
forth in more detail in the accompanying drawings, which are
incorporated herein, and the following Detailed Description of the
Invention, which together serve to explain certain principles of
the present invention.
SUMMARY OF THE DISCLOSURE
[0013] The present invention provides a solution for the
above-described problems associated with the prior art. The present
invention provides lithium manganese fluorophosphate
(Li.sub.2MnPO.sub.4F) as a novel electrode material. According to
the exemplary embodiment of the invention, Li.sub.2MnPO.sub.4F is
prepared by introducing Li into Na.sub.2MnPO.sub.4F by a chemical
method. Accordingly, an object of the present invention is to
provide compositions and methods of manufacturing a cathode for a
secondary battery, where an anode material not including a lithium
source can be used for manufacturing a lithium ion secondary
battery.
[0014] In one aspect, the present invention provides a composition
for cathode material for a secondary battery cathode that includes
a compound represented by the formula Li.sub.2MnPO.sub.4F, which is
prepared by chemical intercalation of lithium into
Na.sub.2MnPO.sub.4F.
[0015] In another aspect, the present invention provides a method
for preparing a cathode for a secondary battery, the method
including:
[0016] (i) uniformly mixing sodium (Na) oxide, or a precursor
thereof, manganese(Mn) oxide, or a precursor thereof, phosphate
(P), or a precursor thereof, and fluoride (F), or a precursor
thereof, by ball milling, and carrying out pretreatment on the
resulting mixture, followed by firing so as to synthesize the
cathode material Na.sub.2MnPO.sub.4F; and
[0017] (ii) intercalating lithium into the cathode material
synthesized from step (i) through an ion exchange method so as to
synthesize Li.sub.2MnPO.sub.4F.
[0018] As set forth above, the present invention makes it is
possible to provide lithium manganese fluorophosphate including a
lithium source as a cathode material because lithium is chemically
intercalated through an ion exchange method, and when the inventive
cathode material is applied to the cathode of a secondary battery,
it is possible to achieve a high discharge voltage of about 3.8 V
(Li/Li.sup.+).
[0019] Other aspects and exemplary embodiments of the invention are
discussed infra.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The above and other features of the present invention will
now be described in detail with reference to certain exemplary
embodiments thereof illustrated in the accompanying drawings which
are given hereinbelow by way of illustration only, and thus are not
limitative of the present invention, and wherein:
[0021] FIG. 1A shows an electron microscopic image of a cathode
material prepared by the method of Example 1 of the present
invention before ion exchange treatment;
[0022] FIG. 1B shows an electron microscopic image of a cathode
material prepared by the method of Example 1 of the present
invention after ion exchange treatment;
[0023] FIG. 2 shows charge/discharge curve graphs of a battery
including the cathode material prepared according to the method of
Example 1, at room temperature, at a discharge cut-off voltage of
2.0 V;
[0024] FIG. 3 shows charge/discharge curve graphs of a battery
including the cathode material prepared according to the method of
Example 1, at room temperature, at a discharge cut-off voltage of
1.0 V; and
[0025] FIG. 4 shows the discharge curve graphs of a battery
including the cathode material prepared according to the method of
Example 1, at a high temperature (60.degree. C.).
[0026] It should be understood that the appended drawings are not
necessarily to scale, presenting a somewhat simplified
representation of various preferred features illustrative of the
basic principles of the invention. The specific design features of
the present invention as disclosed herein, including, for example,
specific dimensions, orientations, locations, and shapes will be
determined in part by the particular intended application and use
environment.
DETAILED DESCRIPTION
[0027] Hereinafter reference will now be made in detail to various
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings and described below. While
the invention will be described in conjunction with exemplary
embodiments, it will be understood that the present description is
not intended to limit the invention to those exemplary embodiments.
On the contrary, the invention is intended to cover not only the
exemplary embodiments, but also various alternatives,
modifications, equivalents and other embodiments, which may be
included within the spirit and scope of the invention as defined by
the appended claims.
[0028] Unless specifically stated or obvious from context, as used
herein, the term "about" is understood as within a range of normal
tolerance in the art, for example within 2 standard deviations of
the mean. "About" can be understood as within 10%, 9%, 8%, 7%, 6%,
5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated
value. Unless otherwise clear from the context, all numerical
values provided herein are modified by the term "about."
[0029] Ranges provided herein are understood to be shorthand for
all of the values within the range. For example, a range of 1 to 50
is understood to include any number, combination of numbers, or
sub-range from the group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9,
10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26,
27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43,
44, 45, 46, 47, 48, 49, or 50, as well as all intervening decimal
values between the aforementioned integers such as, for example,
1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9.
[0030] The present invention provides a cathode material for a
secondary battery, which includes a lithium manganese-based
fluorophosphate compound represented by the following Formula:
Li.sub.2MnPO.sub.4F.
[0031] The cathode material for a secondary battery, which includes
the Formula above, has a primary particle size of about 300 nm or
less, is coated with carbon for improvement of conductivity, and
shows a potential plateau by discharge at about 3.7 V to about
4.0V, and a discharge capacity of about 100 mAhg.sup.-1 or more at
discharge of about 2.0 V, and a discharge capacity of about 200
mAhg.sup.-1 or more at discharge of about 1.0 V.
[0032] The present invention provides a method for producing a
cathode material for a secondary battery, the method including:
[0033] (i) uniformly mixing sodium (Na) oxide or a precursor
thereof, manganese(Mn) oxide or a precursor thereof, phosphate (P)
or a precursor thereof, and fluoride (F) or a precursor thereof
through ball milling, and carrying out pretreatment on the obtained
mixture, followed by firing so as to synthesize a cathode material
Na.sub.2MnPO.sub.4F; and
[0034] (ii) intercalating lithium into the cathode material
synthesized in step (i) through an ion exchange method so as to
synthesize Li.sub.2MnPO.sub.4F.
[0035] According to a preferred embodiment of the present
invention, in step (i), the mixture is uniformly mixed for 6 hours
by ball milling, and then subjected to pretreatment under an air
atmosphere at 300.degree. C. for 2 hours.
[0036] According to a preferred embodiment of the present
invention, step (ii) includes the step of intercalating lithium
ions into the cathode material obtained from step (i) through
lithium intercalation/sodium deintercalation by an ion exchange
method.
[0037] According to a preferred embodiment of the present
invention, step (ii) includes the step of chemically
deintercalating sodium from the cathode material obtained from step
(i), and chemically intercalating lithium into the cathode
material.
[0038] According to a preferred embodiment of the present
invention, the cathode material obtained from step (ii) is
uniformly mixed with a carbon conductive material at a ratio of
about 60:40 to about 90:10, followed by ball milling It is
contemplated within the scope of the invention that the
aforementioned range includes all sub-ranges within the specified
range. For example, the ratio of cathode material to carbon
conductive material may range from about 60:40 to about 61:39,
62:38, 63:37, 64:36, 65:35, 66:34, 67:33, 68:32, 69:31, 70:30,
71:29, 72:28, 73:27, 74:26, 75:25, 76:24, 77:23, 78:22, 79:21,
80:20, 81:19, 82:18, 83:17, 84:16, 85:15, 86:14, 87:13, 88:12,
89:11, or 90:10. Similarly, the ratio of cathode material to carbon
conductive material may range from about 90:10 to about 89:11,
88:12, 87:13, 86:14, 85:15, 84:16, 83:17, 82:18, 81:19, 80:20,
79:21, 78:22, 77:23, 76:24, 75:25, 74:26, 73:27, 72:28, 71:29,
70:30, 69:31, 68:32, 67:33, 66:34, 65:35, 64:36, 63:37, 62:38,
61:39, or 60:40. It is further contemplated within the scope of the
invention that the ratio of cathode material to carbon conductive
material may include all intervening ratios, for example, about
60:40, about 61:39, about 62:38, about 63:37, about 64:36, about
65:35, about 66:34, about 67:33, about 68:32, about 69:31, about
70:30, about 71:29, about 72:28, about 73:27, about 74:26, about
75:25, about 76:24, about 77:23, about 78:22, about 79:21, about
80:20, about 81:19, about 82:18, about 83:17, about 84:16, about
85:15, about 86:14, about 87:13, about 88:12, about 89:11, and
about 90:10, as well as all intervening decimal values. Then, the
carbon conductive material is uniformly coated on a cathode surface
so as to improve the electric conductivity.
[0039] The precursor of the sodium oxide may be selected from
sodium phosphate, sodium carbonate, sodium hydroxide, sodium
acetate, sodium sulfate, sodium sulfite, sodium fluoride, sodium
chloride, sodium bromide, and any mixture thereof.
[0040] The precursor of the manganese oxide may be selected from
manganese metal, manganese oxide, manganese oxalate, manganese
acetate, manganese nitrate, and any mixture thereof.
[0041] The precursor of phosphate may be selected from ammonium
phosphate, sodium phosphate, potassium phosphate, and any mixture
thereof.
[0042] Furthermore, LiBr or LiI may be used to cause ion exchange
between lithium and sodium during the intercalation of lithium by
the ion exchange method.
[0043] Hereinafter, the present invention will be described in more
detail with reference to the accompanying drawings.
[0044] The present invention provides a cathode material for a
secondary battery, which includes a compound represented by the
Formula:
Li.sub.2MnPO.sub.4F.
[0045] In the exemplary embodiment of the present invention, the
cathode material shows a potential discharge plateau from about 3.7
V to about 4.0V, and is coated with carbon for conductivity
improvement.
[0046] Hereinafter, the method for producing a cathode material for
a secondary battery, according to the present invention will be
described. The specific production method will be more easily
understood through the following Examples.
[0047] For example, the cathode material Na.sub.2MnPO.sub.4F for a
secondary battery is prepared by uniformly mixing sodium oxide or a
precursor thereof, manganese oxide or a precursor thereof,
phosphate or a precursor thereof, and fluoride or a precursor
thereof through ball milling, carrying out pretreatment on the
mixture, followed by firing so as to synthesize a cathode material
Na.sub.2MnPO.sub.4F; and carrying out heat treatment by firing the
mixture obtained from the pretreatment step. According to the
invention, the prepared Na.sub.2MnPO.sub.4F has a particle size of
about 1 .mu.m or less, and an average particle size of about 300
nm. Na.sub.2MnPO.sub.4F prepared according to the invention is
introduced into an acetonitrile solution including, for example,
LiBr dissolved therein. Then, Argon gas is flowed into the solution
while the reaction temperature is raised so that ion exchange
between lithium and sodium can be carried out. By washing and
drying the resulting product of the ion exchange, a cathode
material, lithium fluorophosphate Li.sub.2MnPO.sub.4F, is
obtained.
[0048] In order to increase electrical conductivity, the obtained
cathode material, Li.sub.2MnPO.sub.4F, was subjected to carbon
coating.
[0049] The precursor of the sodium oxide may be any suitable sodium
containing compound including, but not particularly limited to,
sodium phosphate, sodium carbonate, sodium hydroxide, sodium
acetate, sodium sulfate, sodium sulfite, sodium fluoride, sodium
chloride, sodium bromide, and any mixture thereof.
[0050] The precursor of the manganese oxide may be any suitable
manganese containing compound including, but not particularly
limited to, manganese metal, manganese oxide, manganese oxalate,
manganese acetate, manganese nitrate, and any mixture thereof.
[0051] The precursor of phosphate may be any suitable phosphate
containing compound including, but not particularly limited to,
lithium phosphate, sodium phosphate, potassium phosphate and any
mixture thereof.
[0052] The precursor of fluorine may be any suitable fluorine
containing compound including, but not particularly limited to,
metal fluoride, fluoride, and a mixture thereof. The lithium source
used for the ion exchange may be any suitable lithium containing
compound including, but not particularly limited to, LiBr, LiI, or
any lithium compound mixture suitable for causing ion exchange.
[0053] The solvent used for the ion exchange may be any solvent
suitable for including, but not limited to, acetonitrile. The
carbon conductive material may be, but is not particularly limited
to, citric acid, sucrose, super-P, acetylene black, Ketchen Black,
or any suitable carbon material.
[0054] The cathode material of the exemplary embodiment of the
present invention prepared as described above may be used for
manufacturing a lithium secondary battery. Herein, the
manufacturing method is the same as that of a conventional lithium
secondary battery manufacturing method except for the application
of the cathode material. Hereinafter, the configuration and the
manufacturing method of the secondary battery will be briefly
described.
[0055] First, in a manufacturing process for a cathode plate using
the inventive cathode material, the cathode material is added with
one, two, or more kinds of conventionally used additives, such as,
for example, a conductive material, a binding agent, a filler, a
dispersing agent, an ion conductive material, and a pressure
enhancer, as required, and the mixture is formed into a slurry or
paste with an appropriate solvent (such as, e.g., an organic
solvent). Then, the obtained slurry or paste is applied to an
electrode supporting substrate by an appropriate technique such as,
for example, the "doctor blade" method, etc., and then dried. Then,
through pressing by rolling a roll, a final cathode plate is
manufactured.
[0056] According to an exemplary embodiment of the invention,
examples of the conductive material include graphite, carbon black,
acetylene black, Ketchen Black, carbon fiber, metal powder, and the
like. The binding agent may include, but is not limited to, PVdF,
polyethylene, and the like. The electrode supporting substrate
(collector) may include, but is not limited to, a foil or a sheet
of copper, nickel, stainless steel, aluminum, carbon fiber, and the
like.
[0057] By using the cathode plate prepared as described above, a
lithium secondary battery is manufactured. The lithium secondary
battery may be manufactured into a variety of different shapes
including, but not limited to, a coin shape, a button shape, a
sheet shape, a cylindrical shape, or a square shape. Also, an
anode, an electrolyte, and a separator for the lithium secondary
battery are the same as those used in a conventional lithium
secondary battery.
[0058] The anode material may be a graphite-based material that
does not include lithium. Additionally, the anode material may also
include one, two, or more kinds of transition metal composite
oxides including lithium. The anode material may also include
silicon, tin, etc.
[0059] The electrolyte may be, but is not limited to, a non-aqueous
electrolyte including lithium salt dissolved in an organic solvent,
an inorganic solid electrolyte, or a composite of an inorganic
solid electrolyte. The solvent for the non-aqueous electrolyte may
be, but is not limited to, one, two, or more solvents selected from
the group of esters (such as, e.g., ethylene carbonate, propylene
carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl
carbonate), lactones (such as, e.g., butyl lactone), ethers (such
as, e.g., 1,2-dimethoxy ethane, ethoxy methoxy ethane), or nitriles
(such as, e.g., acetonitrile). Examples of lithium salt of the
non-aqueous electrolyte may include, but is not limited to,
LiAsF.sub.6, LiBF.sub.4, LiPF.sub.6, or the like.
[0060] Also, as the separator, a porous film prepared from a
polyolefin such as, for example, PP and/or PE, or a porous material
such as non-woven fabric may be used.
EXAMPLES
[0061] Hereinafter, the following examples are provided to further
illustrate the invention, but they should not be considered as the
limit of the invention. The following examples illustrate the
invention and are not intended to limit the same.
Example 1
[0062] Sodium carbonate (Na.sub.2CO.sub.3), manganese
oxalate.hydrate (MnC.sub.2O.sub.4.2H.sub.2O), sodium fluoride
(NaF), sodium hydrogen carbonate (NaHCO.sub.3), and ammonium
phosphate (NH.sub.4H.sub.2PO.sub.4) were introduced in
predetermined amounts with respect to the total amount of 10 g, and
ball milled for 6 hours so as to uniformly the materials.
[0063] The resulting mixture was subjected to pretreatment at
300.degree. C. for 2 hours under an air atmosphere, and fired at
500.degree. C. for 6 hours under an argon gas atmosphere. Then, the
resulting Na.sub.2MnPO.sub.4F was precipitated in acetonitrile
including 3 M of LiBr dissolved therein, and reacted together with
the flow of argon gas at a reaction temperature of 80.degree.
C.
[0064] The test sample, in which ion exchange was completed, was
washed with anhydrous ethanol so as to remove the remaining NaBr,
and subsequently dried. Then, the resulting test sample was
uniformly mixed with Super-P in a ratio of 75:25 by ball-milling
and then, prepared as a cathode material composite.
Comparative Example 1
[0065] Sodium carbonate (Na.sub.2CO.sub.3), manganese
oxalate.hydrate (MnC.sub.2O.sub.4.2H.sub.2O), sodium fluoride
(NaF), sodium hydrogen carbonate (NaHCO.sub.3), and ammonium
phosphate (NH.sub.4H.sub.2PO.sub.4) were introduced in
predetermined amounts with respect to the total amount of 5 g, and
uniformly mixed by hand mixing for 30 minutes.
[0066] The resulting mixture was subjected to pretreatment at
300.degree. C. for about 2 hours under an air atmosphere, and fired
at 500.degree. C. for 6 hours under an argon gas atmosphere. Then,
the resulting Na.sub.2MnPO.sub.4F was precipitated in acetonitrile
including 3 M of LiBr dissolved therein, and reacted together with
the flow of argon gas at A reaction temperature of 80.degree. C.
After the completion of the reaction, the resulting test sample was
collected, washed with anhydrous ethanol, and subsequently dried,
so as to remove the remaining impurities. Then, only a pure test
sample was collected.
Comparative Example 2
[0067] Sodium carbonate (Na.sub.2CO.sub.3), manganese
oxalate.hydrate (MnC.sub.2O.sub.4.2H.sub.2O), sodium fluoride
(NaF), sodium hydrogen carbonate (NaHCO.sub.3), and ammonium
phosphate (NH.sub.4H.sub.2PO.sub.4) were introduced in
predetermined amounts with respect to the total amount of 10 g, and
uniformly mixed by ball milling for 6 hours.
[0068] The resulting mixture was subjected to pretreatment at
300.degree. C. for 2 hours under an air atmosphere, and fired at
600.degree. C. for 6 hours under an argon gas atmosphere. Then, the
resulting Na.sub.2MnPO.sub.4F was precipitated in acetonitrile
including 3 M of LiBr dissolved therein, and reacted together with
the flow of argon gas at a reaction temperature of 80.degree. C.
After the completion of the reaction, the resulting test sample was
collected, washed with anhydrous ethanol, and subsequently dried,
so as to remove the remaining impurities. Then, only a pure test
sample was collected.
Comparative Example 3
[0069] Sodium carbonate (Na.sub.2CO.sub.3), manganese
oxalate.hydrate (MnC.sub.2O.sub.4.2H.sub.2O), sodium fluoride
(NaF), sodium hydrogen carbonate (NaHCO.sub.3), and ammonium
phosphate (NH.sub.4H.sub.2PO.sub.4) were introduced in
predetermined amounts with respect to the total amount of 10 g, and
uniformly mixed by ball milling for 6 hours.
[0070] The resulting mixture was subjected to pretreatment at
300.degree. C. for 2 hours under an air atmosphere, and fired at
600.degree. C. for 3 hours under an argon gas atmosphere. Then, the
resulting Na.sub.2MnPO.sub.4F was precipitated in acetonitrile
including 3 M of LiBr dissolved therein, and reacted together with
the flow of argon gas at a reaction temperature of 80.degree. C.
After the completion of the reaction, the resultant test sample was
collected, washed with anhydrous ethanol, and subsequently dried so
as to remove the remaining impurities. Then, only a pure test
sample was collected.
Comparative Example 4
[0071] Sodium carbonate (Na.sub.2CO.sub.3), manganese
oxalate.hydrate (MnC.sub.2O.sub.4.2H.sub.2O), sodium fluoride
(NaF), sodium hydrogen carbonate (NaHCO.sub.3), and ammonium
phosphate (NH.sub.4H.sub.2PO.sub.4) were introduced in
predetermined amounts with respect to the total amount of 10 g, and
uniformly mixed by ball milling for 6 hours.
[0072] The resulting mixture was subjected to pretreatment at
300.degree. C. for 2 hours under an air atmosphere, and fired at
550.degree. C. for 6 hours under an argon gas atmosphere. Then, the
resulting Na.sub.2MnPO.sub.4F was precipitated in acetonitrile
including 3 M of LiBr dissolved therein, and reacted together with
the flow of argon gas at a reaction temperature of 80.degree. C.
After the completion of the reaction, the resulting test sample was
collected, washed with anhydrous ethanol, and subsequently dried so
as to remove the remaining impurities. Then, only a pure test
sample was collected.
Comparative Example 5
[0073] Sodium carbonate (Na.sub.2CO.sub.3), manganese
oxalate.hydrate (MnC.sub.2O.sub.4.2H.sub.2O), sodium fluoride
(NaF), sodium hydrogen carbonate (NaHCO.sub.3), and ammonium
phosphate (NH.sub.4H.sub.2PO.sub.4) were introduced in
predetermined amounts with respect to the total amount of 10 g, and
uniformly mixed by ball milling for 6 hours.
[0074] The resulting mixture was subjected to pretreatment at
300.degree. C. for 2 hours under an air atmosphere, and fired at
550.degree. C. for 3 hours under an argon gas atmosphere. Then, the
resulting Na.sub.2MnPO.sub.4F was precipitated in acetonitrile
including 3 M of LiBr dissolved therein, and reacted together with
the flow of argon gas at a reaction temperature of 80.degree. C.
After the completion of the reaction, the resulting test sample was
collected, washed with anhydrous ethanol, and subsequently dried so
as to remove the remaining impurities. Then, only a pure test
sample was collected.
Experimental Example 1
Test on Performance of an Electrode
[0075] The primary particle size of cathode materials prepared from
Experimental Example 1, and Comparative Examples 1 and 2 was
measured, and metal composition within the cathode materials was
analyzed by ICP emission spectrochemical analysis. The results are
noted in Table 1.
TABLE-US-00001 TABLE 1 LiBr Primary Composition analysis result
(molar ratio) molarity particle size Li Na Mn PO.sub.4 Exp. 1 3.0M
300 nm 2.0 0 1.0 1.0 Comp. Exp. 1 3.0M 2 .mu.m 0 2.0 1.0 1.0 Comp.
Exp. 2 3.0M 1 .mu.m 0 2.0 1.0 1.0 Comp. Exp. 3 3.0M 800 nm 0.2 1.8
1.0 1.0 Comp. Exp. 4 3.0M 700 nm 0.35 1.65 1.0 1.0 Comp. Exp. 5
3.0M 500 nm 0.4 1.6 1.0 1.0
[0076] The cathode material from Example 1, which had a primary
particle size of 300 nm, was prepared into Li.sub.2MnPO.sub.4F by
ion exchange between lithium and sodium. It was found that ion
exchange did not occur in cathode materials having a primary
particle size of 1 .mu.m or more (i.e., from Comparative Examples 1
to 3). In cathode materials having a primary particle size of 500
nm to 800 nm (i.e., from Comparative Examples 3 to 5), it was found
that when ion exchange was carried out using the same lithium
source (i.e., 3 M LiBr), only a small amount of lithium was reacted
and exchanged.
[0077] Accordingly, it was found that in order to intercalate
lithium into Na.sub.2MnPO.sub.4F through a chemical method, such as
ion exchange, it is important to control the particle size.
According to the invention, the particle size was controlled by
carrying out by controlling the ball milling and heat treatment
conditions; however, one of ordinary skill in the art will
understand that these conditions may vary according to the types of
devices and procedures used for the aforementioned methods. The
important aspect is that the ability to obtain Li.sub.2MnPO.sub.4F
through complete substitution of two lithiums is efficient only
when the primary particle size is controlled to a predetermined
size or less.
[0078] By using powder of the cathode material composite from
Example 1, 95 wt % of cathode material composite was mixed with 5
wt % of binding agent PVdF, and then a slurry was prepared by using
N-methyl pyrrolidone (NMP) as a solvent.
[0079] The slurry was applied to aluminum (Al) foil with a
thickness of 20 .mu.m, and then dried and consolidated by press.
The resulting product was dried under a vacuum at 120.degree. C.
for 16 hours, so as to provide a circular electrode with a diameter
of 16 mm
[0080] As a counter electrode, a lithium metal foil punched with a
diameter of 16 mm was used, and a polypropylene (PP) film was used
as a separator. Also, as an electrolyte, a solution containing 1 M
LiPF.sub.6 in ethylene carbonate (EC) and dimethoxy ethane (DME)
mixed in a ratio of 1:1 (v/v) was used. The electrolyte was
impregnated in the separator, and the separator was positioned
between the operating electrode and the counter electrode. Then,
the electrode performance of a battery was tested by using a case
(SUS) as an electrode test cell. The measurement results including
discharge capacity are noted in Table 2 below.
TABLE-US-00002 TABLE 2 Discharge capacity at room temperature
Discharge voltage (mAhg.sup.-1) (V) Example 1 120 2.0 222 1.0
[0081] As shown in FIG. 1A and FIG. 1B, when the surface of a test
sample was observed by an electron microscope before and after ion
exchange treatment, it was observed that the surface of the test
sample became rough after ion exchange due to deintercalation of
sodium and intercalation of lithium.
[0082] The results of the test of electrochemical characteristics
revealed a capacity of 120 mAhg.sup.-1 at a discharge cut-off
voltage of 2.0 V, and a capacity of 222 mAhg.sup.-1 at a discharge
cut-off voltage of 1.0 V.
[0083] Charge/discharge curve graphs of a battery including the
cathode material from Example 1, at room temperature, are shown in
FIGS. 2 and 3. Also, as shown in FIG. 4, charge/discharge curve
graphs of a battery including the cathode material from Example 1,
at a high temperature (60.degree. C.), show that the potential
plateau is 3.9 V. Accordingly, the cathode material of the
invention, lithium manganese fluorophosphate Li.sub.2MnPO.sub.4F,
synthesized through an ion exchange method, can be subjected to
charge/discharge by electrochemical intercalation/deintercalation
of lithium; consequently, the cathode material displays a
sufficient discharge capacity.
[0084] The invention has been described in detail with reference to
exemplary thereof. However, it will be appreciated by those skilled
in the art that changes may be made in these embodiments without
departing from the principles and spirit of the invention, the
scope of which is defined in the appended claims and their
equivalents.
* * * * *