KR20120139448A - Positive-electrode active material and lithium secondary battery including them - Google Patents

Abstract

PURPOSE: A positive electrode active material which is processed to introduce cheap anode material and a lithium secondary battery including the same are provided to enhance lifetime property and safety. CONSTITUTION: A lithium secondary battery includes positive active material composed of composite dimensional manganese oxide represented by chemical formula 1 or. The chemical formula 1 and 2 are as follows: aMnO_2_(1-a)Li_2MnO_3. The lithium secondary battery is manufactured by charging at voltage of 4.9V or higher in a first formation process. Here, 0<a<1, 0<x<2.

Description

Positive electrode active material and a lithium secondary battery comprising the same {positive-electrode active material and Lithium secondary battery including them}

The present invention relates to a positive electrode active material and a lithium secondary battery including the same, and more particularly, to a positive electrode active material and a lithium secondary battery including the same, which are processed to introduce a cathode material having good capacity and lifetime characteristics and inexpensive good capacity. It is about.

Recently, lithium secondary batteries have been used in various fields including portable electronic devices such as mobile phones, PDAs, and laptop computers. In particular, as interest in environmental issues grows, lithium secondary batteries having high energy density and discharge voltage as driving sources of electric vehicles that can replace fossil fuels such as gasoline and diesel vehicles, which are one of the main causes of air pollution, are developed. Research on batteries is actively underway and some commercialization stages are in progress. Meanwhile, in order to use a lithium secondary battery as a driving source of such an electric vehicle, it must be able to maintain a stable output in a SOC section with high output.

As a cathode material of a high capacity lithium secondary battery, LiCoO ₂ , which is a typical cathode material, has reached an increase in energy density and a practical limit of output characteristics. In particular, when used in high energy density applications, it is charged due to its structural instability. In the state, along with structural modification, oxygen is released in the structure, causing exothermic reaction with the electrolyte in the battery, which is the main cause of battery explosion. In order to improve the safety problem of LiCoO ₂ , the use of lithium-containing manganese oxides such as LiMnO _{2 having} a layered crystal structure and LiMn ₂ O _{4 having a} spinel crystal structure and lithium-containing nickel oxide (LiNiO ₂ ) has been considered. Many studies have been conducted on the layered lithium manganese oxide in which Mn is added to the layered lithium manganese oxide as an essential transition metal in a larger amount than other transition metals (except lithium).

The lithium manganese oxide has a relatively large capacity and has a relatively high output characteristic in the high SOC region, but has a disadvantage in that the resistance rapidly increases in the operating voltage terminal, that is, in the low SOC region, and thus the output rapidly decreases. There is a problem that the irreversible capacity is large.

The present invention provides a lithium secondary battery having a high capacity and excellent lifespan characteristics and comprising a cathode active material which is cheaper than other cathode active material materials.

The present invention also provides a method of manufacturing the lithium secondary battery.

In order to solve the above problems, the present invention includes a cathode active material composed of manganese oxide (Composite Dimensional Manganese Oxide: hereinafter, CDMO) represented by the following [Formula 1] and charged at a voltage of 4.9 V or more in the first formation process It provides a lithium secondary battery characterized by the above-mentioned.

AMnO ₂ ? (1-a) Li ₂ MnO ₃ (0 <a <1)

A in Formula 1 is characterized in that 0.1 to 0.5,

It is preferable that the cathode active material further includes a conductive material.

The conductive material is preferably made of graphite and conductive carbon.

In addition, the conductive material is characterized in that it comprises 0.5 to 15 parts by weight based on 100 parts by weight of the positive electrode active material.

Specifically, the conductive carbon is one selected from the group consisting of carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black, or a material whose crystal structure includes graphene or graphite. Or more characterized in that the mixed material.

In addition, the lithium secondary battery is lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium cobalt-nickel oxide, lithium cobalt-manganese oxide, lithium manganese-nickel oxide, lithium cobalt- in addition to the manganese oxide represented by [Formula 1] Nickel-manganese oxide and at least one lithium-containing metal oxide selected from the group consisting of an oxide substituted or doped with them is characterized in that it further comprises.

In this case, the ellipsoid is selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti and Bi It is characterized by being at least one species.

The lithium-containing metal oxide is characterized in that contained within 50 parts by weight based on 100 parts by weight of the positive electrode active material.

The present invention also provides a lithium secondary battery comprising a cathode active material composed of a composite dimensional manganese oxide (hereinafter referred to as CDMO) represented by the following [Formula 2].

A Li _x MnO ₂ ? (1-a) Li _(2-x) MnO ₃ (0 <a <1, 0 <x <2)

A in Formula 2 is characterized in that 0.1 to 0.5.

The positive electrode active material is characterized in that it further comprises a conductive material, and the conductive material is characterized in that consisting of graphite and conductive carbon, the conductive material is contained in 0.5 to 15 parts by weight based on 100 parts by weight of the positive electrode active material It features.

The conductive carbon is one selected from the group consisting of carbon black, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black, or a material whose crystal structure includes graphene or graphite. The above is characterized by being a mixed material.

The lithium secondary battery may be lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium cobalt-nickel oxide, lithium cobalt-manganese oxide, lithium manganese-nickel oxide, lithium cobalt-nickel- in addition to manganese oxide represented by [Formula 1] At least one lithium-containing metal oxide selected from the group consisting of manganese oxides and oxides in which ellipsoid (s) are substituted or doped thereto is further included.

The ellipsoid is selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti, and Bi. It is characterized by more than one species.

The lithium-containing metal oxide is characterized in that contained within 50 parts by weight based on 100 parts by weight of the positive electrode active material.

The present invention further provides a battery module or a battery pack, comprising two or more lithium secondary batteries electrically connected to each other.

Lithium secondary battery according to the present invention is not particularly limited in use, it can be applied to all the various fields that can be applied to the secondary battery is, of course. In particular, the battery module or battery pack includes a power tool; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (PHEV); Electric two-wheeled vehicles including E-bikes and E-scooters; Electric golf carts; Electric trucks; It can also be used as a power source for any one or more of the medium-to-large devices of electric commercial vehicles or power storage systems.

On the other hand, the present invention comprises the steps of preparing a lithium secondary battery comprising a positive electrode active material composed of manganese oxide (Composite Dimensional Manganese Oxide: hereinafter, CDMO) represented by the following [Formula 1];

It further provides a method of manufacturing a lithium secondary battery comprising a formation step of charging the lithium secondary battery at a voltage of 4.9 V or more.

AMnO ₂ ? (1-a) Li ₂ MnO ₃ (0 <a <1)

A in Formula 2 is characterized in that 0.1 to 0.5.

The present invention can provide a secondary battery including a cathode active material having a relatively low cost, stable and high capacity.

1 is a graph measuring the capacity according to the voltage at the time of the first charge of the lithium secondary battery according to the Examples and Comparative Examples of the present invention.
2 is a graph evaluating the discharge capacity according to the number of cycles of a lithium secondary battery according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail.

The present invention is to solve the above problems,

Lithium secondary battery comprising a cathode active material composed of a composite dimensional manganese oxide (hereinafter referred to as CDMO) represented by the following [Formula 1], characterized in that the lithium battery produced by charging at a voltage of 4.9 V or more in the first formation process It provides a secondary battery.

AMnO ₂ ? (1-a) Li ₂ MnO ₃ (0 <a <1)

CDMO of Formula 1 is obtained by replacing a part of the MnO ₂ material with lithium (Li), the crystal structure is a complex structure containing Li ₂ MnO ₃ and γ / β-MnO ₂ . Pure case of using a material consisting of only MnO ₂ as a positive electrode active material, the longer charge-discharge proceeds crystal structure is collapsed further bar which can not serve as a positive electrode active material, that is defective in the life characteristics of the positive electrode active material of only the pure MnO ₂ is In the case of aMnO ₂ ? (1-a) Li ₂ MnO ₃ obtained by replacing a part of MnO ₂ material with lithium (Li) as described above, Li ₂ MnO ₃ can maintain a crystal structure in the middle of the crystal structure. By acting as a pillar to maintain the crystal structure even if the charge and discharge continuously proceeds to improve the life characteristics of the pure MnO ₂ .

However, lithium included in Li ₂ MnO ₃ in the CDMO is not used in the charging and discharging process of the battery even after the formation process of the battery, and therefore requires an additional external lithium source. Accordingly, the CDMO is a positive electrode alone. It could not be applied as an active material and always had to be mixed or complexed with other lithium transition metal oxides and applied as a cathode active material.

When lithium is supplied, the CDMO has an operating voltage in the region of about 2.5 to 3.3V during charging and discharging, and has an initial theoretical capacity of 200 mAh / g. If applicable, there are many advantageous advantages.

Accordingly, the present applicant is to charge the lithium secondary battery at a voltage of 4.9 V or more in the first formation process in order to use a secondary battery including a cathode active material to which the CDMO is applied alone.

In the case of charging at a relatively high voltage level, lithium (Li) contained in Li ₂ MnO ₃ is released and activated. Afterwards, the activated lithium does not return to Li ₂ MnO ₃ in the discharge process. _It was found that the insertion into _two phases continued to participate in the charge / discharge process of the battery.

Therefore, when charging at a high voltage of 4.9V or higher only once in the initial charging process, it is possible to implement a high performance lithium secondary battery applied by CDMO alone.

When a total amount of the CDMO is 1 part by weight in aMnO ₂ ? (1-a) Li ₂ MnO ₃ (0 <a <1) of Formula 1, Li ₂ MnO ₃ is preferably included in less than 0.5 part by weight. More preferably 0.1 to 0.5 parts by weight. The Li ₂ MnO ₃ is to supply lithium on the MnO ₂ is activated because it can sufficiently supply the lithium necessary for charging and discharging behavior within the above range.

The secondary battery including the cathode active material composed of the CDMO of Formula 1 is charged at a voltage of 4.9V or more in the first formation process.

The lithium in the CDMO is activated by the formation and then participates in the charge / discharge process. Thus, the secondary battery according to the present invention includes a cathode active material of lithium manganese oxide represented by Formula 2 below.

[Formula 2] a Li _x MnO ₂ (1-a) Li _(2-x) MnO ₃ (0 <a <1, 0 <x <2)

Since the secondary battery including the cathode active material according to the present invention exhibits a relatively high capacity and excellent life characteristics, it can be applied to all the various fields requiring a secondary battery.

On the other hand, in the present invention, the manufacturing method of the CDMO is not particularly limited and may be prepared using a known method. In addition, the method of forming the cathode active material using the CDMO is not particularly limited, and various methods known in the art may be adopted.

The positive electrode active material according to the present invention may further include a conductive material, and preferably may include two or more conductive materials having different particle sizes or shapes. The method of including the conductive material is not particularly limited, and conventional methods known in the art, such as coating on the positive electrode active material, can be adopted.

As described above, the conductivity may be increased by including conductive materials having different sizes or shapes. In a preferred embodiment of the present invention, graphite and conductive carbon may be used simultaneously as the conductive material.

In this way, the conductive material may be further included to further improve conductivity and output, and at the same time, a high capacity cathode material having a wide available SOC section may be provided.

Further, the positive electrode active material may be lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium cobalt-nickel oxide, lithium cobalt-manganese oxide, lithium manganese-nickel oxide, lithium cobalt-nickel-manganese oxide and ellipsoid (s) thereof. ) May further include one or more lithium-containing metal oxides selected from the group consisting of substituted or doped oxides. The ellipsoid may be Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, It may be one or more selected from the group consisting of Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti and Bi.

In this case, the lithium-containing metal oxide may be included within 50 parts by weight based on 100 parts by weight of the positive electrode active material.

In addition, the conductive material may be graphite or conductive carbon, and the like, and the conductive material is not particularly limited as long as it has excellent electrical conductivity and has conductivity without causing side reactions in the internal environment of the lithium secondary battery or causing chemical change in the battery.

Specifically, the graphite is not limited to natural graphite or artificial graphite, and the conductive carbon is preferably a highly conductive carbon-based material, specifically, carbon black, acetylene black, Ketjen black, channel black, furnace black, Carbon black, such as lamp black, summer black, or a mixture of one or more selected from the group consisting of a material having a crystal structure including graphene or graphite may be used. In some cases, a conductive polymer having high conductivity is also possible.

Here, the conductive material made of graphite and conductive carbon is preferably included in 0.5 to 15 parts by weight based on 100 parts by weight of the positive electrode active material. If the content of the conductive material is too small, less than 0.5 parts by weight, it is difficult to expect the effects described above. If the content of the conductive material is more than 15 parts by weight, it is difficult to increase the high capacity or high energy density because the amount of the positive electrode active material is relatively small. Can be.

In this case, the content of the conductive carbon may be included in an amount of 1 to 13 parts by weight, preferably 3 to 10 parts by weight, based on 100 parts by weight of the positive electrode active material.

The present invention provides a lithium secondary battery including the cathode active material.

In general, a lithium secondary battery includes a positive electrode composed of a positive electrode material and a current collector, a negative electrode composed of a negative electrode material and a current collector, and a separator capable of blocking electron conduction and conducting lithium ions between the positive electrode and the negative electrode. The void of the separator material contains an electrolyte for conducting lithium ions.

The positive electrode and the negative electrode are usually prepared by applying a mixture of an electrode active material, a conductive agent and a binder on a current collector and then drying, and a filler may be further added to the mixture as necessary.

The lithium secondary battery of the present invention can be manufactured according to a conventional method in the art. Specifically, it can be prepared by putting a porous separator between the positive electrode and the negative electrode, the non-aqueous electrolyte.

The present invention further provides a battery module or a battery pack, comprising two or more lithium secondary batteries electrically connected to each other.

The lithium secondary battery according to the present invention is not particularly limited in its use and may be applied to all the various fields in which the secondary battery may be applied. In particular, the battery module or battery pack includes a power tool; Electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); Electric two-wheeled vehicles including E-bikes and E-scooters; Electric golf carts; Electric trucks; It can also be used as a power source for any one or more of the medium-to-large devices of electric commercial vehicles or power storage systems.

Hereinafter, the content of the present invention through the specific examples will be described in more detail.

Example

Manufacture of anode

As the cathode active material, 0.9MnO ₂ ? 0.1Li ₂ MnO ₃ A slurry was prepared by adding 90 wt%, 6 wt% of denca black as a conductive material, and 4 wt% of PVDF as a binder to NMP. This was coated on aluminum (Al) foil, which is a positive electrode current collector, and rolled and dried to prepare a positive electrode for a lithium secondary battery.

Of lithium secondary battery  Produce

A polymer electrolyte was manufactured by injecting a lithium electrolyte solution through a separator of porous polyethylene between the cathode prepared as described above and the graphite cathode.

The polymer type lithium secondary battery was charged and formed at 4.9 V, and then the life characteristics were measured while charging and discharging between 4.2 V and 2.5 V. (C-rate = 1C).

Comparative example

A secondary battery was manufactured in the same manner as in the above example, and the output was measured in the same manner except that no formation was performed.

Experimental Example

1 to 2 by measuring the capacity and life cycle characteristics of the battery in a voltage range of 4.2V to 2.5V for a full cell lithium secondary battery prepared by the above Examples and Comparative Examples described in Figures 1 to 2 It was.

As shown in Figure 1, when not formed at a high voltage, the charging capacity of the battery is not expressed at all, the secondary battery according to an embodiment of the present invention expressed a high capacity of 250mAh / g or more at the first charge, Since the characteristics of the high capacity were all expressed in the post discharge process, it was confirmed that the high capacity high life secondary battery using the CDMO could be implemented according to the present invention.

In addition, as shown in FIG. 2, the secondary battery according to the present invention maintains a constant and even discharge capacity even after continuously charging and discharging at a general level of voltage after forming at a high voltage only at the first charge. It was confirmed to be excellent and high in safety.

As a result, it was confirmed that the lithium secondary battery according to the present invention can provide a lithium secondary battery having excellent life characteristics at high capacity and improved safety at low cost.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. The scope of the present invention should be interpreted based on the scope of the following claims and all technical ideas within the scope of equivalents thereof are to be construed as being included in the scope of the present invention. It is to be understood that the invention is not limited thereto.

Claims (22)

A lithium secondary battery comprising a cathode active material composed of manganese oxide (Composite Dimensional Manganese Oxide: hereinafter, CDMO) represented by the following [Formula 1] and was charged at a voltage of 4.9 V or more in the first formation process.
AMnO ₂ ? (1-a) Li ₂ MnO ₃ (0 <a <1)
The method of claim 1,
In Formula 1, a is a lithium secondary battery, characterized in that 0.1 to 0.5.
The method of claim 1,
The cathode active material further comprises a conductive material. The method of claim 3, wherein
The conductive material is a lithium secondary battery, characterized in that made of graphite and conductive carbon. The method of claim 3, wherein
The conductive material is a lithium secondary battery, characterized in that contained in 0.5 to 15 parts by weight based on 100 parts by weight of the positive electrode active material.
The method of claim 4, wherein
The conductive carbon is one selected from the group consisting of carbon black, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black, or a material whose crystal structure includes graphene or graphite. Lithium secondary battery characterized in that the above mixture.
The method of claim 1,
The lithium secondary battery has a lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium cobalt-nickel oxide, lithium cobalt-manganese oxide, lithium manganese-nickel oxide, lithium cobalt-nickel- in addition to the manganese oxide represented by [Formula 1] A lithium secondary battery further comprising at least one lithium-containing metal oxide selected from the group consisting of manganese oxides and oxides substituted or doped with ellipsoid (s).
The method of claim 7, wherein
The ellipsoid is selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti, and Bi. Lithium secondary battery characterized by the above-mentioned.
The method of claim 7, wherein
The lithium-containing metal oxide is lithium secondary battery, characterized in that contained within 50 parts by weight based on 100 parts by weight of the positive electrode active material.
A lithium secondary battery comprising a cathode active material composed of manganese oxide represented by the following [Formula 2] (Composite Dimensional Manganese Oxide: CDMO).
ALi _x MnO ₂ ? (1-a) Li _(2-x) MnO ₃ (0 <a <1, 0 <x <2)
11. The method of claim 10,
A in Formula 2 is 0.1 to 0.5, wherein the lithium secondary battery. 11. The method of claim 10,
The cathode active material further comprises a conductive material.
13. The method of claim 12,
The conductive material is a lithium secondary battery, characterized in that made of graphite and conductive carbon.
13. The method of claim 12,
The conductive material is a lithium secondary battery, characterized in that contained in 0.5 to 15 parts by weight based on 100 parts by weight of the positive electrode active material.
The method of claim 13,
The conductive carbon is one selected from the group consisting of carbon black, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black, or a material whose crystal structure includes graphene or graphite. Lithium secondary battery characterized in that the above mixture.
The method of claim 10,
The lithium secondary battery has a lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium cobalt-nickel oxide, lithium cobalt-manganese oxide, lithium manganese-nickel oxide, lithium cobalt-nickel- in addition to the manganese oxide represented by [Formula 1] A lithium secondary battery further comprising at least one lithium-containing metal oxide selected from the group consisting of manganese oxides and oxides substituted or doped with ellipsoid (s).
17. The method of claim 16,
The ellipsoid is selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti, and Bi. Lithium secondary battery characterized by the above-mentioned.
17. The method of claim 16,
The lithium-containing metal oxide is lithium secondary battery, characterized in that contained within 50 parts by weight based on 100 parts by weight of the positive electrode active material. 19. A medium-large battery module or battery pack comprising two or more lithium secondary batteries according to any one of claims 1 to 18 electrically connected thereto.
The method of claim 19,
The medium-large battery module or battery pack includes a power tool; Electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); Electric two-wheeled vehicles including E-bikes and E-scooters; Electric golf carts; Electric trucks; Medium-large battery module or battery pack, characterized in that used as a power source for any one or more of the medium-to-large device of a commercial vehicle or power storage system.
Preparing a lithium secondary battery including a cathode active material including a composite dimensional manganese oxide (hereinafter, referred to as CDMO) represented by Formula 1;
A method of manufacturing a lithium secondary battery comprising the step of charging the lithium secondary battery at a voltage of 4.9 V or more.
AMnO ₂ ? (1-a) Li ₂ MnO ₃ (0 <a <1)
22. The method of claim 21,
A in Formula 2 is 0.1 to 0.5, wherein the lithium secondary battery.

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