KR102280548B1 - cathode for lithium secondary battery comprising double layer cathode active material - Google Patents

Abstract

The present invention relates to a positive electrode active material formed of a double layer and a positive electrode for a lithium secondary battery comprising the same, Li(Ni _x Co _y Mn _z )O ₂ (0<x<1, 0<y<1, 0<z<1 , x+y+z=1) layer and Li(Ni _x Co _y Mn _z )O _{2 By including the LiCoO 2} layer formed on the upper surface, an electrode having a high capacity and a long life can be provided.

Description

A cathode electrode for a lithium secondary battery comprising a double layer cathode active material

The present invention relates to a positive electrode active material formed in a double layer to realize high capacity and long life, and a positive electrode for a lithium secondary battery including the same.

With the rapid development of communication and computer industries, camcorders, mobile phones, notebook PCs, and the like are undergoing remarkable development, and the demand for lithium secondary batteries as a power source for driving these portable electronic communication devices is increasing day by day. In particular, as an eco-friendly power source, R&D is being actively conducted in Japan, Europe, and the United States as well as in Korea in relation to the application of electric vehicles, uninterruptible power supplies, power tools, and satellites.

Moreover, as the commercialization of lithium secondary batteries has recently been expanded, the problems of increasing the capacity and safety of lithium secondary batteries are further emerging.

_{On the other hand, lithium cobalt oxide (LiCoO 2} ) has been mainly used as a positive electrode active material for lithium secondary batteries, but lithium nickel oxide (Li(Ni-Co-Al)O ₂ ) and lithium composite metal oxide are currently used as other layered positive electrode active materials. (Li(Ni-Co-Mn)O ₂ ) and the like are also used, and in addition, low-cost, high-stability spinel-type lithium manganese oxide (LiMn ₂ O ₄ ) and olivine-type lithium iron phosphate compound (LiFePO ₄ ) are also attracting attention.

The lithium secondary battery using the lithium cobalt oxide, lithium nickel oxide, lithium composite metal oxide, etc. has excellent basic battery characteristics, but safety, particularly thermal stability, overcharging characteristics, etc. are not sufficient. When the fillability of the active material is increased, there is a problem in that safety is further reduced.

In addition, spinel-type lithium manganese-based batteries have advantages of low price and high safety, and are currently being actively studied as a cathode active material for lithium secondary batteries used as power sources for electric vehicles. There is a problem in that it does not meet the needs.

In addition, although the olivine-type lithium iron phosphate compound has low price and high safety characteristics, it is difficult to expect excellent battery characteristics due to its very low electronic conductivity, and the average operating potential is low, which does not satisfy the demand for high capacity.

Accordingly, various studies have been conducted to solve the above problems, but an effective solution other than a layered positive electrode active material has not been presented until now.

Republic of Korea Patent Publication No. 2016-0083638 Republic of Korea Patent No. 1520146

An object of the present invention is to provide a positive electrode active material formed as a double layer to realize high capacity and long life.

Another object of the present invention is to provide a positive electrode for a lithium secondary battery including the positive active material.

In addition, another object of the present invention is to provide a lithium secondary battery including the positive electrode.

In addition, another object of the present invention is to provide a lithium capacitor including the positive electrode.

Another object of the present invention is to provide a device including the anode electrode.

The double-layer cathode active material of the present invention for achieving the above object is Li(Ni _x Co _y Mn _z )O ₂ (0<x<1, 0<y<1, 0<z<1, x+y+z= 1) layer and a LiCoO ₂ layer _{formed on the Li(Ni x} Co _y Mn _z )O _{2 layer.}

The Li (Ni _x Co _y Mn _z) O thickness of the _second layer is 20 to 40 ㎛, the LiCoO may be a thickness of the _second layer is 30 to 50 ㎛, the thickness of the LiCoO ₂ layer is Li (Ni _x Co _y It may be 5-10 μm thicker than the thickness of the _{Mn z} )O _{2 layer.}

The Li(Ni _x Co _y Mn _z )O ₂ and LiCoO ₂ may be used in a weight ratio of 60:40 to 80:20.

In the Li(Ni _x Co _y Mn _z )O ₂ , x may be a prime number of 0.6-0.8, y may be a prime number of 0.1-0.3, and z may be a prime number of 0.1-0.3.

In addition, the positive electrode for a lithium secondary battery of the present invention for achieving the above other object is a current collector (current collector), Li (Ni _x Co _y Mn _z ) O ₂ (0<x<1 formed on the upper surface of the current collector) , 0<y<1, 0<z<1, x+y+z=1) layer, and _{a LiCoO 2} layer formed on an upper surface of _{the Li(Ni x} Co _y Mn _z )O _{2 layer.}

The Li(Ni _x Co _y Mn _z )O ₂ layer may have a thickness of 20 to 40 μm, and the LiCoO ₂ layer may have a thickness of 30 to 50 μm.

The thickness of the LiCoO ₂ layer may be 5 to 10 μm thicker than the thickness of the Li(Ni _x Co _y Mn _z )O _{2 layer.}

The Li(Ni _x Co _y Mn _z )O ₂ and LiCoO ₂ may be used in a weight ratio of 60:40 to 80:20.

In addition, the lithium secondary battery of the present invention for achieving the above another object may include the positive electrode.

In addition, the lithium capacitor of the present invention for achieving the above another object may include the positive electrode.

In addition, the device of the present invention for achieving the above another object includes the positive electrode, the device may be selected from the group consisting of communication equipment, energy storage system (Energy Storage System, ESS) and transportation means. there is.

The positive electrode including the double-layer positive active material of the present invention can be used stably for a long time while having a high capacity.

In particular, the positive active material of the present invention can improve electrochemical properties such as stability in a high voltage region, electrode capacity and cycle life.

1 is a structural diagram showing the structure of a typical anode electrode.
2 is a structural diagram showing the structure of a positive electrode to which the double-layer positive active material of the present invention is applied.
Figure 3a is a photograph taken by SEM of the cross section of the anode electrode prepared according to the Example and Comparative Example of the present invention, Figure 3b is the cross section of the cathode electrode prepared according to the Example and Comparative Example through EDS mapping of the electrode This is a picture of the structure.
Figure 4a is a graph measuring the discharge capacity after 1C charging and discharging of the battery to which the positive electrode prepared according to the Examples and Comparative Examples of the present invention is applied, and Figure 4B is the battery to which the positive electrode prepared according to the Examples and Comparative Examples is applied. It is a graph measuring the discharge capacity after charging and discharging at 2C.
5A is a picture taken by SEM of the cross-section (electrolyte side) of the electrode after 140 cycles at 1C of a battery to which the positive electrode prepared according to Example 1 of the present invention is applied, and FIG. 5B is a positive electrode manufactured according to Comparative Example 1 The cross-section of the electrode (current collector side) after 140 cycles at 1C of the battery to which the electrode is applied is a photograph taken by SEM, and FIG. 5C is the cross-section of the electrode after 140 cycles at 1C of the battery to which the positive electrode prepared according to Comparative Example 2 is applied. (electrolyte side) is a photograph taken by SEM, and FIG. 5d is a photograph taken by SEM of the cross-section (collector side) of the electrode after 140 cycles at 1C of the battery to which the positive electrode prepared according to Comparative Example 2 is applied.
6A is a photograph taken by SEM of the cross-section (electrolyte side) of the electrode after 90 cycles at 2C of a battery to which the positive electrode prepared according to Example 1 of the present invention is applied, and FIG. 6B is a positive electrode manufactured according to Comparative Example 1. The cross-section of the electrode (the current collector side) after 90 cycles at 2C of the battery to which the electrode is applied is a photograph taken by SEM, and FIG. 6c is the cross-section of the electrode after 90 cycles at 2C of the battery to which the positive electrode prepared according to Comparative Example 2 is applied. (electrolyte side) is a photograph taken by SEM, and FIG. 6d is a photograph taken by SEM of the cross-section (collector side) of the electrode after 90 cycles at 2C of the battery to which the positive electrode prepared according to Comparative Example 2 is applied.
7 is a graph of measuring the discharge capacity after charging and discharging according to the current of the battery to which the positive electrode manufactured according to the Examples and Comparative Examples of the present invention is applied.
8A is a graph measuring the voltage and discharge capacity for each current of the battery to which the positive electrode prepared according to Example 1 of the present invention is applied, and FIG. 8B is the voltage for each current of the battery to which the positive electrode prepared according to Comparative Example 1 is applied. and a graph measuring the discharge capacity, FIG. 8c is a graph measuring the voltage and discharge capacity for each current of the battery to which the positive electrode prepared according to Comparative Example 2 is applied, and FIG. 8D is the positive electrode prepared according to Comparative Example 3 It is a graph measuring the voltage and discharge capacity for each current of the applied battery.

The present invention relates to a positive electrode active material formed in a double layer to realize high capacity and long life, and a positive electrode for a lithium secondary battery including the same.

Since the positive electrode battery of a lithium secondary battery increases the amount of positive electrode active material in the electrode for high energy density, the thickness of the positive electrode becomes thicker and the stability is deteriorated. In general, the positive active material does not deteriorate equally during charging and discharging, but the positive active material particles located on the opposite side of the current collector rapidly deteriorate (the blue circle in FIG. 1 ), resulting in reduced efficiency.

In the _{past, LiCoO 2} (LCO) was mostly used as a positive electrode active material, but for realizing a high-capacity battery, a Li(Ni _x Co _y Mn _z )O ₂ (NCM) material using Ni instead of the Co transition metal has been developed. Since the Li(Ni _x Co _y Mn _z )O ₂ (NCM) material has a problem of having a low lifespan instead of having a high capacity, a high-capacity NCM material is coated on the bottom of the current collector to realize a long-life electrode while obtaining optimal energy After that, a positive electrode active material having a double layer in which a high safety LCO is laminated on the upper surface of the NCM material is introduced to realize a high capacity/high lifespan positive electrode.

Hereinafter, the present invention will be described in detail.

The cathode active material of the present invention has a structure formed in a double layer, specifically Li(Ni _x Co _y Mn _z )O ₂ (0<x<1, 0<y<1, 0<z<1, x+y+z= 1) (hereinafter referred to as NCM) layer and a LiCoO ₂ (hereinafter, LCO) layer _{formed on the Li(Ni x} Co _y Mn _z )O _{2 layer.}

The positive active material of the present invention is the NCM the thickness of the layer is from 20 to 40 μm, preferably from 20 to 30 μm; Although the thickness of the LCO layer is 30 to 50 μm, preferably 30 to 40 μm, it is laminated to a low thickness (a height of 50 to 90 μm) compared to a conventional positive active material that is usually laminated to a thickness of about 100 μm. It shows high energy density compared to the conventional electrode.

In particular, the thickness of the LCO layer is It is 5 to 10 μm thicker than the thickness of the layer, and the structure deterioration of the top layer is the most severe, but cracks do not occur in the upper LCO cathode active material after several cycles of charging and discharging, thereby exhibiting the effects of high capacity and long life.

In addition, the NCM particles and LCO particles of the present invention are used in a weight ratio of 60:40 to 80:20, preferably 60:40 to 70:30 by weight. If the NCM particles and the LCO particles are out of the above weight ratio, fine pinholes are generated in the positive electrode active material after several cycles of charging and discharging, so that the effect of high capacity and long life cannot be exhibited.

_{The particle diameter of Li(Ni x} Co _y Mn _z )O ₂ particles constituting the NCM layer is 1 to 10 μm, preferably 2 to 6 μm; _{The particle diameter of LiCoO 2} particles constituting the LCO layer is also 1 to 10 μm, preferably 2 to 6 μm. When the particle diameter of the two particles is less than the lower limit, the performance of the anode electrode may be deteriorated due to the small amount of conductive particles used in the cathode electrode, and when the particle diameter exceeds the upper limit, the lifespan may be reduced.

In the NCM particles used in the present invention, x may be a prime number of 0.6-0.8, y may be a prime number of 0.1-0.3, and z may be a prime number of 0.1-0.3. If the number of x, y, and z of the NCM particles is out of the above range, cracks may occur after several cycles of charging and discharging, thereby reducing the capacity and lifespan of the positive electrode.

In addition, the present invention provides a positive electrode for a lithium secondary battery comprising the double-layer positive electrode active material.

The positive electrode for a lithium secondary battery of the present invention includes a current collector, an NCM layer formed on an upper surface of the current collector, and the NCM and an LCO layer formed on top of the layer.

In the present invention, the effect of high capacity and long life can be obtained by stacking the current collector, the NCM layer and the LCO layer in this order. If an electrode stacked in the order of the current collector, the LCO layer and the NCM layer is used, the present invention Performance may be degraded compared to that, and when the LCO layer is used alone, high stability is shown, but the capacity is low, and when the NCM layer is used alone, there is a problem that the capacity is high but stability is low.

In addition, the present invention may provide a lithium secondary battery or lithium capacitor including the positive electrode for the lithium secondary battery.

Hereinafter, preferred examples are presented to aid the understanding of the present invention, but the following examples are merely illustrative of the present invention and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention, It goes without saying that such variations and modifications fall within the scope of the appended claims.

Example 1. Stacked in order of current collector, NCM layer, and LCO layer

_{LiNi 0 .8 Co 0 .1 Mn 0} .1 O 2 powder (NCM811) and the super-P (TIMCAL), PVdF (Polyvinylidene-fluoride) of a binder 94: 3 were mixed in a weight ratio of 3 by weight of the mixture A slurry was prepared by adding and mixing N-methylpyrrolidone (NMP). After casting the obtained slurry on Al foil (current collector) to a thickness of 40 μm using a bar coater, completely dry NMP in a convection oven at 120° C. and roll press LiNi _{0.8 so that the thickness becomes 30 μm.} A Co _0.1 Mn _0.1 O ₂ layer was formed.

LiCoO ₂ powder and super-P, PVdF binder was mixed in a weight ratio of 94:3:3, and then NMP (N-methylpyrrolidone) was added as much as the mass of the mixture and mixed to prepare a slurry. On the coated LiNi _0.8 Co _0.1 Mn _0.1 O ₂ layer, the prepared LiCoO ₂ slurry was cast to a thickness of 50 μm using a bar coater, and the NMP was completely dried in a convection oven at 120° C. _{A LiCoO 2} layer was formed so as to have a thickness of 40 μm to prepare a positive electrode stacked in this order of a current collector, a LiNi _0.8 Co _0.1 Mn _0.1 O ₂ layer, and a LiCoO _{2 layer.}

The structure of the prepared positive electrode was confirmed to be LiNi _0.8 Co _0.1 Mn _0.1 O ₂ and LiCoO ₂ 67:33 weight ratio according to the obtained ICP ratio.

Comparative Example 1. A current collector, an LCO layer, and an NCM layer are stacked in this order

The same procedure as in Example 1, except that the current collector, LiNi _0.8 Co _0.1 Mn _0.1 O ₂ layer, and LiCoO ₂ layer were laminated instead of the current collector, LiCoO ₂ layer, LiNi _0.8 Co _0.1 Mn _0.1 O ₂ layer was stacked in this order A positive electrode was prepared.

Comparative Example 2. NCM layer alone

LiNi _0.8 Co _0.1 Mn _0.1 O ₂ powder and super-P, PVdF (Polyvinylidene-fluoride) binder were mixed in a weight ratio of 94:3:3, and then NMP (N-methylpyrrolidone) was added as much as the mass of the mixture and mixed to make a slurry. (slurry) was prepared. After casting the obtained slurry on Al foil (current collector) to a thickness of 50 μm using a bar coater, dry NMP completely in a convection oven at 120° C. and roll press LiNi _{0.8 so that the thickness becomes 40 μm.} Co _0.1 Mn _0.1 O ₂ to form a layer of the positive electrode current collector in the electrode stack, LiNi _0.8 Co _0.1 Mn _0.1 O order of _two layers was prepared.

Comparative Example 3. LCO layer alone

LiCoO ₂ powder and super-P, PVdF binder was mixed in a weight ratio of 94:3:3, and then NMP (N-methylpyrrolidone) was added as much as the mass of the mixture and mixed to prepare a slurry. On the coated LiNi _0.8 Co _0.1 Mn _0.1 O ₂ layer, the prepared LiCoO ₂ slurry was cast to a thickness of 50 μm using a bar coater, and the NMP was completely dried in a convection oven at 120° C. _{A LiCoO 2} layer was formed to have a thickness of 40 μm to prepare a positive electrode in which a current collector and a LiCoO ₂ layer were stacked in this order.

Comparative Example 4. LiNi _0.8 Co _0.1 Mn _0.1 O ₂ + LiCoO ₂ Mixed layer (single layer structure)

LiNi _0.8 Co _0.1 Mn _0.1 O ₂ powder and LiCoO ₂ powder were mixed in a weight ratio of 67:33, and then the mixed metal oxide and super-P, PVdF binder were mixed in a weight ratio of 94:3:3. A slurry was prepared by adding and mixing NMP (N-methylpyrrolidone) by mass. After casting the obtained slurry on Al foil (current collector) to a thickness of 90 μm using a bar coater, completely dry NMP in a convection oven at 120° C. and roll press LiNi _{0.8 so that the thickness becomes 70 μm. Co 0.1 Mn 0.1 O 2 + LiCoO} 2 mixed layer of the positive electrode current collector laminated _{with, LiNi 0.8 Co 0.1 Mn 0.1 O} 2 + LiCoO ₂ in order to form a mixed layer was prepared.

<Test Example>

By punching the positive electrode prepared in the Examples and Comparative Examples with a disk having a diameter of 1.1 cm, a 2032 coin cell was prepared together with a Li disk, a PP separator, and 1.0 M LiPF6 EC/EMC (3:7 volume %) to produce electrochemical Evaluation was carried out.

Test Example 1. SEM measurement

Figure 3a is a photograph taken by SEM of the cross-section of the anode electrode prepared according to Examples and Comparative Examples, and Figure 3b is a cross-section of the anode electrode prepared according to Examples and Comparative Examples to measure the structure of the electrode through EDS mapping it's one picture

As shown in FIG. 3a , the LiNi _0.8 Co _0.1 Mn _0.1 O ₂ layer of Comparative Example 2 showed a large and small round structure, and the LiCoO ₂ layer of Comparative Example 3 had large and small geometric structures. . Accordingly, it was confirmed that Example 1 formed of a current collector/LiNi _0.8 Co _0.1 Mn _0.1 O ₂ layer/LiCoO ₂ layer had a large and small round structure on the lower side (current collector side) and a large and small geometrical structure on the upper side. did; It was confirmed that Comparative Example 1 formed of a current collector/LiCoO ₂ layer/LiNi _0.8 Co _0.1 Mn _0.1 O ₂ layer had a large and small geometrical structure on the lower side and a large and small round structure on the upper side; Full house comparison / LiCoO _2, LiNi _{0 .8} Co + Mn _{0 .1 0 .1} O formed in a _two-layer Example 4, it was confirmed that the mixed large and small geometric shape and type of spherical structure.

In addition, as shown in Figure 3b, in the electrode of Example 1, cobalt is more distributed on the upper side and nickel is distributed on the lower side, and Comparative Example 1 shows that, in contrast to Example 1, cobalt is more distributed on the lower side and nickel is further distributed on the upper side Confirmed.

Test Example 2. Measurement of Lifespan of Positive Electrode

Figure 4a is a graph measuring the discharge capacity after 1C charging and discharging of the battery to which the positive electrode prepared according to the Examples and Comparative Examples is applied, and Figure 4B is the 2C charge of the battery to which the positive electrode prepared according to the Examples and Comparative Examples is applied. It is a graph measuring the discharge capacity after discharge.

The discharge capacities of FIGS. 4A and 4B are numerically shown in Table 1 below.

division 1C 2C 1st 140th 1st 140th discharge capacity
(mAh/g) Capacity retention rate
(%) discharge capacity
(mAh/g) Capacity retention rate
(%) discharge capacity
(mAh/g) Capacity retention rate
(%) discharge capacity
(mAh/g) Capacity retention rate
(%) Example 1 162.3 100 121.9 74.9 149.7 100 121.0 80.8 Comparative Example 1 157.9 100 87.9 55.5 149.1 100 77.7 52.1 Comparative Example 2 179.7 100 29.9 16.7 162.4 100 58.14 35.7 Comparative Example 3 137.3 100 120.0 87.4 126.1 100 99.1 78.6 Comparative Example 4 166.0 100 95.3 57.4 152.3 100 85.5 56.1

As shown in Figures 4a, 4b and Table 1, the battery prepared with the positive electrode prepared according to Example 1 of the present invention had a discharge capacity and capacity retention rate after 140 cycles at 1C and 2C compared to Comparative Examples 1 to 4 It was confirmed that it was excellent.

On the other hand, Comparative Examples 1, 2 and 4 confirmed that the discharge capacity and capacity retention rate after 140 cycles at 1C and 2C were low, and in particular, Comparative Example 3 had excellent discharge capacity and capacity retention rate after 140 cycles at 1C, but at 2C. After 140 cycles, it was confirmed that the discharge capacity and capacity retention rate were rapidly lowered and thus unstable.

Test Example 3. 1C, SEM after 140 cycles

5A is a photograph taken by SEM of the cross-section (electrolyte side) of the electrode after 140 cycles at 1C of the battery to which the positive electrode prepared according to Example 1 is applied, and FIG. 5B is the positive electrode prepared according to Comparative Example 1 is applied. The cross-section of the electrode (current collector side) at 1C of the battery is a photograph taken by SEM, and FIG. 5C is a cross-section of the electrode after 140 cycles at 1C of the battery to which the positive electrode prepared according to Comparative Example 2 is applied (electrolyte side) ) is a photograph taken by SEM, and FIG. 5d is a photograph taken by SEM of the cross-section (current collector side) of the electrode after 140 cycles at 1C of the battery to which the positive electrode prepared according to Comparative Example 2 is applied.

As shown in FIGS. 5A to 5D , cracks were not observed in the electrode of Example 1, but cracks were observed in the LiNi _0.8 Co _0.1 Mn _0.1 O ₂ layer of the battery of Comparative Example 1 on the surface, In the battery, it was confirmed that cracks were observed in all _{of the LiNi 0.8} Co _0.1 Mn _0.1 O _{2 particles.}

Since cracks were not observed in the electrode of Example 1, it seems that performance improvement such as high capacity and long life was induced.

Test Example 4. 2C, SEM after 90 cycles

6A is a photograph taken by SEM of the cross-section (electrolyte side) of the electrode after 90 cycles at 2C of the battery to which the positive electrode prepared according to Example 1 is applied, and FIG. 6B is the positive electrode prepared according to Comparative Example 1 is applied. The cross-section of the electrode (current collector side) after 90 cycles at 2C of the battery is a photograph taken by SEM, and FIG. 6c is a cross-section of the electrode after 90 cycles at 2C of the battery to which the positive electrode prepared according to Comparative Example 2 is applied (electrolyte side) ) is a photograph taken by SEM, and FIG. 6d is a photograph taken by SEM of the cross-section (current collector side) of the electrode after 90 cycles at 2C of the battery to which the positive electrode prepared according to Comparative Example 2 is applied.

As shown in FIGS. 6A to 6D , cracks were not observed in the electrode of Example 1, but cracks were observed in the LiNi _0.8 Co _0.1 Mn _0.1 O ₂ layer on the surface of the battery of Comparative Example 1, and in Comparative Example 2 In the battery, it was confirmed that cracks were observed in all _{of the LiNi 0.8} Co _0.1 Mn _0.1 O _{2 particles.}

Since cracks were not observed in the electrode of Example 1, it seems that performance improvement such as high capacity and long life was induced.

Test Example 5. Measurement of output characteristics

7 is a graph of measuring the discharge capacity after charging and discharging according to the current of the battery to which the positive electrode prepared according to Examples and Comparative Examples is applied.

As shown in FIG. 7 , it was confirmed that the battery manufactured according to Example 1 of the present invention had the best output characteristics at a high current of 5 to 10 C compared to Comparative Examples 1 to 4.

Test Example 6. Measurement of characteristics by current

8A is a graph measuring the voltage and discharge capacity for each current of the battery to which the positive electrode prepared according to Example 1 is applied, and FIG. 8B is the voltage and discharge capacity for each current of the battery to which the positive electrode prepared according to Comparative Example 1 is applied. is a graph measured, FIG. 8c is a graph measuring the voltage and discharge capacity for each current of a battery to which the positive electrode prepared according to Comparative Example 2 is applied, and FIG. 8D is a battery to which the positive electrode prepared according to Comparative Example 3 is applied It is a graph measuring the voltage and discharge capacity for each current.

As shown in FIGS. 8A to 8D , the planar surface behavior was obtained differently depending on the activity of the _{LiNi 0.8} Co _0.1 Mn _0.1 O ₂ active material generated at 4.0 V under the 5C current condition. In the case of Example 1, LiNi _0.8 Co _0.1 Mn _0.1 O ₂ A 4.0 V flat surface was clearly obtained, and a discharge capacity of 111.8 mAh/g or more was obtained, whereas in Comparative Examples 1 and 2 having the remaining electrode structures under the same current conditions, LiNi _0.8 Co _0.1 Mn _0.1 O ₂ Although a 4.0 V flat surface was seen, it was confirmed that the discharge capacity was lower than that of Example 1. In addition, in the case of Comparative Example 3, the operating voltage was increased to 4.2 V as the LCO reacted, and 103.0 mAh/g, which was also less than that of Example 1, was obtained.

This is the case of Example 1 means a high capacity is maintained _{LiNi 0 .8 Co 0 .1 Mn 0} .1 O response time higher under a high current charging / discharging condition of _Fig.

Claims (12)

delete delete delete delete delete The weight ratio of Li(Ni _x Co _y Mn _z )O ₂ particles and LiCoO ₂ particles is 60:40 to 80:20,
The Li(Ni _x Co _y Mn _z )O ₂ layer has a thickness of 20 to 40 μm, and _{the thickness of the LiCoO 2} layer is 5 to 10 μm thicker than the thickness of the Li(NixCoyMnz)O2 layer,
The Li(Ni _x Co _y Mn _z )O ₂ x is a prime number of 0.6-0.8, y is a prime number of 0.1-0.3, z is a prime number of 0.1-0.3, x + y + z = 1 A positive electrode for a lithium secondary battery, characterized in that. delete delete delete A lithium secondary battery comprising the positive electrode of claim 6 . A lithium capacitor comprising the positive electrode of claim 6 . A device comprising the anode electrode of claim 6, wherein the device is selected from the group consisting of communication equipment, an energy storage system (ESS), and a means of transportation.

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