KR102254846B1 - Novel Lithium Complex Oxide and Lithium Secondary Battery Comprising the Same - Google Patents

Abstract

The present invention provides a novel lithium composite metal oxide containing nickel (Ni), cobalt (Co), and titanium (Ti) as main components, and the lithium composite metal oxide is a positive electrode active material for lithium secondary batteries with high charging capacity and When applied with an anode active material having a high energy density and has life characteristics, the optimum performance of a lithium secondary battery can be realized. In particular, since it is possible to maintain an optimum balance with the charging/discharging efficiency of the Si-based anode active material, a high-performance lithium secondary battery The battery can be manufactured.

Description

Novel Lithium Complex Oxide and Lithium Secondary Battery Comprising the Same}

The present invention relates to a novel lithium composite metal oxide containing nickel (Ni), cobalt (Co), and titanium (Ti) as main components, and a lithium secondary battery including the same.

Lithium secondary batteries have large charging and discharging capacity, high operating potential and energy density, and excellent charging and discharging cycle characteristics, and accordingly, applications such as small household electronic devices, motorcycles, electric vehicles, and hybrid vehicles as well as portable electronic devices are rapidly applied. It is expanding.

Recently, as portable electronic devices have become popular and the demand for application to medium and large-sized devices is rapidly increasing, secondary batteries having a higher capacity for the same volume are required, and for this purpose, research on core components of lithium secondary batteries is more actively conducted. It's going on.

As is well known, one of the positive electrode active material of the core structure of the lithium secondary battery is LCO (LiCoO ₂₎ Based on the per unit volume capacity is greater LNO (LiNiO ₂₎ a but the positive electrode active material are developed, a safety problem such as ignition Because of this, it was not popularized. To solve this problem, NCA containing Ni and Co as main components and a small amount of Al was developed, and NCM (Ni-Co-Mn), which has more stability than NCA, was developed.

NCA showed superiority in capacity and output compared to NCM, but its safety was relatively poor, so NCM containing Ni, Co, and Mn as main components is most commonly used. The NCM-based positive electrode active material generally has a charging capacity of 185 to 192 mAh/g and a discharge capacity of 167 to 173 mAh/g.

In recent years, the demand for high-capacity lithium secondary batteries is constantly increasing.In the case of a conventional lithium secondary battery, when the capacity is increased, the lifespan greatly decreases. To solve this problem, when the lifespan is increased through doping or coating, the capacity decreases again. The situation has not been solved.

A negative active material, which is one of the core components of a lithium secondary battery, is also actively researching to secure better properties. In particular, in order to secure a higher capacity compared to the same volume, a lot of research is being conducted on new materials other than the conventional graphite series.

For example, a Si-based negative electrode active material is a material having a very high energy density and is in the spotlight as a new negative electrode material. While the theoretical capacity of the conventional graphite-based negative active material is about 370 mAh/g, the Si-based negative active material has a theoretical capacity of about 4,200 mAh/g, which is more than 10 times higher, and has the advantage of having a small full position with lithium and abundant reserves. Have.

However, such a Si-based negative active material is known to exhibit a charge/discharge efficiency of about 70 to 88%, which represents a large difference from the charge/discharge efficiency of about 90 to 92% of a commercially available NCM-based positive electrode active material.

In addition, in general, when evaluating the characteristics of an NCM-based positive electrode active material, a discharge capacity is important rather than a charge capacity, but from the viewpoint of energy density, the charge capacity is more important than the discharge capacity.

For this reason, even if the energy density of the negative electrode active material is improved, if the charging capacity of the positive electrode active material is small or the charge/discharge efficiency of the positive electrode and the negative electrode is not balanced, a problem arises that optimal characteristics are not implemented as a whole cell, and the lifespan If the characteristics are poor, it proceeds only in the research stage and cannot be commercialized, resulting in a problem that does not contribute to industrial development.

Therefore, there is a high need for the development of a new cathode active material material capable of solving these problems.

An object of the present invention is to solve the problems of the prior art and technical problems that have been requested from the past.

The inventors of the present application developed a new lithium composite metal oxide containing nickel, cobalt, and titanium as main components, after in-depth research and various experiments, and the positive electrode active material containing such lithium composite metal oxide has high charging capacity. It has been confirmed that the optimum performance of a lithium secondary battery can be realized when applied with a Si-based negative electrode active material that not only has over-life characteristics, but also has a high energy density but a somewhat low charge/discharge efficiency, and completes the present invention. Arrived.

In order to facilitate understanding of the present invention, the difference between the positive electrode active material and the negative electrode active material due to an imbalance in charge/discharge efficiency will be briefly described.

In general, when manufacturing lithium secondary batteries, graphite-based negative active materials are most often used. The charging/discharging efficiency of the graphite-based negative active material is about 93%, while the Si-based negative active material has a large difference of about 70-88%.

When manufacturing a lithium secondary battery by applying a positive electrode active material with a charge/discharge efficiency of 90% and a graphite negative electrode active material with a charge/discharge efficiency of 93%, the positive electrode can receive up to 90 Li after sending 100 Li to the negative electrode. , The graphite-based cathode can send up to 93 Li after receiving 100 Li. That is, 93 Li is sent from the negative electrode, but only 90 Li is received from the positive electrode, so that 3 Li is not used and discarded, so various studies are being conducted to improve the discharge capacity and charge/discharge efficiency of the positive electrode active material.

However, when manufacturing a lithium secondary battery by applying a positive electrode active material with a charge/discharge efficiency of 91% and a Si-based negative electrode active material with a charge/discharge efficiency of 88%, the positive electrode sends 100 Li to the negative electrode and then receives a maximum of 91 Li. On the other hand, the Si-based cathode can only send up to 88 Li after receiving 100 Li. In other words, a maximum of 91 Li can be received from the anode, but only up to 88 can be sent from the cathode, so the three spare capacities cannot be used and are discarded.

For this reason, no matter how high the discharge capacity and charge/discharge efficiency of the positive electrode active material is, when applied together with a Si-based negative electrode active material having low charge/discharge efficiency, more than the capability of the negative electrode active material is not used and is discarded.

After all, in order to use a Si-based negative electrode active material with high energy density, it is not a positive electrode active material with very high discharge capacity and charge/discharge efficiency, but has a high charging capacity and at the same time Si-based so that more Li can be sent to the negative electrode with high energy density. This means that a positive electrode active material with charge/discharge efficiency that can be balanced with a negative electrode active material is required.

The present applicant completed the present invention with this technical perspective, and secured high charging capacity and life characteristics through a novel lithium composite metal oxide containing nickel (Ni), cobalt (Co), and titanium (Ti) as main components. .

The lithium composite metal oxide according to the present invention satisfies at least two or more of the following characteristics measured on the basis of a coin half cell, or preferably satisfies all three characteristics. Have.

Characteristics showing a charging capacity of 235 mAh/g or more under the conditions of 0.1C 4.3V (charging) and 0.1C 3.0V (discharging);

Characteristics showing charge/discharge efficiency of 90% or less under the conditions of 0.1C 4.3V (charge) and 0.1C 3.0V (discharge); And

The characteristic that the discharge capacity retention rate of the 30th cycle is more than 90% compared to the first cycle under the conditions of 1.0C 4.3V (charge) and 1.0C 3.0V (discharge).

In the case of the charging capacity, 235 mAh/g or more is suitable for use as a high-capacity lithium secondary battery, and the charging/discharging efficiency is preferably 90% or less, more preferably 88% or less so as to be in balance with the Si-based negative electrode. In addition, it is preferable that the discharge capacity retention rate showing the life characteristics is 90% or more, and it is most preferable if all three are satisfied, but even if two or more are satisfied, it is suitable to be applied together with the Si-based negative electrode active material.

In addition, the lithium composite metal oxide according to the present invention satisfies at least two or more of the following characteristics measured based on a pouch full cell to which a Si-based negative electrode is applied, or preferably three It can have a feature that satisfies all of the features. As the Si-based negative electrode, a silicon/graphite (20:80 ratio) negative electrode active material was applied, and the negative electrode/anode capacity ratio (N/P) was set to 1.1.

Characteristics showing a charging capacity of 235 mAh/g or more under the conditions of 0.1C 4.3V (charging) and 0.1C 3.0V (discharging);

Characteristics showing a discharge capacity of 177 mAh/g or more under the conditions of 0.1C 4.3V (charge) and 0.1C 3.0V (discharge); And

The characteristic that the discharge capacity retention rate of the 30th cycle is more than 93% compared to the first cycle under the conditions of 1.0C 4.3V (charge) and 1.0C 3.0V (discharge).

In the above, the charging capacity and charging/discharging efficiency measured under the conditions of 0.1C 4.3V (charging) and 0.1C 3.0V (discharging) are the results of charging/discharging at 25°C, and 1.0C 4.3V (charging) and 1.0 The discharge capacity retention rate measured under the condition of C 3.0V (discharge) is the result of charging and discharging at 45°C.

These special properties are particularly advantageous when the lithium composite metal oxide constitutes a positive electrode active material in a lithium secondary battery using a negative electrode active material having a high energy density and relatively low charge/discharge efficiency, such as a Si-based negative electrode active material. Bar, this will be described in detail in terms of technical and microscopic as follows.

Conventionally, since the focus has been on improving the characteristics of the positive electrode active material itself without considering the characteristics of the negative electrode, it has been developed in the direction of improving the discharge capacity and charging/discharging efficiency.For this reason, negative electrodes with high energy density such as Si-based negative active materials In the case of applying, there is a problem in that the charging/discharging efficiency of the positive electrode active material is higher than that of the negative electrode, so that the balance is not balanced, and the charging capacity of the positive electrode active material is small, so that the negative active material does not play its role.

That is, the conventional positive electrode active material exhibits a high charge/discharge efficiency due to the small difference between the charge capacity and the discharge capacity. However, since the charge capacity is small and the difference in charge/discharge efficiency with the negative electrode is large, a large amount of Li ions are transferred to the negative electrode active material during charging. It was impossible to provide, and even during discharge, it was impossible to receive a large amount of Li ions from the side of the negative electrode active material.

For example, the charging/discharging efficiency of an NCM-based positive electrode active material having a charging capacity of 230.1 mAh/g and a discharge capacity of 206 mAh/g is about 90%, and a charging capacity of about 241.04 mAh/g and a charging capacity of 210.61 mAh/g as a positive electrode active material. The charge/discharge efficiency of the lithium composite metal oxide of the present invention having a discharge capacity of is 87.38%. When simply comparing charging and discharging efficiency, the NCM-based positive electrode active material seems to be better than the lithium composite metal oxide of the present invention, but when applied to a lithium secondary battery together with a Si-based negative electrode active material, the NCM-based positive electrode active material is applied to the secondary battery according to the present invention. The performance of the secondary battery to which the lithium composite metal oxide is applied is much superior, and this can be confirmed in the experimental contents described later.

In the case of Ni-rich or Ni-high NCM-based positive electrode active material with a very high Ni content, it exhibits higher charging capacity and discharge capacity than general NCM-based positive electrode active materials, but there is a problem that the lifespan characteristics are greatly reduced, and doping to solve this problem. , Coating, etc. are applied, but there is a problem in that the charging capacity and the discharging capacity are greatly reduced instead of slightly improving the life characteristics, so it is very difficult to commercialize the product. In addition, since the charging/discharging efficiency is also high, it is not well-balanced with, for example, a Si-based negative active material, which is not suitable for a next-generation secondary battery.

In consideration of this point, it is very important to balance the positive active material and the negative active material in order to realize optimal performance when viewed as a whole cell of a lithium secondary battery. In particular, when a negative active material having a very high energy density such as Si-based is applied, it is more important to improve the charging capacity than the discharge capacity of the positive electrode active material. Also, in order to balance the positive electrode active material and the negative electrode active material, the charging and discharging efficiencies of each other are similar. It is very important to fit well.

In other words, in order to maximize the performance of a lithium secondary battery, a positive electrode active material with high charging capacity and excellent lifespan characteristics is required, and furthermore, when applied with a negative electrode active material having a high energy density such as a Si-based negative electrode active material, it can be balanced. It should be able to have a charge/discharge efficiency similar to or equivalent to that of the negative active material.

In this respect, among the characteristics measured based on a coin half cell and a pouch full cell to which a Si-based negative electrode is applied, a positive electrode that simultaneously satisfies at least two or more characteristics for each criterion. An active material, and furthermore, a cathode active material that satisfies all three characteristics has not been developed yet.

On the other hand, when the lithium composite metal oxide of the present invention is used as a positive electrode active material, it satisfies at least two or more characteristics, preferably three characteristics, for each criterion among the characteristics defined above at the same time.

In this regard, the inventors of the present application have developed a lithium composite metal oxide containing nickel, cobalt, and titanium as main components in place of Mn of the conventional NCM-based positive electrode active material so as to satisfy the above characteristic conditions.

First, in order for the positive electrode active material cation to reversibly have a wide oxidation/reduction potential region within its structure and to perform fast charging/discharging or to minimize the change in the crystal structure of the positive electrode active material, a small sized cation should be selected.

It is known that the ionic radius of ^{Ni 3+ is 0.56 Å, Co 3+} is 0.55 Å, Mn ³⁺ is 0.58 Å, and Mn ⁴⁺ is 0.53 Å. Ti ⁴⁺ is known to be 0.61Å, ^{and it is similar to the ionic radius of Co 3+} and Mn ³⁺ , so it was considered not to be affected by the ionic radius when forming a layered structure.

Since the electron configuration of Ti is [Ar]3d ² 4s ² and it is a 3d transition metal, it is advantageous in terms of unit weight and capacity per unit volume due to its high electrode potential, relatively light weight, and small size compared to 4d and 5d transition metals.

In the Ni-rich cathode active material, LiNiO ₂ , the oxidation number of Ni ions is Ni ³⁺ , and the low spin electron arrangement of ^{Ni 3+ is d 7. When} electrons exist at high energy level and electrons exist at high energy level, Jahn- Teller distortion occurs. The electron configuration of Ni ^{4+ is d 6} , so there is no Jahn-Teller distortion because electrons are not placed at a high energy level. The Ni-O bond length is different between Ni ³⁺ and Ni ⁴⁺ , and for this reason, the bond of Ni-O repeatedly contracts and expands during the charging and discharging process, and the layered structure is subjected to severe stress. In addition, contact with the conductive material decreases due to repetitive expansion and contraction in the z-axis due to charging and discharging, and electrical conductivity in the electrode decreases, resulting in deterioration of electrode characteristics. Since the electron configuration of ^{Ti 3+ is d 1} and the electron configuration of ^{Ti 4+ is d 0} , it is expected that it is possible to increase structural stability by substituting a part of Ni with Ti.

As another consideration, cation mixing is a factor that makes the structure of the Ni-rich cathode active material unstable. ^{Cation mixing refers to a phenomenon in which Li +} (0.76Å) and Ni ²⁺ (0.69Å) having similar ionic radii to each other change positions to form crystals.When Li ⁺ is inserted and desorbed, the spatial layer of ^{Li + Ni 2+} present in the element acts as a resistance component, reducing charging and discharging efficiency.

The inventors of the present application considered a method of suppressing cation mixing by including Ti as one of the main components in a lithium composite metal oxide. That is, Ti ⁴⁺ (0.61Å) is ^{similar in size to Ni 2+} (0.69Å), so it is stably located at the middle point of the path where Ni ions travel, T _d (tetrahedral site), and suppresses Ni migration. It was expected to minimize mixing, and as a result, it was possible to increase the electrochemical properties by preparing a Ni-rich compound having a stable structure.

In addition, the applicant of the present invention confirmed through a number of experiments that manganese (Mn), which was used as a main component in the conventional NCM-based positive electrode active material, has a disadvantage of reducing the charging capacity while improving the life characteristics, whereas titanium (Ti) is charged. It was confirmed that there is an effect of remarkably improving the life characteristics while maintaining the capacity almost the same. Particularly, since Ti slightly reduces the discharge capacity, it is highly desirable for application to next-generation lithium secondary batteries by lowering the charging/discharging efficiency of the positive electrode active material to a level similar to that of a high energy density negative electrode active material such as Si-based negative electrode active material. Confirmed.

Based on this, a lithium composite metal oxide containing nickel, cobalt, and titanium as main components was developed, and when this lithium composite metal oxide is used as a positive electrode active material, the coin half cell and Si-based negative electrode defined above were applied. Among the characteristics measured on the basis of the full cell, it was confirmed that at least two or more, preferably, three characteristics of each criterion were satisfied at the same time.

In order to satisfy these characteristics, the lithium composite metal oxide of the present invention may have a composition including at least 82% nickel, 1% or more cobalt, and 0.5% or more titanium on a mole basis.

In some cases, when manganese (Mn) is optionally further included, the content of manganese is preferably equal to or less than the content of titanium.

As a result, the lithium composite metal oxide of the present invention contains a small amount of Co and controls the contents of Ni and Ti to control the charge capacity, discharge capacity, and charge/discharge efficiency as a positive electrode active material. In addition, when the Ni content is increased, the charging capacity increases, but the problem of structurally very unstable and thus greatly deteriorating the life characteristics was solved by applying Ti.

In one specific example, the lithium composite metal oxide may be a compound represented by Formula 1 below.

Li[Li _1-m X _m ]O ₂ (1)

In the above formula,

0<m≤1, and

X is composed of only Ni, Co, and Ti, and other inevitable impurities may be included.

m may be 0.9≦m≦1 or 0.94≦m≦1.

In a more specific example, the lithium composite metal oxide may be a compound represented by Formula 2 below.

Li[Li _1-abc Ni _a Co _b Ti _c ]O ₂ (2)

In the above formula,

0<a<1, 0<b<1, 0<c<1, a+b+c≤1, and a>b≥c or a>c>b is satisfied.

In Formula 2, the conditions of 0.82≤a<1, 0<b<0.18, 0<c<0.18 may be satisfied, or 0.9≤a<1, 0<b<0.1, 0<c<0.1, and , Or 0.94≤a<1, 0<b<0.06, 0<c<0.06.

In another specific example, the lithium composite metal oxide of the present invention may further include aluminum (Al). In this regard, the inventors of the present application additionally selected Al as an element capable of greatly improving the cation mixing inhibitory effect and thermal stability by being applied together with Ti.

Al ³⁺ has a bonding force with oxygen (Al-O) of 502 kJ/mol, which is greater than Ni-O (366 kJ/mol), Co-O (385 kJ/mol), and Mn-O (362 kJ/mol). The ionic radius is also ^{similar to Ni 3+} , Co ³⁺ , and Mn ⁴⁺ , so it is suitable as a substitution element, and is more effective in suppressing cation mixing by reducing _{V 0 (oxygen vacancy), one of the migration paths of Ni ions.} In particular, when Al is added, there is an effect of improving life characteristics as structural stability is improved.

As a result, by adding Al as another main component, it is possible to improve the life characteristics while suppressing cation mixing.

In one specific example, the lithium composite metal oxide of the present invention may be a compound represented by Formula 3 below.

Li[Li _1-abcd Ni _a Co _b Ti _c Al _d ]O ₂ (3)

In the above formula,

0<a<1, 0<b<1, 0<c<1, 0<d<1, a+b+c+d≤1,

The condition of a>b≥c+d or a>c+d>b is satisfied.

In Formula 3, the conditions of 0.82≤a<1, 0<b<0.18, 0<c+d<0.18 may be satisfied, or 0.9≤a<1, 0<b<0.1, 0<c+d< It may be 0.1, or 0.94≦a<1, 0<b<0.06, 0<c+d<0.06.

In another specific example, the lithium composite metal oxide of the present invention may further include at least one or more of other dopant (D) elements and optionally aluminum (Al) in order to further improve characteristics as a positive electrode active material, and the following formula It may be a compound represented by 4.

These dopants (D) are, for example, V, Cr, Fe, Cu, Zn, Y, Zr, Mo, W, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra , B, Si, P, Mn, Sn, La, Ce, etc. can be selected. In addition, in the lithium composite metal oxide of the present invention, since the 4th coordination element and the 6th coordination element are easily substituted with each other, it may be preferable to select at least one of the 4th and 6th coordination elements as the dopant (D). .

Li[Li _1-abcdef Ni _a Co _b Ti _c Al _d D _e ]O ₂ (4)

In the above formula,

D is V, Cr, Fe, Cu, Zn, Y, Zr, Mo, W, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, B, Si, P, Mn, It is at least one selected from the group consisting of Sn, La and Ce,

0<a<1, 0<b<1, 0<c<1, 0≤d<1, 0≤e<1, a+b+c+d+e≤1, and

The condition of a>b≥c+d+e or a>c+d+e>b is satisfied.

In Formula 4, the conditions of 0.82≦a<1, 0<b<0.18, 0<c+d+e<0.18 may be satisfied, or 0.9≦a<1, 0<b<0.1, 0<c+ d+e<0.1, 0.94≤a<1, 0<b<0.06, and 0<c+d+e<0.06. In addition, since the present invention contains titanium as a main component, it is preferable that c≥d or c≥d+e.

In the lithium composite metal oxide of the present invention described above, each element may be uniformly distributed throughout the oxide particle, or some component(s) may be distributed with a concentration gradient with respect to the remaining component(s). This concentration gradient includes both the case of a sudden change in concentration as well as a gentle change in concentration.

For example, in Formula 4, at least one of Li, Ni, Co, Ti, Al, and D may have a concentration gradient that increases or decreases with respect to the radius of the oxide particle.

The present invention also provides a positive electrode active material for a lithium secondary battery including the lithium composite metal oxide, and a lithium secondary battery including a positive electrode, a negative electrode, and an electrolyte including the positive electrode active material.

The positive electrode active material of the present invention may be composed of only the lithium composite metal oxide, or may be composed of a combination with various conventionally known lithium transition metal oxides in addition to the lithium composite metal oxide. In addition, in the positive electrode active material of the present invention, a known coating layer may be additionally added to the surface of the lithium composite metal oxide to improve physical properties. All of these examples are construed as being included in the scope of the present invention.

The negative electrode active materials constituting the negative electrode may be various, for example, lithium (Li)-based, graphite-based, tin (Sn)-based, silicon (Si)-based negative active materials, etc. are all included, preferably For the same reason as described above, the Si-based silicon/graphite (20:80 ratio) negative active material may be included.

Examples of such Si-based negative active materials include Si/A alloys such as silicon (Si), silicon oxide, Si/Li Si/Sn, and Si/C composites such as SiO-C. The silicon oxide is, for example, SiO _x (0<x<2), and in the Si/A alloy, A is Li, Sn, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Alkali metals such as Cd, B, Al, Ga, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, etc., alkaline earth metals, groups 13 to 16 elements, transition metals, rare earth elements, or It may be a combination of these.

These may be used alone or in combination of two or more. In addition, it may be used with lithium-based, graphite-based, and tin-based negative electrode actives.

Since other matters constituting the lithium secondary battery are known in the art, a description thereof will be omitted herein.

As described above, the lithium composite metal oxide according to the present invention is a positive electrode active material for a lithium secondary battery, has high charging capacity and life characteristics, and when applied together with a negative active material having a high energy density, the optimum performance of a lithium secondary battery can be realized. In particular, since it is possible to maintain an optimum balance with the charging/discharging efficiency of the Si-based negative active material, a high-performance lithium secondary battery can be manufactured.

Hereinafter, the present invention will be described in more detail with reference to some embodiments, but the scope of the present invention is not limited thereto.

[Comparative Example 1]-Ni _0.82 Co _0.11 Mn _0.07

Nickel precursor, NiSO _4, CoSO ₄ cobalt precursor, manganese precursor of MnSO _4, 82: 11: 07 was added to the water in the molar ratio of nickel-cobalt-manganese hydroxide precursor solution was prepared. The aqueous solution of sodium hydroxide was slowly added dropwise while stirring the aqueous solution to neutralize the aqueous precursor solution to precipitate _{Ni 0.82} Co _0.11 Mn _0.07 (OH) _{2 as a nickel-cobalt hydrate.} LiOH was mixed in a molar ratio of 1.02 to the thus obtained precursor, and then calcined at 785° C. for 30 hours in an oxygen atmosphere to prepare a positive electrode active material.

[Example 1-1]-Ni _0.9 Co _0.08 Ti _0.02

Nickel precursor, NiSO _4, CoSO ₄ cobalt _precursor, titanium precursor TiSO ₄ to 90: 8: was added to water in a molar ratio of two nickel-cobalt-titanium hydroxide precursor solution was prepared. The aqueous solution of sodium hydroxide was slowly added dropwise while stirring the aqueous solution to neutralize the aqueous precursor solution to precipitate _{Ni 0.9} Co _0.08 Ti _0.02 (OH) _{2, which is a nickel-cobalt-titanium hydrate.} LiOH was mixed in a molar ratio of 1.02 to the thus obtained precursor, and fired at 755° C. for 30 hours in an oxygen atmosphere.

[Example 1-2]-Ni _0.9 Co _0.07 Ti _0.02 Al _0.01

The nickel precursor, NiSO _4, CoSO ₄ cobalt _precursor, the titanium precursor TiSO _{4, Al 2} (SO ₄ ) ₃ as an aluminum precursor was added to water in a molar ratio of 90:7:2:1 to prepare a nickel-cobalt-titanium-aluminum oxide precursor aqueous solution. The aqueous solution of sodium hydroxide was slowly added dropwise while stirring the aqueous solution to neutralize the aqueous precursor solution to precipitate _{Ni 0.9} Co _0.07 Ti _0.02 Al _0.01 (OH) _{2, which is a nickel-cobalt-titanium-aluminum hydrate.} LiOH was mixed in a molar ratio of 1.02 to the thus obtained precursor, and fired at 755° C. for 30 hours in an oxygen atmosphere.

[Example 2-1]-Ni _0.94 Co _0.04 Ti _0.02

Nickel precursor, NiSO _4, CoSO _4, the cobalt _precursor, titanium precursor TiSO ₄ 94: 4 was added to the water in a molar ratio of two nickel-cobalt-titanium hydroxide precursor solution was prepared. The aqueous solution of sodium hydroxide was slowly added dropwise while stirring the aqueous solution to neutralize the aqueous precursor solution to precipitate _{Ni 0.94} Co _0.04 Ti _0.02 (OH) _{2, which is a nickel-cobalt-titanium hydrate.} LiOH was mixed in a molar ratio of 1.02 to the thus obtained precursor, and fired at 740° C. for 30 hours in an oxygen atmosphere.

[Example 2-2]-Ni _0.94 Co _0.03 Ti _0.02 Al _0.01

The nickel precursor, NiSO _4, CoSO ₄ cobalt _precursor, the titanium precursor TiSO _{4, Al 2} (SO ₄ ) ₃ as an aluminum precursor was added to water in a molar ratio of 94:3:2:1 to prepare an aqueous solution of a nickel-cobalt-titanium-aluminum oxide precursor. The aqueous solution of sodium hydroxide was slowly added dropwise while stirring the aqueous solution to neutralize the aqueous precursor solution to precipitate _{Ni 0.94} Co _0.03 Ti _0.02 Al _0.01 (OH) _{2, which is a nickel-cobalt-titanium-aluminum hydrate.} LiOH was mixed in a molar ratio of 1.02 to the thus obtained precursor, and fired at 740° C. for 30 hours in an oxygen atmosphere.

[Experimental Example 1]-Coin half cell experiment

95:2:3 (weight ratio) in N-methylpyrrolidone as a solvent with Super-P as a conductive material and PVdF as a binder, using the compounds synthesized in Comparative Examples and Examples as a positive electrode active material, respectively. The mixture was mixed to prepare a positive electrode active material slurry, applied on an aluminum current collector, dried at 120° C., and rolled to prepare a positive electrode.

Lithium metal was used as the positive electrode and negative electrode prepared above, and an electrode assembly was prepared by interposing a porous polyethylene film as a separator therebetween, and after placing the electrode assembly inside the battery case, an electrolyte solution was added to the inside of the battery case. Injecting to prepare a lithium secondary battery. _{At this time, as the electrolyte, a 1.0M concentration of lithium hexafluorophosphate (LiPF 6} ) dissolved in an organic solvent consisting of ethylene carbonate/dimethyl carbonate (EC/DMC mixing volume ratio=1/1) was used.

Each lithium secondary battery thus produced was charged and discharged under the conditions of 0.1C 4.3V (charge) and 0.1C 3.0V (discharge), and 1.0C 4.3V (charge) and 1.0C 3.0V (discharge) , Charging and discharging was performed 30 times under the conditions of 45°C. The results are shown in Table 1 below as Comparative Example 1 and Examples 1-1, 1-2, 2-1, and 2-2.

[Experimental Example 2]-Pouch full cell experiment

Using the compounds synthesized in Comparative Example 1 and Examples 2-1 and 2-2 as a positive electrode active material, respectively, in N-methylpyrrolidone as a solvent with Super-P as a conductive material and PVdF as a binder, 95:2 A positive electrode active material slurry was prepared by mixing at :3 (weight ratio), coated on an aluminum current collector, dried at 120° C., and rolled to prepare a positive electrode.

A silicon/graphite (20:80 ratio) negative electrode active material was used as the negative electrode together with the positive electrode prepared above, but the negative electrode/positive electrode capacity ratio (N/P) was 1.1, and the electrode was interposed with a porous polyethylene film as a separator. An assembly was prepared, the electrode assembly was placed inside an aluminum pouch, and an electrolyte was injected into the battery case to prepare a lithium secondary battery. At this time, as the electrolyte, 1.0 M concentration of lithium hexa in an organic solvent consisting of ethylene carbonate/dimethyl carbonate/ethyl methyl carbonate (EC/DMC/EMC mixing volume ratio = 1/2/1) and vinylene carbonate (VC 2 wt%). What dissolved fluorophosphate (LiPF ₆ ) was used.

For each lithium secondary battery thus produced, charging and discharging were performed under the conditions of 0.1C 4.3V (charge) and 0.1C 3.0V (discharge), and 1.0C 4.3V (charge) and 1.0C 3.0V (discharge), Charging and discharging was performed 30 times under the condition of 45°C.

The results are shown in Comparative Experimental Example 1, Experimental Example 1, and Experimental Example 2 in Table 1 below.

As shown in Table 1, the positive electrode active material according to the present invention (Examples 1-1 to 2-2) has higher charging capacity and life characteristics compared to the conventional positive electrode active material (Comparative Example 1), and has lower charging and discharging efficiency. I can confirm.

In addition, when applied together with a Si-based negative electrode through Comparative Experimental Example 1 and Experimental Examples 1 and 2, it can be confirmed that the lifespan characteristics of the positive electrode active material according to the present invention are significantly higher than that of the prior art. It can be seen that it keeps doing.

Those of ordinary skill in the field to which the present invention belongs will be able to make various applications and modifications within the scope of the present invention based on the above contents.

Claims (21)

Among the elements included in the lithium composite metal oxide, based on the sum of the moles of the remaining elements excluding 1 mole of lithium and 2 moles of oxygen, it contains 82% or more nickel, 1% or more cobalt, and 0.5% or more titanium,
Lithium composite metal oxide, characterized in that simultaneously satisfying at least two or more of the following characteristics based on a coin half cell;
Characteristics showing a charging capacity of 235 mAh/g or more under the conditions of 0.1C 4.3V (charging) and 0.1C 3.0V (discharging);
Characteristics showing charge/discharge efficiency of 90% or less under the conditions of 0.1C 4.3V (charge) and 0.1C 3.0V (discharge); And
The characteristic that the discharge capacity retention rate of the 30th cycle is more than 90% compared to the first cycle under the conditions of 1.0C 4.3V (charge) and 1.0C 3.0V (discharge). delete Among the elements included in the lithium composite metal oxide, based on the sum of the moles of the remaining elements excluding 1 mole of lithium and 2 moles of oxygen, it contains 82% or more nickel, 1% or more cobalt, and 0.5% or more titanium,
A lithium composite metal oxide that simultaneously satisfies at least two or more of the following characteristics measured based on a pouch full cell to which a Si-based negative electrode is applied:
Characteristics showing a charging capacity of 235 mAh/g or more under the conditions of 0.1C 4.3V (charging) and 0.1C 3.0V (discharging);
Characteristics showing a discharge capacity of 177 mAh/g or more under the conditions of 0.1C 4.3V (charge) and 0.1C 3.0V (discharge); And
The characteristic that the discharge capacity retention rate of the 30th cycle is more than 93% compared to the first cycle under the conditions of 1.0C 4.3V (charge) and 1.0C 3.0V (discharge). The lithium composite metal oxide according to claim 1 or 3, wherein the three properties are satisfied at the same time. delete The lithium composite metal oxide according to claim 1 or 3, which does not contain manganese (Mn). The lithium composite metal oxide according to claim 1 or 3, wherein when manganese (Mn) is optionally further included, the manganese content is less than the titanium (Ti) content. The lithium composite metal oxide according to claim 1 or 3, characterized in that it is represented by the following Formula 1:
Li[Li _1-m X _m ]O ₂ (1)
In the above formula,
0.835≤m≤1, and
X consists only of Ni, Co and Ti. The lithium composite metal oxide according to claim 1 or 3, characterized in that it is represented by the following Formula 2:
Li[Li _1-abc Ni _a Co _b Ti _c ]O ₂ (2)
In the above formula,
0.82≤a<1, 0.01≤b<1, 0.005≤c<1, a+b+c≤1,
The condition of a>b≥c or a>c>b is satisfied. The lithium composite metal oxide according to claim 9, wherein conditions of 0.82≦a<1, 0.01≦b<0.18, and 0.005≦c<0.18 are satisfied. The lithium composite metal oxide according to claim 1 or 3, further comprising aluminum (Al). The lithium composite metal oxide according to claim 11, characterized in that it is represented by the following formula (3):
Li[Li _1-abcd Ni _a Co _b Ti _c Al _d ]O ₂ (3)
In the above formula,
0.82≤a<1, 0.01≤b<1, 0.005≤c<1, 0<d<1, a+b+c+d≤1,
The condition of a>b≥c+d or a>c+d>b is satisfied. The lithium composite metal oxide according to claim 12, wherein conditions of 0.82≦a<1, 0.01≦b<0.18, and 0.005<c+d<0.18 are satisfied. The lithium composite metal oxide according to claim 1 or 3, further comprising at least one or more of other dopant elements and optionally aluminum (Al), and is represented by the following formula (4):
Li[Li _1-abcde Ni _a Co _b Ti _c Al _d D _e ]O ₂ (4)
In the above formula,
D is V, Cr, Fe, Cu, Zn, Y, Zr, Mo, W, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, B, Si, P, Mn, It is at least one selected from the group consisting of Sn, La and Ce,
0.82≤a<1, 0.01≤b<1, 0.005≤c<1, 0≤d<1, 0<e<1, a+b+c+d+e≤1, and
The condition of a>b≥c+d+e or a>c+d+e>b is satisfied. The lithium composite metal oxide according to claim 14, wherein conditions of 0.82≦a<1, 0.01≦b<0.18, and 0.005<c+d+e<0.18 are satisfied. The lithium composite metal oxide according to claim 14, wherein at least one of Li, Ni, Co, Ti, Al, and D has a concentration gradient that increases or decreases with respect to the radius of the oxide particle. A cathode active material for a lithium secondary battery comprising the lithium composite metal oxide according to claim 1 or 3. The cathode active material for a lithium secondary battery according to claim 17, wherein a coating layer is formed on the surface of the lithium composite metal oxide particles. A lithium secondary battery comprising a positive electrode, a negative electrode, and an electrolyte including the positive electrode active material according to claim 17. The lithium secondary battery of claim 19, wherein the negative electrode comprises a Si-based negative active material. The lithium secondary battery of claim 20, wherein the Si-based negative active material comprises at least one selected from the group consisting of silicon (Si), silicon oxide, Si/A alloy, and Si/C composite.