KR102108781B1 - Novel Lithium Complex Oxide and Lithium Secondary Battery Comprising the Same - Google Patents

Abstract

The present invention provides a new lithium composite metal oxide containing nickel (Ni) and titanium (Ti) as main components. The lithium composite metal oxide is a positive electrode active material for a lithium secondary battery, and has high charging capacity and life characteristics. When applied together with a negative electrode active material having a high energy density, it is possible to realize the optimum performance of the lithium secondary battery, and in particular, since it is possible to maintain the optimal balance with the charging and discharging efficiency of an Si-based negative electrode active material, it is possible to manufacture a high performance lithium secondary battery.

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) and titanium (Ti) as main components and a lithium secondary battery comprising the same.

Lithium secondary batteries have a large charge / discharge capacity, high operating potential and energy density, and excellent charge / discharge cycle characteristics. Accordingly, their application fields such as small electronic devices, motorcycles, electric vehicles, and hybrid vehicles as well as portable electronic devices are rapidly growing. It is expanding.

Recently, as portable electronic devices have become popular and the demand for application to middle- and large-sized devices has rapidly increased, a secondary battery having a higher capacity compared to the same volume is required, and for this, studies on core components of a lithium secondary battery have been more actively conducted. Is going on.

As is well known, a positive electrode active material, which is one of the core components of a lithium secondary battery, has been developed based on LCO (LiCoO ₂ ), and a larger LNO (LiNiO ₂ ) positive electrode active material per unit volume was developed, but due to safety issues such as ignition, etc. It was not popularized. To solve this, NCA with Ni and Co as a main component and a small amount of Al was developed, and NCM (Ni-Co-Mn) with more stability than NCA was developed.

NCA showed superior capacity and output compared to NCM, but it is relatively inferior in safety, so NCM containing Ni, Co, and Mn as its main components is most commonly used. It is common for the NCM-based positive electrode active material to have 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 a high capacity lithium secondary battery has been continuously increasing. In the case of a conventional lithium secondary battery, when the capacity is increased, the service life is greatly reduced, and in order to solve this, when the life is increased through doping, coating, etc., the capacity is greatly reduced again. The situation is not being solved.

The negative active material, which is one of the core components of the lithium secondary battery, is also actively researched to secure better properties. Particularly, in order to secure a higher capacity compared to the same volume, many studies have been conducted on new materials other than the conventional graphite series.

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

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

In addition, in general, when evaluating the properties of the NCM-based positive electrode active material, the discharge capacity, not the charge capacity, is important. From the energy density point of view, the charge capacity rather than the discharge capacity is more important.

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, the problem that optimal characteristics are not realized when viewed in the whole cell occurs, and the life span If the characteristics are inferior, it only proceeds in the research stage and does not actually commercialize, resulting in a problem that does not contribute to industrial development.

Therefore, there is a high need for the development of a new positive electrode active material that can solve these problems.

The present invention aims to solve the problems of the prior art as described above and the technical problems requested from the past.

The inventors of the present application developed a new lithium composite metal oxide containing nickel and titanium as the main components after extensive research and various experiments, and the positive electrode active material containing such a lithium composite metal oxide has a high charging capacity and life. It has been confirmed that it is possible to realize optimum performance of a lithium secondary battery when it is applied together with a Si-based negative electrode active material having characteristics of not only having characteristics, but also having high energy density but somewhat low charging and discharging efficiency, and to complete the present invention.

In order to help the understanding of the present invention, differences between charging and discharging efficiency imbalance between the positive electrode active material and the negative electrode active material will be briefly described.

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

When a lithium secondary battery is manufactured by applying a positive electrode active material having a charge / discharge efficiency of 90% and a graphite-based negative electrode active material having a charge / discharge efficiency of 93%, the positive electrode can receive up to 90 Li after sending 100 Li to the negative electrode. , Graphite-based cathode can send up to 93 Li after receiving 100 Li. That is, since 93 Li is sent from the cathode, but only 90 are received from the cathode, 3 Li is not used and is discarded. Various studies have been conducted to improve the discharge capacity and charge / discharge efficiency of the cathode active material.

However, when a lithium secondary battery is manufactured by applying a positive electrode active material having a charge and discharge efficiency of 91% and a Si-based negative electrode active material having a charge and discharge efficiency of 88%, the positive electrode receives 100 Li to the negative electrode and receives up to 91 Li. On the other hand, the Si-based cathode can receive up to 88 Li after receiving 100 Li. In other words, it is possible to receive up to 91 Li from the positive electrode, but only 3 can be used and discarded because the negative electrode can send up to 88.

For this reason, even if the discharge capacity and charge / discharge efficiency of the positive electrode active material are increased, when applied together with the Si-based negative active material having low charge / discharge efficiency, more than the ability of the negative electrode active material is discarded without being used.

In the end, in order to use the Si-based negative active material having a high energy density, the Si-based material has a high charging capacity so that more Li can be sent to the negative electrode having a higher energy density than the positive electrode active material having a very high discharge capacity and charge / discharge efficiency. It means that a positive electrode active material having a charge / discharge efficiency capable of balancing the negative electrode active material is required.

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

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

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

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

Under the conditions of 1.0C 4.3V (charge) and 1.0C 3.0V (discharge), the discharge capacity retention rate of the 30th cycle compared to the first cycle is 90% or more.

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 and discharging efficiency is preferably 90% or less, more preferably 88% or less so as to balance the Si-based anode. In addition, the discharge capacity retention rate indicating the life characteristic is preferably 90% or more, and it is most preferable if all three are satisfied, but it is suitable to be applied together with the Si-based anode active material even if two or more are satisfied.

In addition to this, the lithium composite metal oxide according to the present invention simultaneously satisfies at least two or more properties among the following properties measured based on a pouch full cell to which a Si-based anode is applied, or preferably three It may have a characteristic that satisfies all the characteristics. 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 conditions of 0.1C 4.3V (charge) and 0.1C 3.0V (discharge);

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

Under the conditions of 1.0C 4.3V (charge) and 1.0C 3.0V (discharge), the discharge capacity retention rate of the 30th cycle compared to the first cycle is 93% or more.

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 and discharging at 25 ° C, 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 characteristics, particularly when the lithium composite metal oxide is a lithium secondary battery using a negative electrode active material having a high energy density and a relatively low charge / discharge efficiency, such as a Si-based negative electrode active material, exerts an advantage particularly when forming a positive electrode active material As described above, this will be described in detail from the technical to microscopic aspects.

Conventionally, since focusing on improving the characteristics of the positive electrode active material itself without considering the characteristics of the negative electrode, it has been developed in a direction to improve the discharge capacity and charge / discharge efficiency, and for this reason, a negative electrode having a high energy density, such as a Si-based negative electrode active material When applying, the charging and discharging efficiency of the positive electrode active material is significantly 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 electrode active material has a problem.

That is, in the conventional positive electrode active material, the difference between the charging capacity and the discharging capacity is small, and thus the charge and discharge efficiency is high, but since the charge capacity is small and the difference between the charge and discharge efficiency with the negative electrode is large, a large amount of Li ions toward the negative electrode active material is charged during charging. It was impossible to provide, and it was impossible to receive a large amount of Li ions from the negative electrode active material side even during discharge.

For example, the charge and discharge efficiency of the 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 249.88 mAh / g and a charging capacity of 218 mAh / g as the positive electrode active material. The lithium composite metal oxide of the present invention having a discharge capacity has a charge and discharge efficiency of 87.24%. If only the charging and discharging efficiency is compared, the NCM-based positive electrode active material appears to be better than the lithium composite metal oxide of the present invention, but when applied to a lithium secondary battery together with the Si-based negative electrode active material, the present invention is more effective than the secondary battery to which the conventional NCM-based positive electrode active material is applied. According to the lithium composite metal oxide according to the performance of the secondary battery is much superior, which can be confirmed in the experiments described later.

In the case of a Ni-rich or Ni-high positive electrode active material having a very high Ni content, it exhibits a higher charging capacity and a discharging capacity than a typical NCM-based positive electrode active material, but has a problem in that its lifespan characteristics are significantly reduced. Although technologies such as the above are applied, there is a problem in that the charging capacity and the discharging capacity are greatly reduced instead of slightly improving the lifespan characteristics, and thus, it is very difficult to actualize the product. In addition, since the charging and discharging efficiency is also high, it is not suitable for a high-density negative electrode such as a Si-based negative electrode active material, and is not suitable for a next-generation secondary battery.

Considering this, it is very important to balance the positive electrode active material and the negative electrode active material in order to realize optimal performance when viewed from the whole cell of the lithium secondary battery. In particular, when a negative electrode active material having a very high energy density such as Si is applied, it is more important to improve the charging capacity than the discharge capacity of the positive electrode active material, and the charge and discharge efficiency of each other is similar to balance the positive electrode active material and the negative electrode active material. It is very important to fit.

That is, in order to maximize the performance of the lithium secondary battery, a positive electrode active material having a high charging capacity and excellent life characteristics is required, and furthermore, when applied together 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 charge-discharge efficiency similar to or equivalent to that of the negative electrode active material.

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

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

In this regard, the inventors of the present application, in order to satisfy the above-mentioned characteristic conditions, use lithium composite metal oxides containing nickel (Ni) and titanium (Ti) as main components in place of Co and Mn of the conventional NCM-based positive electrode active material. Developed.

First, in order to minimize the change in the crystal structure of the positive electrode active material in order to minimize the change in crystal structure of the positive electrode active material, the positive and negative electrode active material has a reversibly wide oxidation / reduction potential region in the structure.

It is known that the ion radius of Ni ³⁺ is 0.56 mm 2, Co ³⁺ is 0.55 mm 2, Mn ³⁺ is 0.58 mm 2, and Mn ⁴⁺ is 0.53 mm 2. Ti ⁴⁺ and Al ³⁺ are known to be 0.61 Å and 0.54 각각, respectively, and are similar to the ionic radii of Co ³⁺ and Mn ³⁺ , and are considered not to be affected by the ionic radii when forming a layered structure.

Since the electron arrangement of Ti is [Ar] 3d ² 4s ² and is a 3d transition metal, the electrode potential is higher, the weight is relatively lighter and the size is smaller than the 4d and 5d transition metals, which is advantageous in terms of unit weight and capacity per unit volume.

In the Ni-rich positive electrode active material, LiNiO ₂ , the oxidation number of Ni ion is Ni ³⁺ , and the low spin electron arrangement of Ni ³⁺ is d ⁷ , where electrons are present at high energy level and electrons are present at high energy level. Teller distortion occurs. The electron arrangement of Ni ⁴⁺ is d ⁶ , so no electrons are placed at the high energy level, so Jahn-Teller distortion does not occur. When Ni ³⁺ and Ni ⁴⁺ have different Ni-O bond lengths, for this reason, as the Ni-O bond repeatedly contracts and expands during charging and discharging, the layered structure experiences severe stress. In addition, due to repeated expansion and contraction to the z-axis due to charging and discharging, contact with a conductive material is reduced, and thus electrical conductivity at the electrode is lowered, thereby deteriorating electrode characteristics. Since the electron arrangement of Ti ³⁺ is d ¹ and the electron arrangement of Ti ⁴⁺ is d ⁰ , it is expected that it is possible to improve structural stability by substituting part of Ni for Ti.

Another consideration is cation mixing as an element that destabilizes the structure of the Ni-rich positive electrode active material. Cation mixing space is Li ^+, when the bar means that the phenomenon is an ionic radius similar to each other Li ⁺ (0.76Å) and Ni ²⁺ (0.69Å) is changed to achieve the determined position of each other, the Li ⁺ insertion and desorption layer Ni ²⁺ present in the electrode acts as a resistive component, thereby reducing charging and discharging efficiency.

The inventors of the present application have considered a method of suppressing cation mixing by including Ti as one of the main components in a lithium composite metal oxide. That is, since Ti ⁴⁺ (0.61 Å) is similar to Ni ²⁺ (0.69,), it is stably located at the intermediate point of the path through which Ni ions travel (T _d (tetrahedral site), thereby inhibiting Ni migration, cation It was expected to minimize mixing, and as a result, it was possible to improve the electrochemical properties by preparing a stable structured Ni-rich compound.

In addition, the applicant has confirmed through a number of experiments that manganese (Mn), which was used as a main component in a conventional NCM-based positive electrode active material, has a disadvantage of improving a lifespan characteristic while reducing a charging capacity, while titanium (Ti) is charged. It was confirmed that there is an effect of dramatically improving the life characteristics while maintaining the capacity almost the same. In particular, since Ti slightly reduces the discharge capacity, it is rather desirable to apply the charge / discharge efficiency of the positive electrode active material to a level similar to that of the high energy density negative electrode active material, such as Si-based negative electrode active material, to be applied to next-generation lithium secondary batteries. Confirmed.

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

To satisfy these characteristics, the lithium composite metal oxide of the present invention may have a composition including 82% or more of nickel and 0.5% or more of titanium on a molar basis.

In some cases, when selectively further comprising at least one of cobalt (Co) and manganese (Mn), the total content of the cobalt and manganese is preferably less than the content of titanium (Ti).

As a result, the lithium composite metal oxide of the present invention can control the charge capacity, discharge capacity, and charge / discharge efficiency as a positive electrode active material by adjusting Ni and Ti contents. In addition, when the Ni content was increased, the problem of significantly decreasing the lifespan characteristics due to structurally unstable while increasing the filling capacity 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 and Ti, and other unavoidable 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-ab Ni _a Ti _b ] O ₂ (2)

In the above formula,

The conditions of 0 <a <1, 0 <b <1, a + b≤1 and a> b are satisfied.

In Formula 2, 0.82≤a <1, 0 <b≤0.18 may be satisfied, or 0.9≤a <1, 0 <b≤0.1, or 0.94≤a <1, 0 <b≤ 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 screened Al as an element that can be applied together with Ti to greatly improve the cation mixing suppression effect and thermal stability.

Al ³⁺ has a bonding strength 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). Ion 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), which is one of the movement paths of Ni ions. Particularly, when Al is added, irreversible phase transitions are suppressed, and as a result, structural stability is improved, and thus life characteristics are improved.

As a result, Al can be added as another main component, thereby improving lifetime 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-abc Ni _a Ti _b Al _c ] O ₂ (3)

In the above formula,

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

a> b≥c or a> c> b.

In Chemical Formula 3, 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, and 0 <c <0.06.

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

Such dopants (D) are, for example, Co, Mn, V, Cr, Fe, Cu, Zn, Y, Zr, Mo, W, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr , Ba, Ra, B, Si, P, Sn, La, Ce, and the like. Also, in the lithium composite metal oxide of the present invention, since the 4th and 6th coordination elements are easily substituted with each other, the dopant (D) may preferably select one or more of the 4th and 6th coordination elements. .

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

In the above formula,

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

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

a> b≥c + d or a> c + d> b.

In Chemical Formula 4, 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, and 0≤c + d <0.06. In addition, since the present invention includes titanium as a main component, it is preferable that b≥c or b≥c + d.

In the lithium composite metal oxide of the present invention described above, each element may be uniformly distributed over the entire oxide particle, and some component (s) may be distributed with a concentration gradient with respect to the other component (s). This concentration gradient includes all cases in which not only a modest concentration change but also a sudden concentration change is exhibited.

For example, in Chemical Formula 4, one or more elements of Li, Ni, Ti, Al, and D may have a concentration gradient that increases or decreases with respect to the radius of the oxide particles.

The present invention also provides a lithium secondary battery comprising a positive electrode active material for a lithium secondary battery comprising the lithium composite metal oxide, and a positive electrode, a negative electrode and an electrolyte containing such a 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 various lithium transition metal oxides known in the art 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 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 (graphite) -based, tin (Sn) -based, silicon (Si) -based negative electrode active materials, and the like are all included. For example, silicon / graphite (20:80 ratio) negative electrode active material in the Si system may be included for the same reason as described above.

Examples of the Si-based negative electrode 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, alkaline earth metals, Group 13 to 16 elements, transition metals, rare earth elements or It can be a combination of these.

These may be used alone or in combination of two or more. It can also be used with lithium-based, graphite-based, and tin-based negative electrode active materials.

Other matters constituting the lithium secondary battery are known in the art, and 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, and has high charging capacity and life characteristics, and can be implemented with lithium secondary battery optimal performance when applied with a negative electrode active material having a high energy density. In particular, since it is possible to maintain an optimal balance between charging and discharging efficiency of the Si-based negative electrode active material, it is possible to manufacture a high-performance lithium secondary battery.

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: 7, was added to the water in the molar ratio of the nickel-cobalt-manganese hydroxide precursor solution was prepared. The aqueous precursor solution was neutralized by stirring the aqueous solution while slowly dropping the sodium hydroxide aqueous solution while stirring to precipitate the nickel-cobalt hydrate Ni _0.82 Co _0.11 Mn _0.07 (OH) ₂ . The thus obtained precursor was mixed with LiOH in a molar ratio of 1.02 and calcined at 785 ° C. for 30 hours in an oxygen atmosphere to prepare a positive electrode active material.

[Example 1-1]-Ni _0.94 Ti _0.06

① A nickel-titanium hydroxide precursor aqueous solution was prepared by adding NiSO _{4 as a} nickel precursor and TiSO ₄ as a titanium precursor to water at a molar ratio of 94:06. The aqueous precursor solution was neutralized by stirring the aqueous solution while slowly dropping the sodium hydroxide aqueous solution while stirring to precipitate the nickel-titanium hydrate Ni _0.94 Ti _0.06 (OH) ₂ . LiOH was mixed in the precursor thus obtained to a molar ratio of 1.02 and calcined at 755 ° C. for 30 hours in an oxygen atmosphere.

② A nickel-titanium hydroxide precursor aqueous solution was prepared by adding NiSO _{4 as a} nickel precursor and TiSO ₄ as a titanium precursor to water at a molar ratio of 98:02. The aqueous precursor solution was neutralized by stirring the aqueous solution while slowly dropping the aqueous sodium hydroxide solution while stirring to precipitate nickel _0.98 Ti _0.02 (OH) ₂ , a nickel-titanium hydrate. LiOH was mixed in the precursor thus obtained to a molar ratio of 1.02, and TiO ₂ was further added at a molar ratio of 0.04 and calcined at 740 ° C. for 30 hours in an oxygen atmosphere.

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

① NiSO ₄ , a nickel precursor, TiSO ₄ , a titanium precursor, An aluminum precursor Al ₂ (SO ₄ ) ₃ was added to the water in a molar ratio of 94: 4: 2 to prepare a nickel-titanium-aluminum oxide precursor aqueous solution. The aqueous precursor solution was neutralized by stirring the aqueous solution while slowly dropping the sodium hydroxide aqueous solution while stirring to precipitate the nickel-titanium-aluminum hydrate Ni _0.94 Ti _0.04 Al _0.02 (OH) ₂ . LiOH was mixed in the precursor thus obtained to a molar ratio of 1.02 and calcined at 740 ° C. for 30 hours in an oxygen atmosphere.

② A nickel-titanium-aluminum hydroxide precursor aqueous solution was prepared by adding NiSO _{4 as a} nickel precursor, TiSO _{4 as a} titanium precursor, and Al ₂ (SO ₄ ) ₃ as an aluminum precursor to water at a molar ratio of 96:02:02. The precursor aqueous solution was neutralized by stirring the aqueous solution while slowly dropping the sodium hydroxide aqueous solution while stirring to precipitate the nickel-titanium hydrate Ni _0.96 Ti _0.02 Al _0.02 (OH) ₂ . LiOH was mixed in the precursor thus obtained to a molar ratio of 1.02, and further added in a 0.02 molar ratio of TiO ₂ and calcined at 740 ° C. for 30 hours in an oxygen atmosphere.

[Example 2-1]-Ni _0.98 Ti _0.02

A nickel-titanium hydroxide precursor aqueous solution was prepared by adding NiSO _{4 as a} nickel precursor and TiSO ₄ as a titanium precursor to water at a molar ratio of 98: 2. The aqueous precursor solution was neutralized by stirring the aqueous solution while slowly dropping the aqueous sodium hydroxide solution while stirring to precipitate nickel _0.98 Ti _0.02 (OH) ₂ , a nickel-titanium hydrate. LiOH was mixed with the precursor thus obtained at a molar ratio of 1.02, and calcined at 730 ° C. for 30 hours in an oxygen atmosphere.

[Example 2-2]-Ni _0.98 Ti _0.01 Al _0.01

Nickel precursor NiSO ₄ , titanium precursor TiSO ₄ , An aluminum precursor Al ₂ (SO ₄ ) ₃ was added to the water in a molar ratio of 98: 1: 1 to prepare a nickel-titanium-aluminum oxide precursor aqueous solution. The precursor aqueous solution was neutralized by stirring the aqueous solution while slowly dropping the sodium hydroxide aqueous solution while stirring to precipitate Ni _0.98 Ti _0.01 Al _0.01 (OH) ₂ , a nickel-titanium-aluminum hydrate. LiOH was mixed in the precursor thus obtained to a molar ratio of 1.02 and calcined at 730 ° 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 together with Super-P as a conductive material and PVdF as a binder, respectively, using the compounds synthesized in the Comparative Examples and Examples as a positive electrode active material, respectively. Mixing with to prepare a positive electrode active material slurry, which was coated on an aluminum current collector, dried at 120 ° C., and rolled to prepare a positive electrode.

A lithium electrode is used as a negative electrode together with the positive electrode prepared above, and an electrode assembly is prepared by interposing a porous polyethylene film that is a separator therebetween, and the electrode assembly is placed inside the battery case, and then the electrolyte is introduced into the battery case. Was injected to prepare a lithium secondary battery. At this time, as an electrolytic solution, a solution in which 1.0 M concentration of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in an organic solvent composed of ethylene carbonate / dimethyl carbonate (EC / DMC mixing volume ratio = 1/1) was used.

Charging and discharging were performed under the conditions of 0.1C 4.3V (charge) and 0.1C 3.0V (discharge) for each of the lithium secondary batteries thus produced, and also 1.0C 4.3V (charge) and 1.0C 3.0V (discharge). , 30 charge and discharge was performed under the conditions of 45 ℃. 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

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

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

Charging and discharging were performed under the conditions of 0.1C 4.3V (charge) and 0.1C 3.0V (discharge) for each of the lithium secondary batteries thus prepared, 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 Table 1 below as Comparative Experimental Example 1, Experimental Example 1, and Experimental Example 2.

As shown in Table 1, the positive electrode active material (Examples 1-1 to 2-2) according to the present invention has a higher charging capacity and lifespan characteristics compared to the conventional positive electrode active material (Comparative Example 1) and has lower charging and discharging efficiency. Can be confirmed.

In addition, it can be seen that the life characteristics of the positive electrode active material according to the present invention are significantly higher when applied together with the Si-based negative electrode through Comparative Experimental Examples 1 and 1 and 2, as well as high charging capacity. You can see that it keeps it.

Those skilled in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above.

Claims (21)

As a main component, it contains 82% or more of nickel (Ni) and 0.5% or more of titanium (Ti) on a mole basis.
A lithium composite metal oxide characterized by satisfying the properties of (a) and (b) or the properties of (a) and (b) and (c) among the following properties based on the coin half cell :
(a) characteristics showing a charging capacity of 235 mAh / g or more under conditions of 0.1C 4.3V (charge) and 0.1C 3.0V (discharge);
(b) 0.1C 4.3V (charge) and 0.1C 3.0V (discharge) under the conditions of exhibiting a charge and discharge efficiency of 90% or less; And
(c) The characteristics of the discharge capacity retention rate of the 30th cycle over 90% compared to the first cycle under the conditions of 1.0C 4.3V (charge) and 1.0C 3.0V (discharge). delete As a main component, it contains 82% or more of nickel (Ni) and 0.5% or more of titanium (Ti) on a mole basis.
Among the following properties measured based on a pouch full cell to which a Si-based negative electrode is applied, the properties of (a ') and (b') or (a ') and (b') and (c ') Lithium composite metal oxide satisfying properties:
(a ') characteristics showing a charging capacity of 235 mAh / g or more under conditions of 0.1C 4.3V (charging) and 0.1C 3.0V (discharging);
(b ') characteristics showing a discharge capacity of 177 mAh / g or more under conditions of 0.1C 4.3V (charge) and 0.1C 3.0V (discharge); And
(c ') A characteristic in which the discharge capacity retention rate of the 30th cycle compared to the first cycle is 93% or more 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 simultaneously satisfied. delete The lithium composite metal oxide according to claim 1 or 3, wherein at least one of cobalt (Co) and manganese (Mn) is not included. The method according to claim 1 or 3, wherein when the content of the cobalt (Co) and manganese (Mn) is further included, the total content of the cobalt and manganese is less than the content of the titanium (Ti). Lithium composite metal oxide. The lithium composite metal oxide according to claim 1 or 3, which is represented by the following Chemical Formula 1:
Li [Li _1-m X _m ] O ₂ (1)
In the above formula,
0.825≤m≤1, and
X consists of Ni and Ti only. The lithium composite metal oxide according to claim 1 or 3, which is represented by the following Chemical Formula 2:
Li [Li _1-ab Ni _a Ti _b ] O ₂ (2)
In the above formula,
The conditions of 0.82≤a <1, 0.005≤b <1, a + b≤1 and a> b are satisfied. The lithium composite metal oxide according to claim 9, wherein the conditions of 0.82≤a <1 and 0.005≤b≤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, which is represented by the following Chemical Formula 3:
Li [Li _1-abc Ni _a Ti _b Al _c ] O ₂ (3)
In the above formula,
0.82≤a <1, 0.005≤b <1, 0 <c <1, a + b + c≤1,
a> b≥c or a>c> b. The lithium composite metal oxide according to claim 12, wherein the conditions of 0.82≤a <1, 0.005≤b <0.18, and 0 <c <0.18 are satisfied. The lithium composite metal oxide according to claim 1 or 3, further comprising at least one of other dopant elements and optionally aluminum (Al), and represented by the following Chemical Formula 4:
Li [Li _1-abcd Ni _a Ti _b Al _c D _d ] O ₂ (4)
In the above formula,
D is Co, Mn, V, Cr, Fe, Cu, Zn, Y, Zr, Mo, W, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, B, Si, One or more selected from the group consisting of P, Sn, La and Ce,
0.82≤a <1, 0.005≤b <1, 0≤c <1, 0≤d <1, a + b + c + d≤1,
a> b≥c + d or a> c + d> b. The lithium composite metal oxide according to claim 14, wherein the conditions of 0.82≤a <1, 0.005≤b≤0.18, and 0≤c + d <0.18 are satisfied. The lithium composite metal oxide according to claim 14, wherein at least one of the elements of Li, Ni, Ti, Al and D has a concentration gradient that increases or decreases with respect to the radius of the oxide particles. A positive electrode active material for a lithium secondary battery comprising the lithium composite metal oxide according to claim 1 or 3. The positive electrode active material for a lithium secondary battery according to claim 17, wherein a coating layer is formed on the particle surface of the lithium composite metal oxide. A lithium secondary battery comprising a positive electrode, a negative electrode and an electrolyte comprising the positive electrode active material according to claim 17. The lithium secondary battery according to claim 19, wherein the negative electrode comprises a Si-based negative electrode active material. 21. The lithium secondary battery according to 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.