KR102604921B1 - Lithium transition metal oxide, positive electrode additive for lithium secondary battery, lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to lithium transition metal oxide, a positive electrode additive for lithium secondary batteries, and a lithium secondary battery containing the same. According to the present invention, a lithium transition metal oxide is provided that can suppress the generation of gas during charging and discharging of a lithium secondary battery by minimizing side reactions with electrolyte.

Description

Lithium transition metal oxide, positive electrode additive for lithium secondary battery, and lithium secondary battery containing same {LITHIUM TRANSITION METAL OXIDE, POSITIVE ELECTRODE ADDITIVE FOR LITHIUM SECONDARY BATTERY, LITHIUM SECONDARY BATTERY COMPRISING THE SAME}

The present invention relates to lithium transition metal oxide, a positive electrode additive for lithium secondary batteries, and a lithium secondary battery containing the same.

As power consumption increases along with the multifunctionalization of electronic devices, there are many attempts to increase the capacity of lithium secondary batteries and improve their charge and discharge efficiency.

As an example, a cathode active material containing 80% or more Ni is applied to the cathode of a lithium secondary battery, and a metal or metal-based anode active material such as SiO, Si, or SiC is applied to the anode, and a carbon-based anode active material such as natural graphite or artificial graphite is applied to the anode. A technology applied together with has been proposed.

Metal and metal oxide-based anode active materials enable higher capacity than carbon-based anode active materials. However, since metal and metal oxide-based negative electrode active materials have a much larger volume change during charging and discharging than graphite, it is difficult to increase the content of metal and metal oxide in the negative electrode to more than 15%. In addition, when metal and metal oxide are added to the negative electrode, an irreversible reaction occurs during initial charging and discharging, and the loss of lithium is greater than when a carbon-based negative electrode active material is used. Therefore, when metal and metal oxide-based negative electrode active materials are applied, the amount of lithium lost increases as the capacity of the battery increases, and the decrease in initial capacity also increases due to this.

Accordingly, various methods have been studied to increase the capacity of lithium secondary batteries or reduce the irreversible capacity. One of them is prelithiation, a concept that replenishes the lithium consumed in the formation of the SEI layer (solid electrolyte interphase layer) in the battery in the initial state.

Various methods have been proposed for pre-lithiation in batteries.

As an example, this is a method of electrochemically lithiating the cathode in advance before driving the battery. However, the lithiated cathode is very unstable in the air, and the electrochemical lithiation method has difficulty in scaling up the process.

Another example is a method of coating a negative electrode with lithium metal or lithium silicide (Li _x Si) powder. However, since the powder has high reactivity and thus reduces atmospheric stability, it is difficult to establish suitable solvents and process conditions when coating the cathode.

A method of preliminary lithiation at the anode includes coating more cathode material equal to the amount of lithium consumed at the cathode. However, due to the low capacity of the cathode material itself, the amount of added cathode material increases, and the energy density and capacity per weight of the final battery decrease as the amount of cathode material increases.

Accordingly, a material suitable for preliminary lithiation of a battery at the anode must have irreversible characteristics such that lithium is desorbed at least twice as much as existing anode materials during the first charge and does not react with lithium during subsequent discharge. Additives that satisfy these conditions are called sacrificial positive electrode materials.

In the case of a commercial battery, after injecting electrolyte into a case containing a stacked anode, separator, and cathode, it first goes through a formation process to perform a charge/discharge operation. During this process, an SEI layer formation reaction occurs on the cathode, and gas is generated due to decomposition of the electrolyte. In the formation process, the sacrificial cathode material releases lithium and reacts with the electrolyte as it decomposes, and gases such as N ₂ , O ₂ , and CO ₂ generated in the process are recovered through a gas pocket removal process.

As the sacrificial positive electrode material, over-lithiated positive electrode materials, which are metal oxides rich in lithium, are widely used. As the over-lithiated positive electrode materials, Li ₆ CoO ₄ , Li ₅ FeO ₄ , and Li ₆ MnO ₄ , which have an anti-fluorite structure, are well known. Their theoretical capacities are 977 mAh/g for Li ₆ CoO ₄ , 867 mAh/g for Li ₅ FeO ₄ , and 1001 mAh/g for Li ₆ MnO ₄ , which has a capacity sufficient to be used as a sacrificial anode material. Among them, Li ₆ CoO ₄ has the best electrical conductivity and has good electrochemical properties for use as a sacrificial anode material.

Li ₆ CoO ₄ is separated and decomposed step by step during the formation process, causing the crystal phase to collapse, and O ₂ gas is inevitably generated in this process. Ideally, Li ₆ CoO ₄ should not generate additional gas during charge and discharge cycles after the formation process. If gas continues to be generated during charging and discharging, the pressure inside the battery may increase, increasing the distance between electrodes and reducing battery capacity and energy density. In severe cases, there is a possibility that the battery cannot withstand the pressure and bursts, causing an explosion.

Therefore, there is a need to develop a technology that can deactivate or stabilize the final crystalline phase of Li ₆ CoO ₄ so that it is not electrochemically active so that additional gas is not generated during charge and discharge cycles.

Republic of Korea Patent Publication No. 10-2013-0079109 (2013.07.10) Republic of Korea Patent Publication No. 10-2020-0066048 (2020.06.09)

The present invention is to provide a lithium transition metal oxide that can suppress side reactions with electrolyte and alleviate gas generation at the positive electrode of a lithium secondary battery.

The present invention is intended to provide a method for producing the lithium transition metal oxide.

The present invention is to provide a positive electrode additive for lithium secondary batteries containing the lithium transition metal oxide.

The present invention is to provide a positive electrode for a lithium secondary battery containing the transition metal oxide.

The present invention is to provide a positive electrode for a lithium secondary battery including the positive electrode additive for a lithium secondary battery.

And, the present invention is to provide a lithium secondary battery including the positive electrode for the secondary battery.

According to one embodiment of the invention,

Lithium cobalt oxide containing heterogeneous elements,

The heterogeneous elements include 4th period transition metals; and one or more selected from the group consisting of group 2 elements, group 13 elements, group 14 elements, 5-period transition metals, and 6-period transition metals.

Lithium transition metal oxide is provided.

According to another embodiment of the invention,

A first step of solid-phase mixing of lithium oxide, cobalt oxide, and heteroelement oxide; and

A second step of obtaining the lithium transition metal oxide by calcining the mixture obtained in the first step under an inert atmosphere and a temperature of 550 °C to 750 °C.

A method for producing the lithium transition metal oxide is provided, including.

According to another embodiment of the invention,

A positive electrode additive for a lithium secondary battery containing the lithium transition metal oxide is provided.

According to another embodiment of the invention,

A positive electrode for a lithium secondary battery is provided, including a positive electrode active material, a binder, a conductive material, and the lithium transition metal oxide.

According to another embodiment of the invention,

A positive electrode for a lithium secondary battery is provided, including a positive electrode active material, a binder, a conductive material, and a positive electrode additive for the lithium secondary battery.

According to another embodiment of the invention,

Anode for the lithium secondary battery; cathode; separation membrane; A lithium secondary battery comprising an electrolyte is provided.

Hereinafter, the lithium transition metal oxide, the manufacturing method of the lithium transition metal oxide, the positive electrode additive for a lithium secondary battery, the positive electrode for a lithium secondary battery, and the lithium secondary battery according to embodiments of the invention will be described in more detail.

Terms or words used in this specification and claims should not be construed as limited to their usual or dictionary meanings, and the inventor may appropriately define the concept of terms in order to explain his or her invention in the best way. It must be interpreted with meaning and concept consistent with the technical idea of the invention based on the principle that it exists.

Unless otherwise defined in this specification, all technical and scientific terms have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. The terminology used in the description herein is merely to effectively describe specific embodiments and is not intended to limit the invention.

As used herein, singular forms include plural forms unless phrases clearly indicate the contrary.

As used herein, the meaning of "comprising" is to specify a specific characteristic, area, integer, step, operation, element, and/or component, and to specify another specific property, area, integer, step, operation, element, component, and/or group. It does not exclude the existence or addition of .

Since the present invention can be subject to various changes and can take various forms, specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to a specific disclosed form, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope above.

In this specification, for example, when the positional relationship between two parts is described as 'on top', 'on top', 'on the bottom', 'next to', etc., it is called 'immediately' or 'directly'. One or more other parts may be placed between the two parts unless an expression is used.

In this specification, for example, when a temporal relationship is described as 'after', 'successfully', 'next to', 'before', etc., the expressions 'immediately' or 'directly' are not used. Cases that are not consecutive may also be included.

In this specification, the term 'at least one' should be understood to include all possible combinations from one or more related items.

The term “cathode additive” used in this specification refers to a material that has irreversible properties in which lithium is desorbed at least twice as much as existing cathode materials during initial charging of a battery and does not react with lithium during subsequent discharge. The positive electrode additive may also be referred to as sacrificial positive electrode materials. Since the positive electrode additive compensates for the loss of lithium, the capacity of the battery increases by restoring the lost capacity of the battery, and by suppressing gas generation, it prevents the battery from exploding, improving the lifespan characteristics and safety of the battery. It can be improved.

The term “crystalline phase stabilization” used herein refers to suppressing the oxidation of amorphous CoO ₂ that occurs after initial charging of a lithium secondary battery containing a lithium cobalt oxide-based positive electrode additive into which a heterogeneous element is introduced. By suppressing the oxidation property of the amorphous CoO ₂ , side reactions between CoO ₂ and the electrolyte can be prevented and the generation of gas can be suppressed.

I. Lithium transition metal oxide

According to one embodiment of the invention,

Lithium cobalt oxide containing heterogeneous elements,

The heterogeneous elements include 4th period transition metals; and one or more selected from the group consisting of group 2 elements, group 13 elements, group 14 elements, 5-period transition metals, and 6-period transition metals.

Lithium transition metal oxide is provided.

As a result of the present inventors' continued research, lithium transition metal oxides introduced with two or more heterogeneous elements satisfying the above composition can minimize side reactions with the electrolyte and suppress gas generation at the positive electrode during charging and discharging of lithium secondary batteries. It was confirmed that it was possible to secure excellent battery performance. This is expected to be due to the introduction of two or more heterogeneous elements satisfying the above composition into the lithium transition metal oxide to maintain a more stable crystal phase and minimize the decrease in initial charge capacity. Accordingly, the lithium transition metal oxide makes it possible to improve the safety and lifespan characteristics of lithium secondary batteries.

Since the lithium transition metal oxide contains two or more heterogeneous elements that satisfy the above composition, it is possible to stabilize the crystal phase compared to lithium cobalt oxide such as Li ₆ CoO ₄ . In the present invention, stabilization of the crystal phase means suppressing the oxidation of amorphous CoO ₂ formed after initial charging of a lithium secondary battery containing lithium cobalt oxide.

In this regard, when a lithium secondary battery containing Li ₆ CoO ₄ is fully charged and the crystalline phase of the electrode is confirmed through X-ray diffraction (XRD), there is a tendency for there to be no amorphous pattern. In the formation process, Li ₆ CoO ₄ initially oxidizes Co ²⁺ cations to Co ⁴⁺ cations, and then gas is generated by oxidation of O ^2- anions. When charging is completed, the composition becomes CoO ₂ (Co ⁴⁺ ), but in this composition, no pattern is observed because it does not exhibit crystallinity.

In the case of Co ⁴⁺ cations, when left as is or when discharged (reduction reaction), they have a high oxidation tendency to be reduced to Co ²⁺ cations or Co ³⁺ cations, so a side reaction occurs while oxidizing the surrounding electrolyte. Due to the side reaction, electrolytes such as carbonates are decomposed and gases such as CO ₂ , CO, and H ₂ are generated. As the charge/discharge cycle progresses, the Co ²⁺ cations or Co ³⁺ cations that were reduced during charging are oxidized to Co ⁴⁺ cations, and when discharging, the Co ⁴⁺ cations are reduced again to Co ²⁺ cations or Co ³⁺ cations. , Gas is continuously generated by the above side reaction.

In order to suppress these side reactions, it is necessary to suppress the oxidation property of Co ⁴⁺ cations, which is their tendency to reduce. For example, there is a method of stabilizing the oxidation number of Co ⁴⁺ cations by introducing heterogeneous elements.

In the lithium transition metal oxide, the effect of lowering the average oxidation number of Co ⁴⁺ cations can be expected by introducing a heterogeneous element that can have a fixed oxidation number during charging and discharging of the battery. Accordingly, the oxidation of Co ⁴⁺ cations can be suppressed, and the generation of gas due to the side reaction can be suppressed.

However, as the amount of heterogeneous elements that may have a fixed oxidation number increases during charging and discharging of the battery, the initial charging capacity may relatively decrease and electrical conductivity may tend to decrease. Therefore, by introducing a 4th period transition metal as the main element of the heterogeneous element and also introducing a sub-element that can complement the electrochemical properties of the main element, it is possible to secure excellent battery performance while expressing the stabilization effect of the crystal phase. It may be possible.

The lithium transition metal oxide has a composition in which two or more different elements are alloyed or doped into Li ₆ CoO ₄ .

Here, the “alloy” means that the heterogeneous element is introduced in an amount of 10 mol% or more based on all metal elements excluding lithium in the lithium transition metal oxide. In addition, the term “doping” means that the heterogeneous element is introduced in an amount of less than 10 mol% based on the total metal elements excluding lithium in the lithium transition metal oxide.

The lithium transition metal compound includes a 4th period transition metal as a main element among the heterogeneous elements.

In addition, the lithium transition metal compound includes one or more elements selected from the group consisting of Group 2 elements, Group 13 elements, Group 14 elements, 5-period transition metals, and 6-period transition metals as sub-elements among the heterogeneous elements.

Specifically, the 4th period transition metal includes one or more selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn.

And, the group 2 element includes one or more types selected from the group consisting of Mg, Ca, Sr, and Ba; The group 13 elements include at least one selected from the group consisting of Al, Ga, and In; The group 14 elements include at least one selected from the group consisting of Si, Ge, and Sn; The 5th period transition metal includes one or more selected from the group consisting of Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, and Cd; The 6th period transition metal includes one or more selected from the group consisting of Lu, Hf, Ta, W, Re, Os, Ir, Pt, and Au.

Preferably, in terms of ease of alloying or doping with lithium cobalt oxide and stabilization of the crystal phase, the main element among the heterogeneous elements may include Zn, a 4th period transition metal; The sub-element may include one or more elements selected from the group consisting of Al, Mg, Ti, Zr, Nb, and W.

Zn, Al, Mg, Ti, Zr, Nb, and W have the property of being substituted for Co in the lattice structure of anti-fluorite, a crystal phase of Li ₆ CoO ₄ , while their own oxidation number does not change. For example, Zn has a Li ₆ ZnO ₄ crystal phase, can easily form an alloy with Li ₆ CoO ₄ , and its oxidation state does not change from 2+, so it can effectively suppress the oxidation of Co ⁴⁺ cations after initial charging. You can.

The heterogeneous element may be selected by considering whether it can exist within the anti-fluorite lattice structure of lithium cobalt oxide and whether it has a fixed oxidation number during charging and discharging of the battery.

As an example, among the 4th period transition metals, Zn has a Li ₆ ZnO ₄ crystalline phase, can easily form an alloy with Li ₆ CoO ₄ , and its oxidation state does not change from 2+, so after initial charging, the Co ⁴⁺ cation Oxidation can be effectively suppressed.

As another example, in the case of Li ₅ FeO ₄ and Li ₆ MnO ₄ that do not meet the above composition, an anti-fluorite lattice structure may be formed. However, Mn has multiple oxidation states of 2+, 3+, 4+, and 7+, and Fe has multiple oxidation states of 2+ and 3+. Accordingly, when the raw materials of the lithium cobalt oxide, such as CoO, MnO, and Fe ₂ O ₃ , are mixed and then fired, Mn or Fe is oxidized and the Co ²⁺ cation is reduced, forming Co ⁰ instead of the anti-fluorite lattice structure of the single crystal. , that is, Co metal can be produced. Even if a single crystal phase of alloyed Li ₆ CoO ₄ is created, it may be difficult to suppress the oxidation of Co ⁴⁺ cations after initial charging because the oxidation number of Mn or Fe easily changes within the operating voltage.

In the lithium transition metal oxide, the heterogeneous element may be included in an amount of 5 mol% to 80 mol% based on all metal elements excluding lithium.

In order to realize the effect of stabilizing the crystal phase, the content of the heterogeneous element is preferably 5 mol% or more based on the total metal elements excluding lithium. However, if an excessive amount of a heterogeneous element is introduced, the electrical conductivity of the lithium transition metal oxide may decrease, resulting in increased electrode resistance and poor battery performance. Therefore, it is preferable that the content of the heterogeneous element is 80 mol% or less based on the total metal elements excluding lithium.

Specifically, the content of the heterogeneous element is 5 mol% or more, or 10 mol% or more, or 15 mol% or more, based on all metal elements excluding lithium; And it may be 80 mol% or less, or 70 mol% or less, or 60 mol% or less.

Preferably, the content of the heterogeneous element is 10 mol% to 80 mol%, or 10 mol% to 70 mol%, or 15 mol% to 70 mol%, or 15 mol% to 15 mol%, based on all metal elements excluding lithium. It may be 60 mole%.

Furthermore, within the content range of the heterogeneous element, in the group consisting of the main element (4th period transition metal) and the sub element (group 2 element, group 13 element, group 14 element, 5th period transition metal, and 6th period transition metal) The content ratio of one or more selected elements) can be determined.

As an example, the 4th period transition metal among the heterogeneous elements may be included in the lithium transition metal oxide in an amount of 10 mol% to 70 mol% based on all metal elements excluding lithium.

In order to realize the effect of stabilizing the crystal phase, the content of the 4th period transition metal in the lithium transition metal oxide is preferably 10 mol% or more based on the total metal elements excluding lithium. However, if an excessive amount of a heterogeneous element is introduced, the electrical conductivity of the lithium transition metal oxide may decrease, resulting in increased electrode resistance and poor battery performance. Therefore, it is preferable that the content of the 4th period transition metal in the lithium transition metal oxide is 70 mol% or less based on the total metal elements excluding lithium.

Specifically, the content of the 4th period transition metal in the lithium transition metal oxide is 10 mol% or more, or 15 mol% or more, or 20 mol% or more, based on all metal elements excluding lithium; And it may be 70 mol% or less, or 50 mol% or less, or 30 mol% or less.

Preferably, the content of the 4th period transition metal in the lithium transition metal oxide is 10 mol% to 70 mol%, or 15 mol% to 70 mol%, or 15 mol% to 50 mole, based on all metal elements excluding lithium. %, or 20 mol% to 50 mol%, or 20 mol% to 30 mol%.

The stabilization effect of the crystal phase of the lithium transition metal oxide can be expected to be proportional to the content of the heterogeneous element. However, as the introduction amount of heterogeneous elements such as electrochemically inactive Zn increases, the initial charge capacity may relatively decrease and electrical conductivity may tend to decrease.

Therefore, it is preferable that the content of the sub-elements among the heterogeneous elements is 1 mol% or more based on the total metal elements excluding lithium.

However, if an excessive amount of a heterogeneous element is introduced, the electrical conductivity of the lithium transition metal oxide may decrease, resulting in increased electrode resistance and poor battery performance. Therefore, it is preferable that the content of the sub-element in the lithium transition metal oxide is 20 mol% or less based on the total metal elements excluding lithium.

Specifically, the content of the sub-element in the lithium transition metal oxide is 1 mol% or more, 2 mol% or more, or 3 mol% or more based on all metal elements excluding lithium; And it may be 20 mol% or less, or 17 mol% or less, or 15 mol% or less.

Preferably, the content of the sub-element in the lithium transition metal oxide is 1 mol% to 20 mol%, or 2 mol% to 20 mol%, or 2 mol% to 17 mol%, based on all metal elements excluding lithium. , or 3 mol% to 17 mol%, or 3 mol% to 15 mol%.

The lithium transition metal oxide may be represented by the following formula (1):

[Formula 1]

Li ₆ Co _1-xy Zn _x M _y O ₄

In Formula 1,

M is a group 2 element, a group 13 element, a group 14 element, a 5-period transition metal, or a 6-period transition metal,

x is 0.1 to 0.7,

y is 0.01 to 0.2.

Preferably, in Formula 1, M may be one or more elements selected from the group consisting of Al, Mg, Ti, Zr, Nb, and W.

In Formula 1, x is 0.1 to 0.7, and y is 0.01 to 0.2.

Specifically, x is 0.1 or more, or 0.15 or more, or 0.2 or more; And it may be 0.7 or less, or 0.5 or less, or 0.3 or less. Preferably, x may be 0.1 to 0.7, or 0.15 to 0.7, or 0.15 to 0.5, or 0.2 to 0.5, or 0.2 to 0.3.

The y is 0.01 or more, or 0.02 or more, or 0.03 or more; And it may be 0.2 or less, or 0.17 or less, or 0.15 or less. Preferably, y may be 0.01 to 0.2, or 0.02 to 0.2, or 0.02 to 0.17, or 0.03 to 0.17, or 0.03 to 0.15.

And, in Formula 1, the x+y value is 0.05 or more, or 0.10 or more, or 0.15 or more, or 0.20 or more; And it may be desirable to be 0.80 or less, or 0.70 or less, or 0.60 or less, or 0.50 or less.

That is, in order to demonstrate the crystal phase stabilization effect of the lithium transition metal oxide, the x+y value in Formula 1 is preferably 0.05 or more, 0.10 or more, 0.15 or more, or 0.20 or more. However, if the x+y value is too large, the electrical conductivity of the lithium transition metal oxide may decrease and battery performance may decrease. Therefore, it is preferable that the x+y value in Formula 1 is 0.80 or less, or 0.70 or less, or 0.60 or less, or 0.50 or less.

Specifically, in Formula 1, the x+y value may be 0.05 to 0.80, or 0.10 to 0.80, or 0.15 to 0.80, or 0.15 to 0.70, or 0.15 to 0.60, or 0.20 to 0.60, or 0.20 to 0.50.

Preferably, the lithium transition metal oxide is Li ₆ Co _0.77 Zn _0.2 Al _0.03 O ₄ , Li ₆ Co _0.76 Zn _0.2 Al _0.04 O ₄ , Li ₆ Co _0.75 Zn _0.2 Al _0.05 O ₄ , Li ₆ Co _0.7 Zn _0.25 Al _0.05 O ₄ , Li ₆ Co _0.65 Zn _0.25 Al _0.1 O ₄ , Li ₆ Co _0.67 Zn _0.3 Al _0.03 O ₄ , Li ₆ Co _0.66 Zn _0.3 Al _0.04 O ₄ , Li ₆ Co _0.65 Zn _0.3 Al _0.05 O ₄ , Li ₆ Co _0.6 Zn _0.3 Al _0.1 O ₄ , Li ₆ Co _0.77 Zn _0.2 Mg _0.03 O ₄ , Li ₆ Co _0.76 Zn _0.2 Mg _0.04 O ₄ , Li ₆ Co _0.75 Zn _0.2 Mg _0.05 O ₄ , Li ₆ Co _0.7 Zn _0.25 Mg _{0. 05} O ₄ , Li ₆ Co _0.67 Zn _0.3 Mg _0.03 O ₄ , Li ₆ Co _0.66 Zn _0.3 Mg _0.04 O ₄ , Li ₆ Co _0.65 Zn _0.3 Mg _0.05 O ₄ , Li ₆ Co _0.77 Zn _0.2 Ti _0.03 O ₄ , Li ₆ Co _0.76 Zn _0.2 Ti _0.04 O ₄ , Li ₆ Co _0.75 Zn _0.2 Ti _0.05 O ₄ , Li ₆ Co _0.72 Zn _0.25 Ti _{0.03 O 4 , Li 6 Co 0.67 Zn 0.3 Ti 0.03 O 4} , Li ₆ Co _0.66 Zn _0.3 Ti _0.04 O ₄ , Li ₆ Co _0.65 Zn _0.3 Ti _0.05 O ₄ , Li ₆ Co _0.77 Zn _0.2 Zr _0.03 O ₄ , Li ₆ Co _0.76 Zn _0.2 Zr _0.04 O ₄ , Li ₆ Co _0.75 Zn _0.2 Zr _0.05 O ₄ , Li ₆ Co _0.72 Zn _0.25 Zr _0.03 O ₄ , Li ₆ Co _0.67 Zn _0.3 Zr _0.03 O ₄ , Li ₆ Co _0.66 Zn _0.3 Zr _0.04 O ₄ , Li ₆ Co _0.65 Zn _0.3 Zr _0.05 O ₄ , Li ₆ Co _0.77 Zn _0.2 Nb _0.03 O ₄ , Li ₆ Co _0.76 Zn _0.2 Nb _0.04 O ₄ , Li ₆ Co _0.75 Zn _0.2 Nb _0.05 O ₄ , Li ₆ Co _0.67 Zn _0.3 Nb _0.03 O ₄ , Li ₆ Co _0.66 Zn _0.3 Nb _0.04 O ₄ , Li ₆ Co _0.65 Zn _0.3 Nb _0.05 O ₄ , Li ₆ Co _0.77 Zn _0.2 W _0.03 O ₄ , Li ₆ Co _0.76 Zn _0.2 W _0.04 O ₄ , Li ₆ Co _0.75 Zn _0.2 W _0.05 O ₄ , Li ₆ Co _0.67 Zn _0.3 W _0.03 O ₄ , It may include one or more compounds selected from the group consisting of Li ₆ Co _0.66 Zn _0.3 W _0.04 O ₄ , and Li ₆ Co _0.65 Zn _0.3 W _0.05 O ₄ .

The lithium transition metal oxide has the property of irreversibly releasing lithium during charging and discharging of a lithium secondary battery. In particular, the lithium transition metal oxide suppresses side reactions with the electrolyte, making it possible to improve the safety and lifespan characteristics of lithium secondary batteries.

II. Method for producing lithium transition metal oxide

According to another embodiment of the invention,

A first step of solid-phase mixing of lithium oxide, cobalt oxide, and heteroelement oxide; and

A second step of obtaining the lithium transition metal oxide by calcining the mixture obtained in the first step under an inert atmosphere and a temperature of 550 °C to 750 °C.

A method for producing the lithium transition metal oxide is provided, including.

In the first step, a raw material mixture containing lithium oxide, cobalt oxide, and heteroelement oxide is prepared.

As the lithium oxide, an oxide containing lithium, such as Li ₂ O, may be used without particular limitation.

Additionally, as the cobalt oxide, an oxide containing cobalt, such as CoO, may be used without particular limitation.

Details regarding the heterogeneous elements are described in 『I. Replaced with the information described in the section ‘Lithium transition metal oxide’.

The heterogeneous element oxides include 4-period transition metal oxides; and oxides of one or more elements selected from the group consisting of Group 2 elements, Group 13 elements, Group 14 elements, 5-period transition metals, and 6-period transition metals. As a non-limiting example, oxides containing the heterogeneous elements such as ZnO, Mg, Al ₂ O ₃ , TiO ₂ , ZrO ₂ , Nb ₂ O ₅ , and WO ₃ may be used without particular limitation. .

The raw material mixture is 『I. It is prepared by solid-phase mixing the lithium oxide, the cobalt oxide, and the heterogeneous element oxide to match the stoichiometric ratio described in “Lithium transition metal oxide.”

In the second step, the lithium transition metal oxide is obtained by calcining the raw material mixture obtained in the first step in an inert atmosphere and at a temperature of 550 °C to 750 °C.

The second step may be performed under an inert atmosphere formed using inert gases such as Ar, N ₂ , Ne, and He.

In the second step, it is preferable to heat the mixture obtained in the first step at a temperature increase rate of 1.4 °C/min to 2.0 °C/min under an inert atmosphere to reach the calcination temperature.

If the temperature increase rate is too slow, crystal seeds may form slowly and crystal growth may continue, resulting in particles becoming too large. Therefore, it is preferable that the temperature increase rate is 1.4 °C/min or more. However, if the temperature increase rate is excessively fast, a large amount of crystal seeds are generated at a very high rate, and the growth time for the particles is relatively insufficient, so crystallinity may be relatively low and the particle size may also be relatively small. Therefore, it is preferable that the temperature increase rate is 2.0 °C/min or less.

Specifically, the temperature increase rate is 1.40 °C/min or more, or 1.45 °C/min or more, or 1.50 °C/min or more; and may be less than or equal to 2.00 °C/min, or less than or equal to 1.95 °C/min, or less than or equal to 1.90 °C/min. Preferably, the temperature increase rate is 1.40 °C/min to 2.00 °C/min, or 1.45 °C/min to 2.00 °C/min, or 1.45 °C/min to 1.95 °C/min, or 1.50 °C /min to 1.95 °C/min, or 1.50 °C/min to 1.90 °C/min.

The firing may be performed at a temperature of 550 °C to 750 °C.

In order to enable crystal seeds to be generated at an appropriate rate, the sintering temperature is preferably 550 °C or higher. However, if the sintering temperature is excessively high, sintering may occur where the grown crystal particles clump together. Therefore, it is preferable that the calcination temperature is 750 °C or lower.

Specifically, the firing temperature is 550 °C or higher, or 580 °C or higher, or 600 °C or higher; And it can be below 750 °C, or below 720 °C, or below 700 °C. Preferably, the firing temperature may be 580 °C to 750 °C, or 580 °C to 720 °C, or 600 °C to 720 °C, or 600 °C to 700 °C.

The firing may be performed for 2 to 20 hours at the firing temperature. The firing time can be adjusted by taking into account the time required for the heterogeneous element to be introduced into the lithium cobalt oxide in the form of an alloy or doping to stabilize the crystal. Specifically, the firing time is 2 hours or more, 3 hours or more, or 4 hours or more; And it can be less than 20 hours, or less than 19 hours, or less than 18 hours. Preferably, the firing time may be 3 hours to 20 hours, or 3 hours to 19 hours, or 4 hours to 19 hours, or 4 hours to 18 hours.

The lithium transition metal oxide obtained in the second step may have a cumulative 50% particle size (D50) of 1 ㎛ to 30 ㎛ as measured by laser diffraction scattering particle size distribution. If necessary, pulverizing and classifying the lithium transition metal oxide may be performed so that it falls within the range of the D50 value.

In order to prevent side reactions with the electrolyte from worsening due to too large a specific surface area, the D50 value is preferably 1 ㎛ or more. However, if the particle size is too large, it is difficult to uniformly coat the positive electrode material containing the lithium transition metal oxide on the current collector, and damage to the current collector may be caused during the drying and rolling process. Therefore, it is preferable that the D50 value is 30 ㎛ or less.

Specifically, the lithium transition metal oxide is 1 ㎛ or more, or 3 ㎛ or more, or 5 ㎛ or more; And it may have the D50 value of 30 ㎛ or less, 27 ㎛ or less, or 25 ㎛ or less. Preferably, the lithium transition metal oxide may have a D50 value of 3 ㎛ to 30 ㎛, or 3 ㎛ to 27 ㎛, or 5 ㎛ to 27 ㎛, or 5 ㎛ to 25 ㎛.

If necessary, the step of washing and drying the compound represented by Formula 1 obtained in the second step may be performed.

As a non-limiting example, the cleaning process may be performed by mixing and stirring the compound of Formula 1 and the cleaning solution at a weight ratio of 1:2 to 1:10. Distilled water, ammonia water, etc. may be used as the cleaning liquid. The drying may be performed by heat treatment at a temperature of 100 °C to 200 °C or 100 °C to 180 °C for 1 hour to 10 hours.

III. Cathode additive for lithium secondary battery

According to another embodiment of the invention,

A positive electrode additive for a lithium secondary battery containing the lithium transition metal oxide is provided.

The lithium transition metal oxide can suppress gas generation at the positive electrode during charging and discharging of a lithium secondary battery by minimizing side reactions with the electrolyte. Therefore, the positive electrode additive for lithium secondary batteries containing the lithium transition metal oxide enables improvement of safety and lifespan characteristics of lithium secondary batteries.

The positive electrode additive for a lithium secondary battery containing the lithium transition metal oxide has the property of irreversibly releasing lithium during charging and discharging of the lithium secondary battery. Therefore, the positive electrode additive for a lithium secondary battery can be included in a positive electrode for a lithium secondary battery and serve as sacrificial positive electrode materials for prelithiation.

Details regarding the lithium transition metal oxide can be found in 『I. Replaced with the information described in the section ‘Lithium transition metal oxide’.

The lithium transition metal oxide has a composition in which two or more different elements are alloyed or doped into Li ₆ CoO ₄ .

The lithium transition metal compound includes a 4th period transition metal as a main element among the heterogeneous elements.

In addition, the lithium transition metal compound includes one or more elements selected from the group consisting of Group 2 elements, Group 13 elements, Group 14 elements, 5-period transition metals, and 6-period transition metals as sub-elements among the heterogeneous elements.

Specifically, the 4th period transition metal includes one or more selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn.

And, the group 2 element includes one or more types selected from the group consisting of Mg, Ca, Sr, and Ba; The group 13 elements include at least one selected from the group consisting of Al, Ga, and In; The group 14 elements include at least one selected from the group consisting of Si, Ge, and Sn; The 5th period transition metal includes one or more selected from the group consisting of Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, and Cd; The 6th period transition metal includes one or more selected from the group consisting of Lu, Hf, Ta, W, Re, Os, Ir, Pt, and Au.

Preferably, in terms of ease of alloying or doping with lithium cobalt oxide and stabilization of the crystal phase, the main element among the heterogeneous elements may include Zn, a 4th period transition metal; The sub-element may include one or more elements selected from the group consisting of Al, Mg, Ti, Zr, Nb, and W.

In the lithium transition metal oxide, the heterogeneous elements may be included in an amount of 5 mol% to 80 mol% based on all metal elements excluding lithium.

Among the heterogeneous elements, the 4th period transition metal may be included in the lithium transition metal oxide in an amount of 10 mol% to 70 mol% based on the total metal elements excluding lithium.

Among the heterogeneous elements, one or more heterogeneous elements selected from the group consisting of group 2 elements, group 13 elements, group 14 elements, 5th period transition metals, and 6th period transition metals are all metal elements excluding lithium in the lithium transition metal oxide. On a basis, it may be included in an amount of 1 mol% to 20 mol%.

The lithium transition metal oxide may be represented by the following formula (1):

[Formula 1]

Li ₆ Co _1-xy Zn _x M _y O ₄

In Formula 1,

M is a group 2 element, a group 13 element, a group 14 element, a 5-period transition metal, or a 6-period transition metal,

x is 0.1 to 0.7,

y is 0.01 to 0.2.

Preferably, in Formula 1, M may be one or more elements selected from the group consisting of Al, Mg, Ti, Zr, Nb, and W.

Preferably, the lithium transition metal oxide is Li ₆ Co _0.77 Zn _0.2 Al _0.03 O ₄ , Li ₆ Co _0.76 Zn _0.2 Al _0.04 O ₄ , Li ₆ Co _0.75 Zn _0.2 Al _0.05 O ₄ , Li ₆ Co _0.7 Zn _0.25 Al _0.05 O ₄ , Li ₆ Co _0.65 Zn _0.25 Al _0.1 O ₄ , Li ₆ Co _0.67 Zn _0.3 Al _0.03 O ₄ , Li ₆ Co _0.66 Zn _0.3 Al _0.04 O ₄ , Li ₆ Co _0.65 Zn _0.3 Al _0.05 O ₄ , Li ₆ Co _0.6 Zn _0.3 Al _0.1 O ₄ , Li ₆ Co _0.77 Zn _0.2 Mg _0.03 O ₄ , Li ₆ Co _0.76 Zn _0.2 Mg _0.04 O ₄ , Li ₆ Co _0.75 Zn _0.2 Mg _0.05 O ₄ , Li ₆ Co _0.7 Zn _0.25 Mg _{0. 05} O ₄ , Li ₆ Co _0.67 Zn _0.3 Mg _0.03 O ₄ , Li ₆ Co _0.66 Zn _0.3 Mg _0.04 O ₄ , Li ₆ Co _0.65 Zn _0.3 Mg _0.05 O ₄ , Li ₆ Co _0.77 Zn _0.2 Ti _0.03 O ₄ , Li ₆ Co _0.76 Zn _0.2 Ti _0.04 O ₄ , Li ₆ Co _0.75 Zn _0.2 Ti _0.05 O ₄ , Li ₆ Co _0.72 Zn _0.25 Ti _{0.03 O 4 , Li 6 Co 0.67 Zn 0.3 Ti 0.03 O 4} , Li ₆ Co _0.66 Zn _0.3 Ti _0.04 O ₄ , Li ₆ Co _0.65 Zn _0.3 Ti _0.05 O ₄ , Li ₆ Co _0.77 Zn _0.2 Zr _0.03 O ₄ , Li ₆ Co _0.76 Zn _0.2 Zr _0.04 O ₄ , Li ₆ Co _0.75 Zn _0.2 Zr _0.05 O ₄ , Li ₆ Co _0.72 Zn _0.25 Zr _0.03 O ₄ , Li ₆ Co _0.67 Zn _0.3 Zr _0.03 O ₄ , Li ₆ Co _0.66 Zn _0.3 Zr _0.04 O ₄ , Li ₆ Co _0.65 Zn _0.3 Zr _0.05 O ₄ , Li ₆ Co _0.77 Zn _0.2 Nb _0.03 O ₄ , Li ₆ Co _0.76 Zn _0.2 Nb _0.04 O ₄ , Li ₆ Co _0.75 Zn _0.2 Nb _0.05 O ₄ , Li ₆ Co _0.67 Zn _0.3 Nb _0.03 O ₄ , Li ₆ Co _0.66 Zn _0.3 Nb _0.04 O ₄ , Li ₆ Co _0.65 Zn _0.3 Nb _0.05 O ₄ , Li ₆ Co _0.77 Zn _0.2 W _0.03 O ₄ , Li ₆ Co _0.76 Zn _0.2 W _0.04 O ₄ , Li ₆ Co _0.75 Zn _0.2 W _0.05 O ₄ , Li ₆ Co _0.67 Zn _0.3 W _0.03 O ₄ , It may include one or more compounds selected from the group consisting of Li ₆ Co _0.66 Zn _0.3 W _0.04 O ₄ , and Li ₆ Co _0.65 Zn _0.3 W _0.05 O ₄ .

IV. Anode for lithium secondary battery

According to another embodiment of the invention, a positive electrode for a lithium secondary battery is provided.

The positive electrode for a lithium secondary battery may include a positive electrode active material, a binder, a conductive material, and the lithium transition metal oxide.

Additionally, the positive electrode for a lithium secondary battery may include a positive electrode active material, a binder, a conductive material, and a positive electrode additive for the lithium secondary battery.

The lithium transition metal oxide and the positive electrode additive for a lithium secondary battery have the property of irreversibly releasing lithium during charging and discharging of a lithium secondary battery. Therefore, the lithium transition metal oxide and the positive electrode additive for a lithium secondary battery may be included in the positive electrode for a lithium secondary battery and serve as sacrificial positive electrode materials for prelithiation.

Preferably, the cathode for a lithium secondary battery includes a cathode material including a cathode active material, a conductive material, the sacrificial cathode material, and a binder; And, it includes a current collector that supports the positive electrode material.

Here, the sacrificial cathode material is the lithium transition metal oxide or the cathode additive for a lithium secondary battery. Details regarding the sacrificial cathode material are described in 『I. Lithium transition metal oxide』 and 『III. Replace with the information described in the section ‘Anode additives for lithium secondary batteries’.

As batteries move to higher capacity, the ratio of negative electrode active material in the negative electrode must be increased to increase battery capacity, and the amount of lithium consumed in the SEI layer accordingly increases. Therefore, the design capacity of the battery can be determined by calculating the amount of lithium consumed in the SEI layer of the cathode and then recalculating the amount of sacrificial cathode material to be applied to the anode.

According to one embodiment, the sacrificial positive electrode material may be included in an amount of more than 0% by weight and less than or equal to 15% by weight based on the total weight of the positive electrode material.

In order to compensate for the irreversible lithium consumed in forming the SEI layer, the content of the sacrificial cathode material is preferably greater than 0% by weight based on the total weight of the cathode material.

However, if the sacrificial cathode material is included in excess, the content of the cathode active material, which exhibits reversible charge/discharge capacity, is reduced, thereby reducing the capacity of the battery, and the remaining lithium in the battery is plated on the cathode, causing a short circuit or safety hazard of the battery. may hinder. Therefore, it is preferable that the content of the sacrificial cathode material is 15% by weight or less based on the total weight of the cathode material.

Specifically, the content of the sacrificial cathode material is more than 0% by weight, or more than 0.5% by weight, or more than 1% by weight, or more than 2% by weight, or more than 3% by weight, based on the total weight of the cathode material; And, it may be 15% by weight or less, or 12% by weight or less, or 10% by weight or less.

Preferably, the content of the sacrificial cathode material is 0.5% to 15% by weight, or 1% to 15% by weight, or 1% to 12% by weight, or 2% to 12% by weight, based on the total weight of the cathode material. , or 2% by weight to 10% by weight, or 3% by weight to 10% by weight.

As the positive electrode active material, compounds known to be applicable to lithium secondary batteries in the technical field to which the present invention pertains may be used without particular limitation.

As a non-limiting example, the positive electrode active material is NCM (Li[Ni,Co,Mn]O ₂ ), NCMA (Li[Ni,Co,Mn,Al]O ₂ ), LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₂ , LiNi _1-d Co _d O ₂ , LiCo _1-d Mn _d O ₂ , LiNi _1-d Mn _d O ₂ (0≤d<1), Li(Ni _a Co _b Mn _c )O ₄ (0<a<2, 0<b<2, 0<c<2, a+b+c=2), LiMn _2-e Ni _e O ₄ , LiMn _2-e Co _e O ₄ (or more 0 < e <2), LiCoPO ₄ , and LiFePO ₄ . As the positive electrode active material, one or a mixture of two or more of the examples described above may be used.

According to one embodiment, the positive electrode active material may be included in an amount of 80% to 95% by weight based on the total weight of the positive electrode material.

Specifically, the content of the positive electrode active material is 80% by weight or more, or 82% by weight, or 85% by weight or more, based on the total weight of the positive electrode material; And, it may be 95% by weight or less, or 93% by weight or less, or 90% by weight or less.

Preferably, the content of the positive electrode active material is 82% to 95% by weight, or 82% to 93% by weight, or 85% to 93% by weight, or 85% to 90% by weight, based on the total weight of the positive electrode material. It can be.

The conductive material is used to provide conductivity to the electrode.

The conductive material may be used without particular limitation as long as it has electronic conductivity without causing chemical changes in the battery. As a non-limiting example, the conductive material may include carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; Graphites such as natural graphite and artificial graphite; Metal powders or metal fibers such as copper, nickel, aluminum, and silver; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Alternatively, it may be a conductive polymer such as a polyphenylene derivative. As the conductive material, one or a mixture of two or more of the examples described above may be used.

The content of the conductive material can be adjusted within a range that does not cause a decrease in battery capacity while maintaining an appropriate level of conductivity. Preferably, the content of the conductive material may be 1% to 10% by weight or 1% to 5% by weight based on the total weight of the cathode material.

The binder is used to properly attach the positive electrode material to the current collector.

As a non-limiting example, the binder may be polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl Cellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber. (SBR), fluorine rubber, etc. As the binder, one or a mixture of two or more of the examples described above may be used.

The content of the binder can be adjusted within a range that does not cause a decrease in battery capacity while maintaining an appropriate level of adhesiveness. Preferably, the content of the binder may be 1% to 10% by weight or 1% to 5% by weight based on the total weight of the cathode material.

As the current collector, any material known in the technical field to which the present invention pertains is applicable to the positive electrode of a lithium secondary battery may be used without particular limitation.

As a non-limiting example, the current collector may include stainless steel; aluminum; nickel; titanium; calcined carbon; Alternatively, an aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. can be used.

Preferably, the current collector may have a thickness of 3 ㎛ to 500 ㎛. In order to increase the adhesion of the cathode material, the current collector may have fine irregularities formed on its surface. The current collector may have various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven fabrics.

The positive electrode for a lithium secondary battery may be formed by stacking a positive electrode material including the positive electrode active material, the conductive material, the sacrificial positive electrode material, and a binder on the current collector.

V. Lithium secondary battery

According to another embodiment of the invention,

Anode for the lithium secondary battery; cathode; separation membrane; A lithium secondary battery comprising an electrolyte is provided.

The lithium secondary battery includes a positive electrode containing the lithium transition metal oxide or a positive electrode additive for a lithium secondary battery. Accordingly, the lithium secondary battery can suppress gas generation at the charge/discharge battery positive electrode and exhibit improved safety and lifespan characteristics. In addition, the lithium secondary battery can exhibit high discharge capacity, excellent output characteristics, and capacity maintenance rate.

Accordingly, the lithium secondary battery is used in the field of portable electronic devices such as mobile phones, laptop computers, tablet computers, mobile batteries, and digital cameras; And it can be used as an energy source with improved performance and safety in the field of transportation such as electric vehicles, electric motorcycles, and personal mobility devices.

The lithium secondary battery may include an electrode assembly wound with a separator between the positive electrode and the negative electrode, and a case in which the electrode assembly is built. In addition, the anode, the cathode, and the separator may be impregnated with an electrolyte.

The lithium secondary battery may have various shapes, such as prismatic, cylindrical, or pouch-shaped.

For details regarding the anode, see 『IV. Replaced with the information described in the section ‘Anode for Lithium Secondary Battery’.

The negative electrode includes a negative electrode material including a negative electrode active material, a conductive material, and a binder; And it may include a current collector supporting the negative electrode material.

The negative electrode active material includes a material capable of reversibly intercalating and deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, and a transition metal oxide. It can be included.

Examples of materials that can reversibly intercalate and deintercalate lithium ions include crystalline carbon, amorphous carbon, or mixtures thereof as carbonaceous materials. Specifically, the carbonaceous material includes natural graphite, artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitches, mesophase pitch based carbon fiber, These may be meso-carbon microbeads, petroleum or coal tar pitch derived cokes, soft carbon, and hard carbon.

The alloy of the lithium metal is Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, Sn, Bi, Ga, and Cd. It may be an alloy of lithium and a metal selected from the group consisting of.

Materials capable of doping and dedoping lithium include Si, Si-C composite, SiOx (0<x<2), and Si-Q alloy (where Q is an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, and a group 15 It is an element selected from the group consisting of elements, group 16 elements, transition metals, rare earth elements, and combinations thereof; however, Si is excluded), Sn, SnO ₂ , Sn-R alloy (where R is an alkali metal, an alkali It may be an element selected from the group consisting of earth metals, group 13 elements, group 14 elements, group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof; however, Sn is excluded). And, as a material capable of doping and dedoping lithium, at least one of the above examples and SiO ₂ can be used in combination. Q and R are 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, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S , Se, Te, Po, etc.

And, the transition metal oxide may be vanadium oxide, lithium vanadium oxide, lithium titanium oxide, etc.

Preferably, the negative electrode may include one or more negative electrode active materials selected from the group consisting of carbonaceous materials and silicon compounds.

Here, the carbonaceous material is, as previously exemplified, natural graphite, artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch, mesophase pitch-based carbon fiber, carbon microspheres, petroleum or coal-based coke, softened carbon, and hardened carbon. It is one or more substances selected from the group consisting of. And, the silicon compound is a compound containing Si as previously exemplified, that is, Si, Si-C composite, SiOx (0<x<2), the Si-Q alloy, a mixture thereof, or at least one of these and SiO It may be a mixture of ₂ .

According to one embodiment, the negative electrode active material may be included in an amount of 85% to 98% by weight based on the total weight of the negative electrode material.

Specifically, the content of the negative electrode active material is 85% by weight or more, or 87% by weight, or 90% by weight or more, based on the total weight of the negative electrode material; And, it may be 98% by weight or less, or 97% by weight or less, or 95% by weight or less.

Preferably, the content of the negative electrode active material is 85% to 97% by weight, or 87% to 97% by weight, or 87% to 95% by weight, or 90% to 95% by weight, relative to the total weight of the negative electrode material. It can be.

Regarding the conductive material, the binder, and the current collector included in the negative electrode material, see 『IV. Replaced with the information described in the section ‘Anode for Lithium Secondary Battery’.

The separator separates the anode and cathode and provides a passage for lithium ions. As the separator, any membrane known in the technical field to which the present invention pertains is applicable to a separator of a lithium secondary battery may be used without particular limitation. The separator preferably has low resistance to ion movement in the electrolyte and has excellent wettability to the electrolyte.

Specifically, the separator may be a porous polymer film made of polyolefin-based polymers such as polyethylene, polypropylene, ethylene-butene copolymer, ethylene-hexene copolymer, and ethylene-methacrylate copolymer. The separator may be a multilayer membrane in which two or more layers of the porous polymer film are stacked. The separator may be a non-woven fabric containing glass fiber, polyethylene terephthalate fiber, etc. Additionally, the separator may be coated with a ceramic component or polymer material to ensure heat resistance or mechanical strength.

Meanwhile, the electrolyte may be used without particular limitation as long as it is known to be applicable to lithium secondary batteries in the technical field to which the present invention pertains. For example, the electrolyte may be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc.

Specifically, the electrolyte may include a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move.

Specifically, the non-aqueous organic solvent includes ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether and tetrahydrofuran; Ketone-based solvents such as cyclohexanone; Aromatic hydrocarbon solvents such as benzene and fluorobenzene; Dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and carbonate-based solvents such as propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a C2 to C20 straight-chain, branched or ring-structured hydrocarbon group, and may include a double bond aromatic ring or ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; and sulfolane.

Among the above examples, a carbonate-based solvent may be preferably used as the non-aqueous organic solvent.

In particular, considering the charge/discharge performance of the battery and compatibility with the sacrificial cathode material, the non-aqueous organic solvent may be a cyclic carbonate (e.g., ethylene carbonate, propylene carbonate) with high ionic conductivity and high dielectric constant and a low viscosity. Mixtures of linear carbonates (e.g., ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate) may be preferably used. In this case, it may be advantageous to achieve the above-mentioned performance by mixing the cyclic carbonate and the linear carbonate at a volume ratio of 1:1 to 1:9.

In addition, the non-aqueous organic solvent includes ethylene carbonate (EC) and ethyl methyl carbonate (EMC) mixed at a volume ratio of 1:2 to 1:10; Alternatively, a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 1 to 3:1 to 9:1 may be preferably used.

The lithium salt contained in the electrolyte is dissolved in the non-aqueous organic solvent and acts as a source of lithium ions in the battery, enabling the operation of a basic lithium secondary battery and promoting the movement of lithium ions between the positive electrode and the negative electrode. It plays a role.

Specifically, the lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 4 , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN( _{C 2 F 5} SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiN(SO ₂ F) ₂ (LiFSI, lithium bis(fluorosulfonyl)imide), LiCl, LiI, and LiB(C ₂ O4) It could be _2nd place. Preferably, the lithium salt may be LiPF ₆ , LiFSI, and mixtures thereof.

The lithium salt may be included in the electrolyte at a concentration of 0.1 M to 2.0 M. The lithium salt contained in the above concentration range enables excellent electrolyte performance by providing appropriate conductivity and viscosity to the electrolyte.

Optionally, the electrolyte may contain additives for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity.

For example, the additives include haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, and tria hexaphosphate. It may be mead, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, aluminum trichloride, etc. . The additive may be included in an amount of 0.1% to 5% by weight based on the total weight of the electrolyte.

The lithium transition metal oxide according to the present invention can maintain a stabilized lattice structure by introducing heterogeneous elements, thereby minimizing side reactions with the electrolyte and suppressing gas generation during charging and discharging of a lithium secondary battery. The positive electrode additive for lithium secondary batteries containing the lithium transition metal oxide enables improvement of safety and lifespan characteristics of lithium secondary batteries.

Figure 1 is a graph showing the correlation between irreversible capacity and gas generation amount of lithium secondary batteries of Examples 1 to 5 and Comparative Examples 1 to 2.
Figure 2 is a graph showing the correlation between irreversible capacity and gas generation amount of lithium secondary batteries according to Examples 6 to 12.
Figure 3 is a graph showing the capacity retention rate (cycle retention) according to the accumulation of charge and discharge cycles of the lithium secondary batteries of Example 13 and Comparative Examples 3 to 6.

Hereinafter, the operation and effect of the invention will be described in more detail through specific examples of the invention. However, this is presented as an example to aid understanding of the invention. It is not intended that the scope of the invention is limited in any way through the following examples, and it will be clear to those skilled in the art that various changes and modifications are possible within the scope and technical idea of the present invention.

Example 1

(1) Synthesis of lithium transition metal oxide

A raw material mixture was prepared by solid-phase mixing Li ₂ O, CoO, ZnO, and MgO at a molar ratio of Li:Co:Zn:Mg = 6:0.77:0.2:0.03.

The raw material mixture was heated in an Ar atmosphere at a heating rate of 1.6 °C/min for 6 hours, and then calcined at 600 °C for 12 hours to obtain a lithium transition metal oxide of Li ₆ Co _0.77 Zn _0.2 Mg _0.03 O ₄ .

The lithium transition metal oxide was crushed using a jaw crusher and classified using a sieve shaker.

(2) Lithium secondary battery manufacturing

The lithium transition metal oxide (Li ₆ Co _0.77 Zn _0.2 Mg _0.03 O ₄ ) as a positive electrode additive, carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder were mixed in an organic solvent ( N-methylpyrrolidone) was mixed to prepare a cathode material slurry. The positive electrode material slurry was applied to one side of a current collector, which was an aluminum foil with a thickness of 15 μm, and was rolled and dried to prepare a positive electrode. For reference, in this experiment, no positive electrode active material was added to the positive electrode material. The addition of the positive electrode active material is shown in Example 6 below.

A negative electrode material slurry was prepared by mixing natural graphite as a negative electrode active material, carbon black as a conductive material, and carboxymethyl cellulose (CMC) as a binder in an organic solvent (N-methylpyrrolidone) at a weight ratio of 95:3:2. The negative electrode material slurry was applied to one side of a current collector, which was a copper foil with a thickness of 15 μm, and was rolled and dried to prepare a negative electrode.

A non-aqueous organic solvent was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) at a volume ratio of 3:4:3. An electrolyte was prepared by dissolving 0.7 M concentration of LiPF ₆ and 0.5 M concentration of LiFSI, a lithium salt, in the non-aqueous organic solvent.

An electrode assembly was manufactured with a porous polyethylene separator between the anode and the cathode, and the electrode assembly was placed inside the case. A lithium secondary battery in the form of a pouch cell was manufactured by injecting the electrolyte into the case.

Example 2

A lithium secondary battery containing (1) a lithium transition metal oxide of Li ₆ Co _0.77 Zn _0.2 Al _0.03 O ₄ and (2) this as a positive electrode additive in the same manner as in Example 1, except that Al ₂ O ₃ was used instead of MgO. was manufactured.

Example 3

A lithium secondary battery containing (1) a lithium transition metal oxide of Li ₆ Co _0.77 Zn _0.2 Ti _0.03 O ₄ and (2) this as a positive electrode additive was prepared in the same manner as in Example 1, except that TiO ₂ was used instead of MgO. did.

Example 4

A lithium secondary battery containing (1) a lithium transition metal oxide of Li ₆ Co _0.77 Zn _0.2 Zr _0.03 O ₄ and (2) this as a positive electrode additive was prepared in the same manner as in Example 1, except that ZrO ₂ was used instead of MgO. did.

Example 5

In the same manner as Example 1, except that Nb ₂ O ₅ was used instead of MgO, (1) a lithium transition metal oxide of Li ₆ Co _0.77 Zn _0.2 Nb _0.03 O ₄ and (2) a lithium secondary battery containing this as a positive electrode additive. was manufactured.

Example 6

In the same manner as in Example 1, except that a solid raw material mixture of Li ₂ O, CoO, ZnO and Al ₂ O ₃ was used at a molar ratio of Li: Co: Zn: Al = 6: 0.7: 0.25: 0.05. A lithium secondary battery containing (1) Li ₆ Co _0.7 Zn _0.25 Al _0.05 O ₄ phosphorus transition metal oxide and (2) this as a positive electrode additive was manufactured.

Example 7

A lithium secondary battery containing (1) Li ₆ Co _0.7 Zn _0.25 Mg _0.05 O ₄ lithium transition metal oxide and (2) this as a positive electrode additive in the same manner as Example ₆ , except that MgO was used instead of Al ₂ O 3 was manufactured.

Example 8

(1) in the same manner as in Example 1, except that a raw material mixture of Li ₂ O, CoO, ZnO and TiO ₂ in solid phase at a molar ratio of Li: Co: Zn: Ti = 6: 0.72: 0.25: 0.03 was used. ) A lithium transition metal oxide of Li ₆ Co _0.72 Zn _0.25 Ti _0.03 O ₄ and (2) a lithium secondary battery containing this as a positive electrode additive were manufactured.

Example 9

In the same manner as Example 8, except that ZrO ₂ was used instead of TiO ₂ , (1) a lithium transition metal oxide of Li ₆ Co _0.72 Zn _0.25 Zr _0.03 O ₄ and (2) a lithium secondary battery containing this as a positive electrode additive were prepared. Manufactured.

Example 10

In the same manner as Example 1, except that a solid mixture of Li ₂ O, CoO, ZnO and Al ₂ O ₃ was used at a molar ratio of Li: Co: Zn: Al = 6: 0.65: 0.3: 0.05. A lithium secondary battery containing (1) Li ₆ Co _0.65 Zn _0.3 Al _0.05 O ₄ phosphorus transition metal oxide and (2) this as a positive electrode additive was manufactured.

Example 11

In the same manner as in Example 1, except that a raw material mixture of Li ₂ O, CoO, ZnO, and Al ₂ O ₃ was used as a solid mixture at a molar ratio of Li: Co: Zn: Al = 6: 0.65: 0.25: 0.1. A lithium secondary battery containing (1) Li ₆ Co _0.65 Zn _0.25 Al _0.1 O ₄ phosphorus transition metal oxide and (2) this as a positive electrode additive was manufactured.

Example 12

In the same manner as Example 1, except that a raw material mixture of Li ₂ O, CoO, ZnO, and Al ₂ O ₃ was used as a solid mixture at a molar ratio of Li: Co: Zn: Al = 6: 0.6: 0.3: 0.1. A lithium secondary battery containing (1) Li ₆ Co _0.6 Zn _0.3 Al _0.1 O ₄ phosphorus transition metal oxide and (2) this as a positive electrode additive was manufactured.

Example 13

A lithium secondary battery was manufactured in the same manner as Example 6, except that additional positive electrode active material was added when manufacturing the positive electrode and the composition of the negative electrode active material was changed when manufacturing the negative electrode.

Specifically, NCMA (Li[Ni,Co,Mn,Al]O ₂ )-based compound, NTA-X12M, L&F) as the positive electrode active material, and the lithium transition metal oxide (Li ₆ Co _0.7 Zn _0.25 Al _0.05 O ₄ ), carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder were mixed with an organic solvent (N-methylpyrrolidone) at a weight ratio of 93.8:1.2:3:2 to prepare a cathode material slurry. The positive electrode material slurry was applied to one side of a current collector, which was an aluminum foil with a thickness of 15 μm, and was rolled and dried to prepare a positive electrode.

A mixture of natural graphite and SiO as the negative electrode active material (weight ratio = 9:1), carbon black as the conductive material, carboxymethyl cellulose (CMC) as the binder, and organic solvent (N-methylpyrrolidone) at a weight ratio of 95:3:2. was mixed to prepare a negative electrode material slurry. The negative electrode material slurry was applied to one side of a current collector, which was a copper foil with a thickness of 15 μm, and was rolled and dried to prepare a negative electrode.

An electrode assembly was manufactured with a porous polyethylene separator between the anode and the cathode, and the electrode assembly was placed inside the case. A lithium secondary battery in the form of a pouch cell was manufactured by injecting the electrolyte into the case.

Comparative Example 1

Lithium transition metal oxide (1) Li ₆ CoO ₄ was prepared in the same manner as Example 1, except that ZnO and MgO were not added and Li ₂ O and CoO were mixed at a molar ratio of Li: Co = 6: 1. and (2) a lithium secondary battery containing this as a positive electrode additive was manufactured.

Comparative Example 2

(1) Li ₆ Co _0.7 Zn in the same manner as Example 1, except that MgO was not added and Li ₂ O, CoO and ZnO were mixed at a molar ratio of Li: Co: Zn = 6: 0.7: 0.3. A lithium secondary battery containing _0.3 O ₄ phosphorus lithium transition metal oxide (2) and this as a positive electrode additive was manufactured.

Comparative Example 3

A lithium secondary battery was manufactured in the same manner as Example 13, except that Li ₆ CoO ₄ obtained in Comparative Example 1 was used as a positive electrode additive instead of Li ₆ Co _0.7 Zn _0.25 Al _0.05 O ₄ .

Comparative Example 4

A lithium secondary battery was manufactured in the same manner as in Example 13, except that Li ₆ Co _0.7 Zn _0.3 O ₄ obtained in Comparative Example 2 was used as a positive electrode additive instead of Li ₆ Co _0.7 Zn _0.25 Al _0.05 O ₄ when manufacturing the positive electrode. Manufactured.

Comparative Example 5

When manufacturing a positive electrode _, NCMA (Li[Ni,Co _, Mn,Al]O ₂ )-based compound _{, NTA- 4} ) Instead, DN2O (Li ₂ NiO ₂ , POSCO Chemical), carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder were mixed in a weight ratio of 91.2:3.8:3:2. A lithium secondary battery was manufactured in the same manner as Example 13.

Comparative Example 6

A lithium secondary battery was manufactured in the same manner as Example 13, except that the positive electrode additive was not added when manufacturing the positive electrode.

Test example 1

For the lithium secondary batteries of Examples 1 to 12 and Comparative Examples 1 and 2, the cumulative gas generation amount according to the cumulative charge and discharge cycle was measured by the method below, and the gas generation amount according to the measured cumulative charge capacity is shown in Table 1, Figure 1 and It is shown in Figure 2. The cumulative amount of gas generated according to high temperature storage time is shown in Table 2.

(1) Measurement of formation (initial charge) capacity and charge/discharge capacity

A lithium secondary battery in the form of a pouch cell was cycled by constant current-constant voltage charging to 4.25 V at 0.1 C at 45 °C and constant current discharging to 2.5 V, resting for 20 minutes between charging and discharging, and then measuring the formation capacity and charge/discharge capacity. did.

(2) Measurement of cumulative gas generation according to charging and discharging accumulation

After operating the lithium secondary battery under the charging and discharging conditions of (1) above, the pouch cell was briefly recovered in a discharged state at the point in which the amount of gas generation was to be measured. Using a hydrometer (MATSUHAKU, TWD-150DM), the difference between the original weight of the pouch cell and the weight in water was measured and the change in volume within the pouch cell was calculated, and the change in volume was divided by the weight of the electrode active material to calculate the weight per weight. The amount of gas generated was calculated.

(3) Measurement of cumulative gas generation due to high temperature storage

A lithium secondary battery in the form of a pouch cell is charged at constant current-full voltage to 4.25 V at 0.1 C at a temperature of 45 °C, then recovered, measured for formation capacity, and stored in a 60 °C chamber. At intervals of one week, the lithium secondary battery was taken out of the chamber, the difference between the original weight of the pouch cell and the weight in water was measured using a hydrometer (MATSUHAKU, TWD-150DM), and the change in volume within the pouch cell was calculated, and the volume The amount of gas generated per weight was calculated by dividing the change by the weight of the electrode active material.

Table 1 below shows the cumulative amount of gas generated after 1 ^st , 2 ^nd , 10 ^th , 30 ^th , and 50 ^th cumulative cycles after formation (0 ^th charge/discharge).

Formation Cumulative gas generation (mL/g) Volume
(mAh/g) amount of gas generated
(mL/g) 1st 2nd 10th 30th 50th Example 1
(Li ₆ Co _0.77 Zn _0.2 Mg _0.03 O ₄ ) 805.5 95.8 -0.22 -0.28 0.07 0.39 0.56 Example 2
(Li ₆ Co _0.77 Zn _0.2 Al _0.03 O ₄ ) 746.6 85.1 -0.04 -0.14 -0.06 0.11 0.16 Example 3
(Li ₆ Co _0.77 Zn _0.2 Ti _0.03 O ₄ ) 770.3 102.5 -0.08 -0.13 0.16 0.47 0.85 Example 4
(Li ₆ Co _0.77 Zn _0.2 Zr _0.03 O ₄ ) 763.1 91.8 -0.23 -0.22 0.17 0.64 0.83 Example 5
(Li ₆ Co _0.77 Zn _0.2 Nb _0.03 O ₄ ) 771.3 92.1 -0.33 -0.16 0.11 0.58 0.89 Example 6
(Li ₆ Co _0.7 Zn _0.25 Al _0.05 O ₄ ) 822.6 113.1 -0.10 -0.14 -0.07 0.05 0.25 Example 7
(Li ₆ Co _0.7 Zn _0.25 Mg _0.05 O ₄ ) 808.6 105.6 -0.11 0.03 0.05 0.36 0.53 Example 8
(Li ₆ Co _0.72 Zn _0.25 Ti _0.03 O ₄ ) 801.0 107.0 -0.08 -0.07 0.35 0.92 0.97 Example 9
(Li ₆ Co _0.72 Zn _0.25 Zr _0.03 O ₄ ) 787.6 105.4 -0.03 -0.04 0.45 1.16 1.46 Example 10
(Li ₆ Co _0.65 Zn _0.3 Al _0.05 O ₄ ) 813.7 98.4 -0.35 -0.49 -0.16 -0.41 -0.28 Example 11
(Li ₆ Co _0.65 Zn _0.25 Al _0.1 O ₄ ) 818.3 96.5 -0.03 -0.23 0.02 -0.09 -0.06 Example 12
(Li ₆ Co _0.6 Zn _0.3 Al _0.1 O ₄ ) 807.2 96.2 -0.25 -0.19 -0.01 0.02 0.04 Comparative Example 1
(Li ₆ CoO ₄ ) 903.0 129.1 5.92 6.91 8.04 9.17 10.10 Comparative Example 2
(Li ₆ Co _0.7 Zn _0.3 O ₄ ) 827.9 105.0 -0.16 -0.19 0.44 1.68 2.11

As shown in Table 1 and Figure 1, Examples 1 to 5 had smaller initial charge capacities than Comparative Examples 1 and 2. However, the cumulative gas generation amount after the 50 ^th cycle was within 1 mL/g in all of Examples 1 to 5, showing a significantly excellent gas reduction effect. In particular, Example 1 had the largest initial charging capacity among the examples, and the cumulative amount of gas generation was relatively small. Example 2 had a somewhat low initial charge capacity, but was confirmed to have an excellent gas reduction effect as the cumulative gas generation amount was the lowest. As shown in Table 1 and Figure 2, in the case of Ti and Zr, additional gas was reduced by adding heterogeneous elements. The effect of reduction was relatively small. Referring to Examples 6, 10, 11, and 12, it was confirmed that the higher the molar content of Al, the more effective it was in reducing gas.

Table 2 below shows the cumulative amount of gas generated after 1, 2, 3, and 4 weeks of storage at 60 °C after formation ( ^0th charge/discharge).

Cumulative gas generation (mL/g) 1 week 2 weeks 3 weeks 4 weeks Example 1
(Li ₆ Co _0.77 Zn _0.2 Mg _0.03 O ₄ ) -0.46 -0.38 0.35 0.42 Example 2
(Li ₆ Co _0.77 Zn _0.2 Al _0.03 O ₄ ) -0.04 -0.04 0.69 0.56 Example 3
(Li ₆ Co _0.77 Zn _0.2 Ti _0.03 O ₄ ) -0.13 -0.01 0.44 0.42 Example 4
(Li ₆ Co _0.77 Zn _0.2 Zr _0.03 O ₄ ) -0.27 0.31 0.67 0.72 Example 5
(Li ₆ Co _0.77 Zn _0.2 Nb _0.03 O ₄ ) -0.29 0.02 0.20 0.35 Example 6
(Li ₆ Co _0.7 Zn _0.25 Al _0.05 O ₄ ) -0.52 -0.28 -0.22 -0.23 Example 7
(Li ₆ Co _0.7 Zn _0.25 Mg _0.05 O ₄ ) -0.35 -0.23 0.25 0.26 Example 8
(Li ₆ Co _0.72 Zn _0.25 Ti _0.03 O ₄ ) -0.10 0.26 0.91 1.14 Example 9
(Li ₆ Co _0.72 Zn _0.25 Zr _0.03 O ₄ ) -0.11 0.27 1.00 1.23 Example 10
(Li ₆ Co _0.65 Zn _0.3 Al _0.05 O ₄ ) -0.80 0.10 0.11 0.21 Example 11
(Li ₆ Co _0.65 Zn _0.25 Al _0.1 O ₄ ) -0.60 -0.45 -0.69 -0.08 Example 12
(Li ₆ Co _0.6 Zn _0.3 Al _0.1 O ₄ ) -0.58 -0.23 -0.17 -0.21 Comparative Example 1
(Li ₆ CoO ₄ ) 9.95 10.19 9.70 9.56 Comparative Example 2
(Li ₆ Co _0.7 Zn _0.3 O ₄ ) -0.15 -0.12 0.50 1.04

As shown in Table 2, Examples 1 to 5 were confirmed to have a significantly superior gas reduction effect compared to Comparative Examples 1 and 2, with a cumulative gas generation amount of less than 1 mL/g when stored at high temperature of 60 °C. Referring to Examples 6 to 12, it was confirmed that the lithium transition metal oxide into which Al was introduced showed an excellent effect in reducing gases in high temperature storage.

Test example 2

For the lithium secondary batteries of Example 13 and Comparative Examples 3 to 6, which were applied by mixing the positive electrode active material and the positive electrode additive, the capacity retention rate and cumulative gas generation amount according to charge and discharge cycle accumulation were measured in the following manner. The capacity maintenance rate and cumulative gas generation amount are shown in Figure 3 and Table 3.

(1) Measurement of formation (initial charge) capacity and charge/discharge capacity

A lithium secondary battery in the form of a pouch cell was cycled with constant current-constant voltage charging up to 4.25 V at 0.1 C and constant current discharging up to 2.5 V, resting for 20 minutes between charging and discharging, at a temperature of 45 °C. After that, the formation capacity and 100 ^th cycle were performed. The charge/discharge capacity up to was measured.

(2) Measurement of cumulative gas generation according to charging and discharging accumulation

After operating the lithium secondary battery under the charging and discharging conditions of (1) above, the pouch cell was briefly recovered in a discharged state at the point in which the amount of gas generation was to be measured. Using a hydrometer (MATSUHAKU, TWD-150DM), the difference between the original weight of the pouch cell and the weight in water was measured and the change in volume within the pouch cell was calculated, and the change in volume was divided by the weight of the electrode active material to calculate the weight per weight. The amount of gas generated was calculated.

(3) Measurement of cumulative gas generation due to high temperature storage

A lithium secondary battery in the form of a pouch cell is charged at constant current-full voltage to 4.25 V at 0.1 C at a temperature of 45 °C, then recovered, measured for formation capacity, and stored in a 60 °C chamber. At intervals of one week, the lithium secondary battery was taken out of the chamber, the difference between the original weight of the pouch cell and the weight in water was measured using a hydrometer (MATSUHAKU, TWD-150DM), and the change in volume within the pouch cell was calculated, and the volume The amount of gas generated per weight was calculated by dividing the change by the weight of the electrode active material.

Table 3 below shows the formation (0 ^th charge/discharge) capacity, the cumulative gas generation amount after 50 ^th and 100 ^th cumulative cycles, and the discharge capacity maintenance rate after 100 ^th cycle.

Formation capacity
(mAh/g) amount of gas generated
(mL/g) Capacity maintenance rate
@ 100th cycle Charging capacity Discharge capacity 50th 100th Example 13
(NCMA+Li ₆ Co _0.7 Zn _0.25 Al _0.05 O ₄ ) 243.5 214.8 0.05 0.07 91.7 Comparative Example 3
(NCMA+Li ₆ CoO ₄ ) 243.3 215.4 0.03 0.24 88.5 Comparative Example 4
(NCMA+Li ₆ Co _0.7 Zn _0.3 O ₄ ) 243.4 214.9 0.14 0.16 88.2 Comparative Example 5
(NCMA+DN20) 242.2 214.5 0.02 0.11 86.3 Comparative Example 6
(NCMA) 236.0 201.3 0.10 0.20 86.2

As shown in Table 3 and Figure 3, the discharge capacity of Example 13 and Comparative Examples 3 to 5 was greater than that of Comparative Example 6 in which the positive electrode additive (sacrificial positive electrode material) was not applied. This can be seen as the sacrificial anode material compensating for the irreversible lithium consumed to form the SEI layer in the cathode. On the other hand, in Comparative Example 6, since there is no sacrificial anode material to compensate for the irreversible lithium, lithium from the cathode material is consumed, reducing the discharge capacity. A decrease occurred, resulting in a discharge capacity of 201.3 mAh/g.

The cumulative gas generation amount in ^{the 100th} cycle of Example 13 was 0.07 mL/g, which was lower than 0.24 mL/g of Comparative Example 3 and 0.16 mL/g of Comparative Example 4, and Comparative Example 6 where no sacrificial cathode material was applied. This value is less than 0.20 mL/g. In Example 13, by additionally introducing Al into Li ₆ Co _0.7 Zn _0.3 O ₄ into which Zn was introduced in Comparative Example 4, CoO ₂ formed after initial charging was stabilized more effectively than when only Zn was introduced, thereby preventing side reactions with the electrolyte. This can be seen as effectively preventing and suppressing additional gas generation.

The cumulative amount of gas generation in the ^50th cycle of Comparative Example 5 was the lowest at 0.02 mL/g, but the increase in gas generation from the ^50th cycle to the ^100th cycle was 0.09 mL/g, so there is a possibility that gas generation will continue to increase thereafter. There is. This also applies to Comparative Example 3. On the other hand, in the case of Example 13, the increase in gas generation from the ^50th cycle to the ^100th cycle was 0.02 mL/g, so it can be seen that gas generation is suppressed as the charge and discharge cycle continues.

In Example 13, Comparative Example 3, and Comparative Example 4 in which the Co-based sacrificial anode material was applied, the capacity retention rate at 100 ^th cycle was found to be 88.2% or more. Comparative Example 5 in which a Ni-based sacrificial anode material was applied and Comparative Example 6 in which a sacrificial anode material was not applied had a capacity retention rate of 86.3% and 86.2%, respectively, which was significantly lower than that in Example 13. In particular, in Example 13 where Al was additionally introduced, it was confirmed that the capacity retention rate was greatly improved to 91.7%. This can be thought to be because, as seen in the accumulated gas generation amount earlier, the additional introduction of Al prevents side reactions with the electrolyte by stabilizing the crystalline phase after initial charging.

From this, when the Co-based sacrificial cathode material, especially the sacrificial cathode material having the composition of Formula 1, is applied to a lithium secondary battery containing the actual cathode material, the initial discharge capacity is preserved and the amount of gas generated in the battery is suppressed. In addition, it can be seen that the capacity maintenance rate after 100 ^th cycle is also excellent.

Table 4 below shows the cumulative amount of gas generated after 1, 2, 3, and 4 weeks of storage at 72 °C after formation ( ^0th charge).

Cumulative gas generation (mL/g) 1 week 2 weeks 3 weeks 4 weeks Example 13
(NCMA+Li ₆ Co _0.7 Zn _0.25 Al _0.05 O ₄ ) 0.09 0.12 0.12 0.15 Comparative Example 3
(NCMA+Li ₆ CoO ₄ ) 1.07 1.38 1.78 2.01 Comparative Example 4
(NCMA+Li ₆ Co _0.7 Zn _0.3 O ₄ ) 0.11 0.14 0.18 0.22 Comparative Example 5
(NCMA+DN20) 0.54 0.65 0.80 0.82 Comparative Example 6
(NCMA) 0.21 0.29 0.53 0.55

As shown in Table 4, Example 13 had the lowest cumulative gas generation amount of 0.15 mL/g after 4 weeks. This can be said to be because, similar to the charge/discharge cycle results, the heterogeneous elements introduced into Li ₆ CoO ₄ effectively stabilize CoO ₂ formed after initial charging, preventing side reactions with the electrolyte and suppressing the generation of additional gas. , Example 13 generated less gas than Comparative Example 6 in which the sacrificial cathode material was not applied. This may be an experimental error, or the cathode additive contained in the lithium secondary battery may not only suppress gas generation but also absorb the generated gas. It is expected that there is a possibility.

Although the present invention has been described above with limited examples and drawings, the present invention is not limited thereto, and the technical idea of the present invention and the following description will be provided by those skilled in the art in the technical field to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalence of the patent claims.

Claims (15)

Lithium transition metal oxide represented by Formula 1:
[Formula 1]
Li ₆ Co _1-xy Zn _x M _y O ₄
In Formula 1,
M is a group 2 element, a group 13 element, a group 14 element, a 5-period transition metal, or a 6-period transition metal,
x is 0.1 to 0.7,
y is 0.01 to 0.2.
delete delete delete delete delete According to claim 1,
The lithium transition metal oxide wherein M is at least one selected from the group consisting of Al, Mg, Ti, Zr, Nb, and W.
According to claim 1,
The lithium transition metal oxide is Li ₆ Co _0.77 Zn _0.2 Al _0.03 O ₄ , Li ₆ Co _0.76 Zn _0.2 Al _0.04 O ₄ , Li ₆ Co _0.75 Zn _0.2 Al _0.05 O ₄ , Li ₆ Co _0.7 Zn _0.25 Al _0.05 O ₄ , Li ₆ Co _0.65 Zn _0.25 Al _0.1 O ₄ , Li ₆ Co _0.67 Zn _0.3 Al _0.03 O ₄ , Li ₆ Co _0.66 Zn _0.3 Al _0.04 O ₄ , Li ₆ Co _0.65 Zn _0.3 Al _0.05 O ₄ , Li ₆ Co _0.6 Zn _0.3 Al _0.1 O ₄ , Li ₆ Co _0.77 Zn _0.2 Mg _0.03 O ₄ , Li ₆ Co _0.76 Zn _0.2 Mg _0.04 O ₄ , Li ₆ Co _0.75 Zn _0.2 Mg _0.05 O ₄ , Li ₆ Co _0.7 Zn _0.25 Mg _0.05 O ₄ , Li _{6 CO 0.67 Zn 0.3 mg 0.03} o _{4 , Li 66 Zn 0.3 mg 0.04} O ₄ , _{Li 6} CO _0.65 Zn _0.3 mg _{0.05 o 4 0.04} O ₄ , Li ₆ Co _0.75 Zn _0.2 Ti _0.05 O ₄ , Li ₆ Co _0.72 Zn _0.25 Ti _0.03 O ₄ , Li ₆ Co _0.67 Zn _0.3 Ti _0.03 O ₄ , Li ₆ Co _0.66 Zn _0.3 Ti _0.04 O ₄ , Li ₆ Co _0.65 Zn _0.3 Ti _0.05 O ₄ , Li ₆ Co _{0.77 Zn 0.2} Zr _0.03 O ₄ , Li ₆ Co _0.76 Zn _0.2 Zr _0.04 O ₄ , Li ₆ Co _0.75 Zn _0.2 Zr 0.05 O ₄ , Li ₆ Co _0.72 Zn _0.25 Zr _0.03 O ₄ , Li ₆ Co _0.67 Zn _0.3 Zr _0.03 O ₄ , Li ₆ Co _0.66 Zn _0.3 Zr _0.04 O ₄ , Li ₆ Co _0.65 Zn _0.3 Zr _0.05 O ₄ , Li ₆ Co _0.77 Zn _0.2 Nb _0.03 O ₄ , Li ₆ Co _0.76 Zn _0.2 Nb _0.04 O ₄ , Li ₆ Co _0.75 Zn _0.2 Nb _0.05 O ₄ , Li ₆ Co _0.67 Zn _0.3 Nb _0.03 O ₄ , Li ₆ Co _0.66 Zn _0.3 Nb _0.04 O ₄ , Li ₆ Co _0.65 Zn _0.3 Nb _0.05 O ₄ , Li ₆ Co _0.77 Zn _0.2 W _0.03 O ₄ , Li ₆ Co _0.76 Zn _0.2 W _0.04 O ₄ , Li ₆ Co _0.75 Zn _0.2 W _0.05 O ₄ , Li ₆ Co _0.67 Zn _0.3 W _0.03 O ₄ , Li ₆ Co _0.66 Lithium transition metal oxide comprising at least one compound selected from the group consisting of Zn _0.3 W _0.04 O ₄ , and Li ₆ Co _0.65 Zn _0.3 W _0.05 O ₄ .
A first step of solid-phase mixing of lithium oxide, cobalt oxide, and heteroelement oxide; and
A second step of obtaining the lithium transition metal oxide according to claim 1 by calcining the mixture obtained in the first step in an inert atmosphere and at a temperature of 550 °C to 750 °C,
The heterogeneous element oxide includes zinc oxide; and oxides of Group 2 elements, Group 13 elements, Group 14 elements, 5-period transition metals, or 6-period transition metals.
Method for producing lithium transition metal oxide.
According to clause 9,
In the second step, the mixture obtained in the first step is heated at a temperature increase rate of 1.4 °C/min to 2.0 °C/min under an inert atmosphere and heated at a temperature of 550 °C to 750 °C for 2 to 20 hours. A method for producing lithium transition metal oxide, performing calcination.
A positive electrode additive for a lithium secondary battery comprising the lithium transition metal oxide according to claim 1.
A positive electrode for a lithium secondary battery comprising a positive electrode active material, a binder, a conductive material, and the lithium transition metal oxide according to claim 1.
A positive electrode for a lithium secondary battery, comprising a positive electrode active material, a binder, a conductive material, and a positive electrode additive for a lithium secondary battery according to claim 11.
A positive electrode for a lithium secondary battery according to claim 12 or 13; cathode; separation membrane; And a lithium secondary battery comprising an electrolyte.
According to claim 14,
A lithium secondary battery, wherein the negative electrode includes at least one negative electrode active material selected from the group consisting of carbonaceous materials and silicon compounds.