KR20190108842A - Positive electrode for lithium secondary battery, preparing method thereof, and lithium secondary battery comprising the same - Google Patents

Abstract

A positive electrode for a secondary battery is provided, which comprises: a positive electrode current collector; a positive electrode active material layer disposed on at least one surface of the positive electrode current collector and including a lithium transition metal oxide represented by chemical formula 1; and an inorganic material layer disposed on the positive electrode active material layer. The inorganic layer comprises an inorganic material which is an oxide or hydroxide of at least one metal selected from a group consisting of Mg, Al, and Zn. The chemical formula 1 is represented by: Li_xNi_yM_1-yO_2-zA_z. In the chemical formula 1, the definitions for x, y, z, M and A refer to the detailed description of the invention.

Description

Positive electrode for lithium secondary battery, manufacturing method thereof and lithium secondary battery including same {Positive electrode for lithium secondary battery, preparing method etc, and lithium secondary battery comprising the same}

It relates to a positive electrode for a lithium secondary battery, a manufacturing method thereof, and a lithium secondary battery including the same.

Lithium secondary batteries are used as power sources for portable electronic devices such as video cameras, mobile phones, and notebook computers. Rechargeable lithium secondary batteries are more than three times higher in energy density per unit weight and can be charged faster than conventional lead acid batteries, nickel-cadmium batteries, nickel hydrogen batteries and nickel zinc batteries.

Lithium secondary batteries are powered by oxidation and reduction reactions when lithium ions are inserted / desorbed from the positive electrode and the negative electrode while an organic or polymer electrolyte is charged between the positive electrode and the negative electrode including an active material capable of inserting and removing lithium ions. To produce energy.

As the cathode active material included in the cathode of the lithium secondary battery, a lithium-containing metal oxide is commonly used. For example, as a positive electrode active material of a lithium secondary battery, transition metal oxides such as lithium cobalt oxide (LiCoO ₂ ), lithium manganese oxide (LiMn ₂ O ₄ ) or lithium nickel oxide (LiNiO ₂ ), and a part of these transition metals Composite oxides substituted with other transition metals are used.

In the case of the Ni-containing positive electrode active material containing much Ni, many studies have been recently conducted in that a battery having high capacity, excellent rate characteristics, and low cost can be realized as compared with conventional lithium cobalt oxide.

However, in the case of a high Ni-containing positive electrode active material, the surface structure of the positive electrode is weak, and the surface of the positive electrode contains a large amount of residual lithium such as lithium hydroxide, lithium carbonate, etc., so that its long-term use rapidly decreases its life characteristics. There are problems such as swelling due to gas generation, low chemical stability, and the like.

Accordingly, there is a demand for a lithium secondary battery employing a positive electrode including a high Ni-containing positive electrode active material, and exhibiting high capacity but excellent cycle characteristics and high stability.

One aspect of the present invention is to provide a positive electrode for a secondary battery having a novel composition including a high Ni-containing positive electrode active material, a layer containing an inorganic material.

Another aspect of the present invention is to provide a method for manufacturing the secondary battery positive electrode.

Another aspect of the present invention is to provide a lithium secondary battery employing the positive electrode for the secondary battery.

In one aspect of the invention, a positive electrode current collector;

A cathode active material layer disposed on at least one surface of the cathode current collector and including a lithium transition metal oxide represented by Formula 1 below; And

Including an inorganic material layer disposed on the positive electrode active material layer,

The inorganic layer is provided with a positive electrode for a secondary battery comprising an inorganic material which is an oxide or hydroxide of at least one metal selected from the group consisting of Mg, Al, and Zn:

<Formula 1>

Li _x Ni _y M _1-y O _2-z A _z

Where

0.9 ≦ x ≦ 1.2, 0.7 ≦ y ≦ 0.98, 0 ≦ z <0.2,

M is at least one oxidation or water +2 or + trivalent metal or transition metal element;

A is at least one oxidation number -1 or -divalent element.

In another aspect, applying a first composition comprising a lithium transition metal oxide represented by the following formula (1) on at least one surface of the positive electrode current collector and dried to form a positive electrode active material layer; And

Applying a second composition including an inorganic material which is an oxide or a hydroxide of at least one metal selected from the group consisting of Mg, Al, and Zn on the cathode active material layer, and then drying to form an inorganic material layer; A method of making a battery positive electrode is provided:

<Formula 1>

Li _x Ni _y M _1-y O _2-z A _z

Where

0.9 ≦ x ≦ 1.2, 0.7 ≦ y ≦ 0.98, 0 ≦ z <0.2,

M is at least one oxidation or water +2 or + trivalent metal or transition metal element;

A is at least one oxidation number -1 or -divalent element.

In another aspect, the secondary battery positive electrode;

A cathode disposed opposite the anode; And

There is provided a lithium secondary battery comprising a; electrolyte disposed between the positive electrode and the negative electrode.

Lithium secondary battery according to one embodiment by using a positive electrode including a layer structure of a novel configuration, the life characteristics are improved, the amount of gas generated during high temperature storage is reduced, the high temperature stability is improved, the high temperature storage characteristics can be improved have.

1 is a schematic diagram of a lithium secondary battery according to an exemplary embodiment.
2 is a schematic diagram of a positive electrode for a secondary battery according to an exemplary embodiment.
3 is a schematic diagram illustrating a method of manufacturing a cathode for a secondary battery according to an exemplary embodiment.
4 is a graph showing the amount of gas generated during high temperature storage of the lithium secondary battery to which the cathodes prepared in Examples 1 to 2 and Comparative Example 1 are applied.
5 is a graph showing the high-temperature storage characteristics of the lithium secondary battery to which the cathodes prepared in Examples 1 to 4 and Comparative Example 1 are applied.
<Explanation of symbols for main parts of the drawings>
1: lithium secondary battery 2: negative electrode
3: anode 4: separator
5: battery case 6: cap assembly
10: positive electrode for secondary battery 11: positive electrode current collector
12: positive electrode active material layer 13: inorganic material layer

Hereinafter, the present invention will be described in more detail.

Hereinafter, a positive electrode for a secondary battery according to an embodiment of the present invention will be described with reference to FIG. 2. 2 is a schematic diagram of a positive electrode for a secondary battery according to an exemplary embodiment. Referring to FIG. 2, the secondary battery positive electrode 10 according to one side includes a positive electrode current collector 11; A cathode active material layer 12 disposed on at least one surface of the cathode current collector 11 and including a lithium transition metal oxide; And an inorganic layer 13 disposed on the cathode active material layer 12.

The inorganic layer 13 includes an oxide or hydroxide of at least one metal selected from the group consisting of Mg, Al, and Zn,

At this time, the inorganic material, for example, is preferably capable of bonding with anions (eg, F ⁻ ions) generated by the electrolyte decomposition reaction in the battery, when combined with the anion, by-products (HF, etc.) content in the electrolyte As a result, it is possible to more effectively reduce the anode surface side reactions caused by the by-products.

In one specific example, the inorganic material may have a specific surface area of 10 m ² / g or less. For example, the inorganic material may have a specific surface area of 3 m ² / g to 10 m ² / g. For example, the inorganic material may have a specific surface area of 3 m ² / g to 8 m ² / g. If the specific surface area of the inorganic material exceeds 10 m ² / g out of the above range, there is a problem in that the adhesion of the inorganic material layer to the positive electrode active material layer is inferior.

The inorganic material may be included in an amount of 80 to 98 parts by weight based on the inorganic material layer. Specifically, it may be included in 90 to 98 parts by weight. When included in the above range, it is advantageous to exhibit the effects of the present invention, such as suppressing side reactions with the electrolyte and improving life characteristics.

In one specific example, the inorganic material may be an oxide or hydroxide of Mg, Al, or Zn, but is not limited thereto.

As described above, when the inorganic material is an oxide or hydroxide of Mg, Al, or Zn, the content of moisture adsorbed to the inorganic material is reduced, so that the amount of gas generated at high temperature storage can be significantly reduced. In one specific example, the inorganic material may be at least one selected from Mg (OH) ₂ , AlO (OH), Al (OH) ₃ and ZnO.

In one specific example, the thickness ratio of the positive electrode active material layer 12 to the inorganic material layer 13 may be 2: 1 to 4: 1. In one embodiment, the positive electrode active material layer may have a thickness of 6 μm to 40 μm. In another embodiment, the thickness of the inorganic layer may be 3 ㎛ to 15 ㎛, more specifically 3 ㎛ to 10 ㎛. Out of the range, the thickness ratio of the positive electrode active material layer to the inorganic material layer is less than 2: 1, the thickness of the positive electrode active material layer is less than 6 ㎛, or the thickness of the inorganic material layer exceeds 10 ㎛, compared to the positive electrode active material layer If the inorganic layer is too thick, there is a problem that the capacity of the lithium secondary battery relative to the volume is too low. On the other hand, when the thickness ratio of the positive electrode active material layer to the inorganic material layer is greater than 4: 1, the thickness of the positive electrode active material layer is greater than 40 μm, or the thickness of the inorganic material layer is less than 3 μm, the positive electrode active material layer is an inorganic material layer When too thick, it has the effect of increasing the capacity of the lithium secondary battery, but it does not sufficiently prevent side reactions occurring on the surface of the positive electrode, resulting in deterioration of the life characteristics, especially high temperature characteristics such as high temperature life characteristics and high temperature stability This can be degraded.

The cathode active material layer 12 may include a lithium transition metal oxide represented by the following Chemical Formula 1.

<Formula 1>

Li _x Ni _y M _1-y O _2-z A _z

Where

0.9 ≦ x ≦ 1.2, 0.7 ≦ y ≦ 0.98, 0 ≦ z <0.2,

M is at least one oxidation or water +2 or + trivalent metal or transition metal element;

A is at least one oxidation number -1 or -divalent element.

In the case of using a lithium transition metal oxide having a high Ni content as the positive electrode active material having a mole fraction of Ni of 0.7 or more in the transition metal as shown in Chemical Formula 1, despite the advantage that a high capacity battery can be realized, long-life characteristics or high temperature stability And there is a disadvantage that the deterioration of the high temperature storage characteristics is severe, due to these disadvantages there is a difficulty in commercialization. Accordingly, the lithium secondary battery may exhibit excellent life characteristics and high temperature stability by a mechanism such as preventing side reactions occurring on the surface of the cathode by forming the inorganic material layer on the cathode active material layer as a configuration for solving the problem. Can be.

For example, A in Formula 1 may be one of halogen, S, and N, but is not limited thereto. For example, in Formula 1, M is Al, Mg, Mn, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W and Bi It may be one or more elements selected from the group consisting of.

For example, in Formula 1, y represents the content of Ni in the lithium transition metal oxide, and may be 0.7 ≦ y ≦ 0.98. For example, in Formula 1, 0.8 ≦ y ≦ 0.98. For example, in Formula 1, 0.8 ≦ y ≦ 0.9. For example, in Formula 1, 0.8 ≦ y ≦ 0.88.

For example, the lithium transition metal oxide may be represented by the following Chemical Formula 2 or Chemical Formula 3:

<Formula 2>

LiNi _{y '} Co _1-y'-z' Al _{z '} O ₂

<Formula 3>

LiNi _{y '} Co _1-y'-z' Mn _{z '} O ₂

In Formulas 2 and 3, 0.9 ≦ x '≦ 1.2, 0.8 ≦ y' ≦ 0.98, 0 <z '<0.1, and 0 <1-y'-z' <0.2.

For example, the positive electrode for the secondary battery is LiNi _0.8 Co _0.15 Mn _0.05 O ₂ , LiNi _0.85 Co _0.1 Mn _0.05 O ₂ , LiNi _0.88 Co _0.08 Mn _0.04 O ₂ , LiNi _0.88 Co _0.08 Al _0.04 O ₂ , Li _1.02 Ni _0.80 Co _0.15 Mn _0.05 O ₂ , Li _1.02 Ni _0.85 Co _0.10 Mn _0.05 O ₂ , Li _1.02 Ni _0.88 Co _0.08 Mn _0.04 O ₂ , Li _1.02 Ni _0.88 Co _0.08 Al _0.04 O ₂ , LiNi _0.8 Co _0.15 Al _0.05 O ₂ , LiNi _0.88 Co _0.1 Al _0.02 O ₂ , LiNi _0.88 Co _0.12 Mn _0.04 O ₂ , LiNi _0.85 Co _0.1 Al _0.05 O ₂ , LiNi _0.88 Co _0.1 Mn _0.02 O ₂ and at least one lithium transition metal oxide may be included as a positive electrode active material.

Hereinafter, a method of manufacturing a cathode for a secondary battery according to an embodiment of the present invention will be described with reference to FIG. 3. 3 is a schematic diagram illustrating a method of manufacturing a cathode for a secondary battery according to an exemplary embodiment. Referring to FIG. 3, a method of manufacturing a secondary battery positive electrode 10 according to another aspect of the present invention may include: a first method including a lithium transition metal oxide represented by Chemical Formula 1 on at least one surface of a positive electrode current collector 11; Applying the composition to form a positive electrode active material layer 12; And applying a second composition including an oxide or a hydroxide of at least one metal selected from the group consisting of Mg, Al, and Zn on the cathode active material layer 12 to form an inorganic layer 13. do:

<Formula 1>

Li _x Ni _y M _1-y O _2-z A _z

Where

0.9 ≦ x ≦ 1.2, 0.7 ≦ y ≦ 0.98, 0 ≦ z <0.2,

M is at least one oxidation or water +2 or + trivalent metal or transition metal element;

A is at least one oxidation number -1 or -divalent element.

In one specific example, the first composition or the second composition may further include a binder and a conductive material.

The binder is a lithium transition metal oxide, i.e., a component that assists the bonding between the positive electrode active material or the inorganic material and the conductive material, and the current collector, and is formed between the positive electrode current collector and the positive electrode active material layer, in the positive electrode active material layer, and the positive electrode active material. It may be included between the layer and the inorganic layer, or in the inorganic layer, and may be added in an amount of 1 to 50 parts by weight based on 100 parts by weight of the positive electrode active material or the inorganic material. For example, the binder may be added in the range of 1 to 30 parts by weight, 1 to 20 parts by weight, or 1 to 15 parts by weight based on 100 parts by weight of the positive electrode active material or the inorganic material. For example, the binder may be polyvinylidene fluoride, polyvinylidene chloride, polybenzimidazole, polyimide, polyvinylacetate, polyacrylonitrile, polyvinyl alcohol, carboxymethylcellulose (CMC), starch. , Hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polyaniline, acrylonitrile butadiene styrene, phenol resin, epoxy resin , Polyethylene terephthalate, polytetrafluoroethylene, polyphenylene sulfide, polyamideimide, polyetherimide, polyethersulfone, polyamide, polyacetal, polyphenylene oxide, polybutylene terephthalate, ethylene-propylene-diene Consisting of terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR) and fluorine rubber It may be one or more selected from the group. For example, when two or more binders of the above examples are used, the various copolymers in which the two or more binders are polymerized may be a binder.

The first composition or the second composition may optionally further include a conductive material to provide a conductive passage to the above-described positive electrode active material or inorganic material to further improve electrical conductivity. As the conductive material, any one generally used in a lithium secondary battery may be used, and examples thereof include carbon-based materials such as carbon black, acetylene black, ketjen black, and carbon fibers (eg, vapor-grown carbon fibers); Metal materials such as metal powder or metal fibers such as copper, nickel, aluminum and silver; Conductive materials containing conductive polymers such as polyphenylene derivatives or mixtures thereof can be used. The content of the conductive material can be appropriately adjusted. For example, the weight ratio of the positive electrode active material or the inorganic material and the conductive material may be added in a range of 99: 1 to 90:10.

The positive electrode current collector has a thickness of 3 μm to 500 μm and is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon Or a surface treated with carbon, nickel, titanium, silver, or the like on the surface of aluminum or stainless steel can be used. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and may be in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The prepared first composition may be directly applied onto a positive electrode current collector and dried to prepare a positive electrode plate. Alternatively, the first composition may be cast on a separate support, and then a film obtained by peeling from the support may be laminated on a cathode current collector to prepare a cathode electrode plate.

On the other hand, the first composition or the second composition may further include a solvent.

N-methylpyrrolidone, acetone or water may be used as the solvent, but is not limited thereto, and any solvent may be used as long as it can be used in the art.

In one specific example, the content of the lithium transition metal oxide may be 80 to 98% by weight based on the total weight of the first composition. For example, the content of the lithium transition metal oxide may be 85 to 98 wt% based on the total weight of the first composition, but is not limited thereto.

In one specific example, the content of the inorganic material may be 80 to 98% by weight based on the total weight of the second composition. For example, the inorganic content may be 85 to 98 wt% based on the total weight of the second composition, but is not limited thereto.

For example, after applying the first composition or the second composition, when drying, the drying may be carried out by primary drying for about 5 to 30 minutes in the temperature range of 80 to 130 ℃.

In another aspect of the invention, the lithium secondary battery is a secondary battery positive electrode as described above; A cathode disposed opposite the anode; And an electrolyte disposed between the positive electrode and the negative electrode.

The secondary battery positive electrode essentially includes the positive electrode current collector, the positive electrode active material layer, and the inorganic material layer, and the description thereof will be referred to the above. Furthermore, the positive electrode active material layer may include the above-described lithium transition metal oxide as an essential component, and may further include a positive electrode active material commonly used in a lithium secondary battery in addition to the essential component.

For example, Li _a A ' _1-b B _b D ₂ (wherein 0.90 ≦ a ≦ 1 and 0 ≦ b ≦ 0.5); Li _a E _1-b B _b 0 _2-c D _c (wherein 0.90 ≦ a ≦ 1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); LiE _2-b B _b 0 _4-c D _c (wherein 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); Li _a Ni _1-bc Co _b B _c D _α (wherein 0.90 ≦ a ≦ 1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α ≦ 2); Li _a Ni _1-bc Co _b B _c 0 _2-α F _α (wherein 0.90 ≦ a ≦ 1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2); Li _a Ni _1-bc Co _b B _c O _2-α F ₂ (wherein 0.90 ≦ a ≦ 1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2); Li _a Ni _1-bc Mn _b B _c D _α (wherein 0.90 ≦ a ≦ 1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α ≦ 2); Li _a Ni _1-bc Mn _b B _c O _2-α F _α (wherein 0.90 ≦ a ≦ 1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2); Li _a Ni _1-bc Mn _b B _c O _2-α F ₂ (wherein 0.90 ≦ a ≦ 1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α <2); Li _a Ni _b E _c G _d O ₂ (wherein 0.90 ≦ a ≦ 1, 0 ≦ b ≦ 0.9, 0 ≦ c ≦ 0.5, and 0.001 ≦ d ≦ 0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (wherein 0.90 ≦ a ≦ 1, 0 ≦ b ≦ 0.9, 0 ≦ c ≦ 0.5, 0 ≦ d ≦ 0.5, and 0.001 ≦ e ≦ 0.1); Li _a NiG _b O ₂ (wherein 0.90 ≦ a ≦ 1, 0.001 ≦ b ≦ 0.1); Li _a CoG _b O ₂ (wherein 0.90 ≦ a ≦ 1, 0.001 ≦ b ≦ 0.1); Li _a MnG _b O ₂ (wherein 0.90 ≦ a ≦ 1, 0.001 ≦ b ≦ 0.1); Li _a Mn ₂ G _b O ₄ (wherein 0.90 ≦ a ≦ 1, 0.001 ≦ b ≦ 0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiIO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≦ f ≦ 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0 ≦ f ≦ 2); It may further comprise a compound represented by any one of the formula of LiFePO ₄ :

In the above formula, A 'is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or combinations thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. For example, LiCoO ₂ , LiMn _{x ''} O _{2x ''} (x '' = 1, 2), LiNi _{1-x ''} Mn _{x ''} O _{2x ''} (0 <x ''<1), LiNi _{1-x ''-y ''} Co _{x ''} Mn _{y ''} O ₂ (0≤x''≤0.5, 0≤y''≤0.5), FePO ₄ and the like.

On the other hand, the negative electrode may be manufactured by the following method.

For example, a negative electrode active material composition is prepared by mixing a negative electrode active material, a conductive material, a binder, and a solvent. The negative electrode active material composition is directly coated and dried on a metal current collector to prepare a negative electrode plate. Alternatively, the negative electrode active material composition may be cast on a separate support, and then a film peeled from the support may be laminated on a metal current collector to prepare a negative electrode plate.

The negative electrode active material may be any one that can be used as a negative electrode active material of a lithium battery in the art. For example, it may include one or more selected from the group consisting of lithium metal, a metal alloyable with lithium, a transition metal oxide, a non-transition metal oxide, and a carbon-based material.

For example, the metal alloyable with lithium is Si, Sn, Al, Ge, Pb, Bi, Sb Si-Y alloy (The Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth Element or a combination thereof, not Si), Sn-Y alloy (Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element or combination thereof, and not Sn. ) And the like. As the element Y, 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, Ti, Ge, P, As, Sb, Bi, S, Se, or Te. For example, the transition metal oxide may be lithium titanium oxide, vanadium oxide, lithium vanadium oxide, or the like. For example, the non-transition metal oxide may be SnO ₂ , SiO _{x ′ ″} (0 <x ′ ″ <2), or the like.

The carbonaceous material may be crystalline carbon, amorphous carbon or a mixture thereof. The crystalline carbon may be graphite such as amorphous, plate-like, flake, spherical or fibrous natural graphite or artificial graphite, and the amorphous carbon may be soft carbon (low temperature calcined carbon) or hard carbon (hard). carbon, mesophase pitch carbide, calcined coke, and the like.

In the negative electrode active material composition, the same conductive material, binder, and solvent as in the case of the positive electrode active material composition (ie, the first composition) may be used.

The amount of the negative electrode active material, the conductive material, the binder, and the solvent is at a level commonly used in lithium batteries. At least one of the conductive material, the binder, and the solvent may be omitted according to the use and configuration of the lithium battery.

Next, a separator to be inserted between the positive electrode and the negative electrode is prepared.

The separator may be used as long as it is commonly used in lithium batteries. A low resistance to the ion migration of the electrolyte and excellent in the ability to hydrate the electrolyte can be used. For example, it is selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be in a nonwoven or woven form. For example, a rollable separator such as polyethylene or polypropylene may be used for a lithium ion battery, and a separator having excellent organic electrolyte solution impregnation ability may be used for a lithium ion polymer battery. For example, the separator may be manufactured according to the following method.

A separator composition is prepared by mixing a polymer resin, a filler, and a solvent. The separator composition may be directly coated and dried on the electrode to form a separator. Alternatively, after the separator composition is cast and dried on a support, a separator film separated from the support may be laminated on the electrode to form a separator.

The polymer resin used to manufacture the separator is not particularly limited, and any materials used for the binder of the electrode plate may be used. For example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate or mixtures thereof and the like can be used.

Next, the electrolyte is prepared.

For example, the electrolyte may be an organic electrolyte. In addition, the electrolyte may be a solid. For example, it may be boron oxide, lithium oxynitride, and the like, but is not limited thereto, and any one that can be used as a solid electrolyte in the art may be used. The solid electrolyte may be formed on the negative electrode by sputtering or the like.

For example, the organic electrolyte may be prepared by dissolving lithium salt in an organic solvent.

The organic solvent may be used as long as it can be used as an organic solvent in the art. For example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate , Benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N, N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide , Dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether or a mixture thereof.

Any lithium salt may be used as long as it can be used as a lithium salt in the art. For example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiAlO ₂ , LiAlCl ₄ , LiN (C _{x ''''} F _{2x '''' + 1} SO ₂ ) (C _{y ''''} F _{2y '''' + 1} SO ₂ ) (where x '''', y '''' is a natural number) , LiCl, LiI or a mixture thereof.

As shown in FIG. 1, the lithium secondary battery 1 includes a positive electrode 3, a negative electrode 2, and a separator 4. The positive electrode 3, the negative electrode 2, and the separator 4 described above are wound or folded to be accommodated in the battery case 5. Subsequently, the organic electrolyte is injected into the battery case 5 and sealed with a cap assembly 6 to complete the lithium secondary battery 1. The battery case 5 may be cylindrical, rectangular, thin film, or the like. For example, the lithium secondary battery 1 may be a thin film type battery. The lithium secondary battery 1 may be a lithium ion battery.

A separator may be disposed between the positive electrode and the negative electrode to form a battery structure. The battery structure is stacked in a bi-cell structure, and then impregnated in an organic electrolyte, and the resultant is accommodated in a pouch and sealed to complete a lithium ion polymer battery.

The lithium secondary battery may not only be used in a battery used as a power source for a small device, but may also be used as a unit cell of a medium-large device battery module including a plurality of batteries.

Examples of such medium and large devices include a power tool; XEVs including Electric Vehicles (EVs), Hybrid Electric Vehicles (HEVs), and Plug-in Hybrid Electric Vehicles (PHEVs); Electric two-wheeled vehicles including E-bikes and E-scooters; Electric golf carts; Electric trucks; Electric commercial vehicles; Or a system for storing power; Although these etc. are mentioned, It is not limited to these. In addition, the lithium secondary battery may be used for all other applications requiring high power, high voltage, and high temperature driving.

Exemplary embodiments are described in more detail through the following examples and comparative examples. However, the embodiments are provided to illustrate the technical idea, and the scope of the present invention is not limited only to these examples.

(Manufacture of Anode)

Example 1

A first composition was prepared by mixing LiNi _0.8 Mn _0.1 Co _0.1 O ₂ 96 wt% as the cathode active material, super-p 2 wt% as the conductive material, and 2 wt% polyvinylidene fluoride as the binder. The first composition was applied to an aluminum (Al) thin film, which is a positive electrode current collector having a thickness of about 20 μm, dried at about 80 ° C. for 20 minutes, and then subjected to roll press to obtain a positive electrode active material layer.

On the positive electrode active material layer, a second composition obtained by mixing 95% by weight of ZnO (specific surface area: 3.3 g / m ² ) with 5% by weight of polyvinylidene fluoride with a binder was applied to form an inorganic material layer. Then, drying was performed at about 80 ° C. for 20 minutes to prepare a double coated anode. At this time, the thickness of the positive electrode active material layer was about 30㎛, the thickness of the inorganic material layer was about 10㎛, the thickness ratio of the positive electrode active material layer and the inorganic material layer was about 3: 1.

Example 2

A positive electrode was prepared in the same manner as in Example 1, except that Mg (OH) ₂ (specific surface area: 7.2 g / m ² ) was used as the inorganic material.

Example 3

A positive electrode was manufactured in the same manner as in Example 1, except that AlO (OH) (specific surface area: 3.6 g / m ² ) was used as the inorganic material.

Example 4

A positive electrode was prepared in the same manner as in Example 1, except that Al (OH) ₃ (specific surface area: 5.3 g / m ² ) was used as the inorganic material.

Comparative Example 1

A positive electrode was prepared in the same manner as in Example 1 except that the inorganic layer was not formed on the cathode active material layer in Example 1.

Comparative Example 2

90 wt% LiNi _0.8 Mn _0.1 Co _0.1 O ₂ as the positive electrode active material, 6 wt% ZnO (specific surface area: 3.3 g / m ² ) as the inorganic material, 2 wt% super-p as the conductive material, and polyvinylidene fluoride 2 as the binder The positive electrode composition was prepared by mixing the wt%. The positive electrode composition was applied to a thin film of aluminum (Al), which is a positive electrode current collector having a thickness of about 20 μm, dried at about 80 ° C. for 20 minutes, and then subjected to roll press to prepare a positive electrode. At this time, the thickness of the cathode active material layer was about 30 μm.

Comparative Example 3

A positive electrode was manufactured in the same manner as in Example 1, except that ZrO ₂ was used as the inorganic material.

Evaluation Example 1 Evaluation of Electrochemical Properties

A mixed solvent (EC: EMC: DMC) of the positive electrode prepared in Examples 1 to 4 and Comparative Examples 1 to 3, and ethylene carbonate (EC), ethylene methylene carbonate (EMC) and dimethyl carbonate (DMC) is 2: 4: LiPF ₆ is using the electrolyte dissolved to a concentration of 1.15M, was prepared in the half-cell in a volume ratio of 4).

For each half cell, the electrochemical properties (e.g. rate-specific capacity, high rate characteristics, room temperature life after 50 cycles, high temperature (45 ° C) life after 50 cycles) at operating voltages of 2.5 to 4.35 V are measured, The results are shown in Table 1 below.

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 0.1C Charge capacity (mAh) 6.27 6.28 6.35 6.30 6.18 6.21 6.32 Discharge Capacity (mAh) 5.72 5.73 5.79 5.75 5.64 5.57 5.64 Initial Efficiency (%) 91.2 91.2 91.2 91.1 91.3 89.7 89.2 Rate capacity
(mAh) 0.1C 5.72 5.73 5.79 5.75 5.64 5.57 5.64 0.2C 5.56 5.57 5.63 5.59 5.49 5.32 5.37 0.33C 5.43 5.44 5.50 5.46 5.38 5.23 5.30 0.5C 5.32 5.33 5.39 5.35 5.27 5.04 5.12 1.0C 5.17 5.18 5.24 5.20 5.11 4.88 4.95 2.0C 4.97 5.00 5.05 5.00 4.88 4.68 4.73 High rate characteristic (%) 1.0C / 0.2C 93.0 93.1 93.0 93.1 93.1 91.7 92.2 2.0C / 0.2C 89.4 89.8 89.7 89.6 88.9 88.0 88.1 Room temperature life (%) 4.35V 90.6 90.1 89.2 89.8 76.6 82.9 81.1 High temperature life (%) 4.35V 81.9 81.7 78.0 79.6 67.8 73.2 71.5

Referring to Table 1, the half cell using the positive electrode according to Examples 1 to 4 including the inorganic layer, as well as the half cell using the positive electrode according to Comparative Examples 2 and 3 containing the same inorganic material, it does not contain an inorganic material Compared with the half cell using the positive electrode according to Comparative Example 1 which does not, there is no reduction in capacity and high rate characteristics. In particular, compared with Comparative Examples 2 and 3 containing an inorganic substance, the half battery using the positive electrodes according to Examples 1 to 4 exhibits excellent high rate characteristics. In addition, compared to the half-cell using the positive electrode according to the comparative example can exhibit a significantly superior level of room temperature / high temperature life characteristics. That is, it can be seen that the battery including the positive electrode of the present invention exhibits excellent life characteristics while maintaining the battery capacity at an appropriate level.

Evaluation Example 2: High Temperature Stability Evaluation

A mixed solvent (EC: EMC: DMC) of the positive electrode prepared in Examples 1 to 2 and Comparative Example 1, and ethylene carbonate (EC), ethylene methylene carbonate (EMC) and dimethyl carbonate (DMC) is 2: 4: 4. A half cell was prepared using an electrolyte in which LiPF ₆ was dissolved in a volume ratio of 1.15 M).

Each half cell was stored at high temperature (80 ° C.) and the amount of gas generated over time was measured, and the results are shown in FIG. 4.

Referring to FIG. 4, the half cell using the positive electrodes according to Examples 1 to 2 generated a much lower amount of gas during high temperature storage than the half cell using the positive electrode according to Comparative Example 1.

That is, when using the anode including the inorganic layer according to the present invention, the amount of gas generated during high temperature storage is suppressed, it can be seen that exhibits an excellent level of high temperature stability.

Evaluation Example 3: Measurement of High Temperature Storage Characteristics

A mixed solvent (EC: EMC: DMC) of the positive electrode prepared in Examples 1 to 4 and Comparative Example 1, and ethylene carbonate (EC), ethylene methylene carbonate (EMC) and dimethyl carbonate (DMC) is 2: 4: 4. A coin cell was prepared using an electrolyte in which LiPF ₆ was dissolved at a concentration of 1.15 M and a lithium metal as a negative electrode in a volume ratio).

Each half cell was stored at SOC at 100% (full charge) for 7 days at high temperature (60 ° C.), and then the charge transfer resistance (Rct) before and after storage was measured, and the results are shown in FIG. 5. Shown. In this case, the lower the Rct value, the better the high temperature storage characteristics.

Referring to FIG. 5, the Rct values before the high temperature storage of the coin cells using the anodes prepared in Examples 1 to 4 and Comparative Example 1 were almost similar. However, the Rct values after the high temperature storage were performed in Examples 1 to 4, respectively. Coin cell using the prepared positive electrode was significantly lower.

That is, in the case of using the anode including the inorganic layer according to the present invention, it is possible to suppress the increase in the Rct value during high temperature storage, and thus it can be confirmed that the high level of high temperature storage characteristics are exhibited.

In the above described a preferred embodiment according to the present invention with reference to the drawings and embodiments, but this is only exemplary, those skilled in the art that various modifications and equivalent other embodiments are possible from this. You will understand. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims (10)

A positive electrode current collector;
A cathode active material layer disposed on at least one surface of the cathode current collector and including a lithium transition metal oxide represented by Formula 1 below; And
Including an inorganic material layer disposed on the positive electrode active material layer,
The inorganic layer positive electrode for a secondary battery comprising an inorganic material which is an oxide or hydroxide of one or more metals selected from the group consisting of Mg, Al, and Zn:
<Formula 1>
Li _x Ni _y M _1-y O _2-z A _z
Where
0.9 ≦ x ≦ 1.2, 0.7 ≦ y ≦ 0.98, 0 ≦ z <0.2,
M is at least one oxidation or water +2 or + trivalent metal or transition metal element;
A is at least one oxidation number -1 or -divalent element. The method of claim 1,
The inorganic material has a specific surface area of 10 m ² / g or less, the positive electrode for a secondary battery. The method of claim 1,
The inorganic material is one or more selected from Mg (OH) ₂ , AlO (OH), Al (OH) ₃ and ZnO, the positive electrode for secondary batteries. The method of claim 1,
The thickness ratio of the positive electrode active material layer to the inorganic material layer is 2: 1 to 4: 1, the secondary battery positive electrode. The method of claim 1,
The positive electrode active material layer has a thickness of 6 μm to 40 μm. The method of claim 1,
The inorganic layer has a thickness of 3 μm to 10 μm. The method of claim 1,
M is one or more elements selected from the group consisting of Al, Mg, Mn, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W and Bi , Anode for secondary battery. The method of claim 1,
The lithium transition metal oxide is represented by the following Chemical Formula 2 or Formula 3, the secondary battery positive electrode:
<Formula 2>
Li _{x '} Ni _y' Co _{1-y'-z '} Al _z' O ₂
<Formula 3>
Li _{x '} Ni _y' Co _{1-y'-z '} Mn _z' O ₂
In Formulas 2 and 3, 0.9 ≦ x '≦ 1.2, 0.8 ≦ y' ≦ 0.98, 0 <z '<0.1, and 0 <1-y'-z'<0.2. Forming a cathode active material layer by applying a first composition including a lithium transition metal oxide represented by Formula 1 on at least one surface of a cathode current collector; And
Forming an inorganic layer by applying a second composition including an inorganic material which is an oxide or a hydroxide of at least one metal selected from the group consisting of Mg, Al, and Zn on the cathode active material layer; Manufacturing Method:
<Formula 1>
Li _x Ni _y M _1-y O _2-z A _z
Where
0.9 ≦ x ≦ 1.2, 0.7 ≦ y ≦ 0.98, 0 ≦ z <0.2,
M is at least one oxidation or water +2 or + trivalent metal or transition metal element;
A is at least one oxidation number -1 or -divalent element. A secondary battery positive electrode according to any one of claims 1 to 9;
A cathode disposed opposite the anode; And
And a electrolyte disposed between the positive electrode and the negative electrode.

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