KR20200039260A - Positive electrode for lithium secondary battery, and preparing method of the same - Google Patents

Abstract

The present invention provides a positive electrode for a lithium secondary battery, which is capable of manufacturing a secondary battery having a high energy density without inferior low-temperature output characteristics, and a method of preparing the same. The positive electrode includes a positive electrode active material layer formed on a positive electrode current collector. The positive electrode active material layer includes a lithium transition metal oxide, a conductive material, a binder, and a ceramic-based glass represented by chemical formula 1, Li_1+aAL_xM_ySi_P_3-zO_12+ δ, where M is at least one of Ti and Ge, and 0 < a < 3, 0 < x <= 3, 0 <= y <= 2, 0 <= z <= 2, 0 <= δ <= 3. Moreover, the positive electrode active material layer comprises 0.6-2.9 parts by weight of ceramic-based glass with respect to 100 parts by weight of the sum of the lithium transition metal oxide, the conductive material, and the binder.

Description

Anode for lithium secondary battery and manufacturing method therefor {POSITIVE ELECTRODE FOR LITHIUM SECONDARY BATTERY, AND PREPARING METHOD OF THE SAME}

The present invention relates to a lithium secondary battery positive electrode, a method for manufacturing the positive electrode, and a lithium secondary battery including the positive electrode.

As technology development and demand for mobile devices increase, demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries having high energy density and voltage, long cycle life, and low self-discharge rate have been commercialized and widely used.

Lithium transition metal composite oxides are used as a positive electrode active material for lithium secondary batteries, and lithium cobalt composite metal oxides such as LiCoO ₂ having high working voltage and excellent capacity characteristics are mainly used. However, LiCoO ₂ has very poor thermal properties due to destabilization of the crystal structure due to delithium. In addition, since LiCoO ₂ is expensive, there is a limit to use it in large quantities as a power source in fields such as electric vehicles.

As a material to replace the LiCoO ₂ , lithium manganese composite metal oxides (LiMnO ₂ or LiMn ₂ O _4, etc.), lithium iron phosphate compounds (LiFePO _4, etc.) or lithium nickel composite metal oxides (LiNiO _2, etc.) have been developed. . Among them, research and development of lithium nickel composite metal oxides having a high reversible capacity of about 200 mAh / g and easy to implement a large-capacity battery are being actively researched. However, the LiNiO ₂ is inferior in thermal stability to LiCoO _2, and when an internal short circuit occurs due to pressure from the outside in a charged state, the positive electrode active material itself is decomposed to cause the battery to burst and ignite. Accordingly, as a method for improving low thermal stability while maintaining the excellent reversible capacity of LiNiO ₂ , a lithium nickel cobalt metal oxide in which a part of Ni is replaced with Co and Mn or Al has been developed.

Recently, the demand for a secondary battery having a high energy density is increasing, and accordingly, research for manufacturing a secondary battery having a high energy density by using a lithium transition metal composite oxide having excellent capacity characteristics or by using a high loading electrode is actively conducted. Is going on.

However, when using a lithium transition metal composite oxide exhibiting excellent capacity characteristics as described above or when using a high loading electrode, there is a problem that low-temperature output characteristics are inferior.

Accordingly, there is a need to develop a positive electrode capable of manufacturing a secondary battery having a high energy density without inferior low-temperature output characteristics.

Japanese Patent Publication No. 2014-022204

In order to solve the above problems, the first technical problem of the present invention is to provide an anode capable of improving a high energy density and improving low temperature output characteristics by adding a ceramic-based glass having excellent ion conductivity during anode production.

The second technical problem of the present invention is to provide a method for manufacturing the positive electrode.

The third technical problem of the present invention is to provide a lithium secondary battery including the positive electrode.

The present invention is a positive electrode comprising a positive electrode active material layer formed on a positive electrode current collector, wherein the positive electrode active material layer includes a lithium transition metal oxide, a conductive material, a binder, and a ceramic-based glass represented by Formula 1 below, and the ceramic The system glass provides a positive electrode that is contained in 0.6 parts by weight to 2.9 parts by weight with respect to 100 parts by weight of the total weight of the lithium transition metal oxide, conductive material, and binder.

[Formula 1]

Li _{1 + a} Al _x M _y Si _z P _{3 - z} O _{12 + δ}

In Chemical Formula 1, M is at least one of Ti or Ge, and 0 <a <3, 0 <x≤3, 0≤y≤2, 0≤z≤2, and 0≤δ≤3.

In addition, forming a mixture of a lithium transition metal oxide, a conductive material and a binder dispersed in a solvent; A slurry for forming a positive electrode active material layer is prepared by adding the ceramic glass represented by the following Chemical Formula 1 to the mixture so as to be 0.6 parts by weight to 2.9 parts by weight with respect to 100 parts by weight of the total weight of the lithium transition metal oxide, conductive material, and binder. To do; And applying the slurry for forming the positive electrode active layer on the positive electrode current collector.

[Formula 1]

Li _{1 + a} Al _x M _y Si _z P _{3 - z} O _{12 + δ}

In Chemical Formula 1, M is at least one of Ti or Ge, and 0 <a <3, 0 <x≤3, 0≤y≤2, 0≤z≤2, and 0≤δ≤3.

In addition, it provides a lithium secondary battery comprising the positive electrode according to the present invention.

According to the present invention, by including a positive electrode active material containing a high content of nickel (high-Ni) with an average content of nickel of 60 mol% or more with respect to the total number of moles of transition metal oxides excluding lithium, high capacity characteristics when applied to a battery Can be represented.

In addition, by adding a ceramic glass having excellent ion conductivity to the slurry for forming a positive electrode active material layer for forming the positive electrode active material layer, it not only exhibits high capacity characteristics when applied to the battery, but also provides a secondary battery with improved low temperature output characteristics. You can.

1 is a graph showing the low-temperature output characteristics of the lithium secondary battery prepared in Example 1 and Comparative Examples 1 to 2 of the present invention, respectively.
Figure 2 is a graph showing the capacity characteristics of the lithium secondary battery prepared in Example 1 and Comparative Examples 1 to 2 of the present invention, respectively.
3 is a graph showing the resistance characteristics (Nyquist plot) of lithium secondary batteries prepared in Examples 1 and 2 and 2 of the present invention, respectively.
4 is a graph showing the resistance characteristics of the lithium secondary battery prepared in Example 1 and Comparative Examples 1 to 2 of the present invention, respectively.

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

The terms or words used in the specification and claims should not be interpreted as being limited to ordinary or dictionary meanings, and the inventor can appropriately define the concept of terms in order to best describe his or her invention. Based on the principle that it should be interpreted as meanings and concepts consistent with the technical spirit of the present invention.

anode

Conventionally, in order to manufacture a secondary battery having a high energy density, a lithium transition metal oxide containing a high content of nickel is used as a positive electrode active material, or a high loading electrode is used when manufacturing the electrode.

However, in this case, a secondary battery having a high energy density could be manufactured, but had a disadvantage in that output characteristics were inferior at low temperatures.

Accordingly, the present inventors discovered that a secondary battery with improved energy characteristics as well as high energy density can be produced by adding a ceramic-based glass to a positive electrode active material layer at a specific content during positive electrode manufacturing, and completed the present invention.

Hereinafter, a positive electrode according to the present invention will be described in detail.

The positive electrode according to the present invention is a positive electrode comprising a positive electrode active material layer formed on a positive electrode current collector, wherein the positive electrode active material layer includes a lithium transition metal oxide, a conductive material, a binder, and a ceramic glass represented by the following Chemical Formula 1 The ceramic glass is contained in 0.6 parts by weight to 2.9 parts by weight with respect to 100 parts by weight of the total weight of the lithium transition metal oxide, the conductive material, and the binder.

[Formula 1]

Li _{1 + a} Al _x M _y Si _z P _{3 - z} O _{12 + δ}

In Chemical Formula 1, M is at least one of Ti or Ge, and 0 <a <3, 0 <x≤3, 0≤y≤2, 0≤z≤2, and 0≤δ≤3.

The positive electrode current collector according to the present invention may include a highly conductive metal, and the positive electrode active material layer is easily adhered, but is not particularly limited as long as it is not reactive in the voltage range of the battery. The positive electrode current collector may be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or a surface treated with carbon, nickel, titanium, silver, or the like on an aluminum or stainless steel surface. In addition, the positive electrode current collector may have a thickness of usually 3 to 500 μm, and may form fine irregularities on the current collector surface to increase the adhesion of the positive electrode active material. For example, it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

The positive electrode according to the present invention is formed on the positive electrode current collector, and includes a positive electrode active material layer including a lithium transition metal oxide, a conductive material, a binder, and ceramic glass.

The lithium transition metal oxide may be a layered structure of a positive electrode active material, preferably, the content of nickel with respect to the total number of moles of transition metal oxide excluding lithium may include a high content of nickel or more. . When this is applied to a battery, the capacity characteristics of the battery can be improved as it contains a high content of nickel.

Preferably, the lithium transition metal oxide may be represented by the following formula (2).

[Formula 2]

Li _{1 + a} Ni _b Co _c Mn _d M ¹ _e O ₂

In Chemical Formula 2,

M ¹ is Al, W, Cu, Fe, V, Cr, Ti, Zr, Zn, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B And at least one selected from the group consisting of Mo, 0≤a≤0.1, 0.8≤b <1.0, 0 <c≤0.2, 0 <d≤0.2, 0≤e≤0.2, preferably 0≤a≤ 0.1, 0.8≤b <1.0, 0 <c≤0.2, 0 <d≤0.2, and 0≤e≤0.2.

The positive electrode active material layer includes a ceramic-based glass represented by Formula 1 below.

[Formula 1]

Li _{1 + a} Al _x M _y Si _z P _{3 - z} O _{12 + δ}

In Chemical Formula 1, M is at least one of Ti or Ge, and 0 <a <3, 0 <x≤3, 0≤y≤2, 0≤z≤2, and 0≤δ≤3.

Preferably, the ceramic glass is Li ₃ Al ₁ Ti ₂ Si ₁ P ₂ O ₁₂ , Li _{1 . 5} Al _{0 . 5} Ge _{1 . 5} P ₃ O ₁₂ , Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ , Li ₂ O-Al ₂ O ₃ -SiO ₂ -P ₂ O ₅ -TiO ₂ And Li ₂ O-Al ₂ O ₃ -SiO ₂ -P ₂ O ₅ -TiO ₂ -GeO ₂ It may be to include at least one selected from the group consisting of.

Conventionally, when manufacturing a battery having a high energy density, when the current increases to a certain value or more, the output is also lowered due to a polarization phenomenon in which the voltage of the battery decreases. In particular, the low-temperature output characteristics were inferior due to the polarization phenomenon of lithium ions.

However, in the present invention, the diffusion rate and electrical conductivity of ions are improved by including a ceramic-based glass having excellent ion conductivity represented by the formula (1) in the positive electrode active material layer, so that output characteristics can be improved when the battery is applied. .

The ceramic-based glass is 0.6 parts by weight to 2.9 parts by weight, preferably 0.6 parts by weight to 1.5 parts by weight, more preferably 0.8 parts by weight based on the total weight of the lithium transition metal oxide, the conductive material, and the binder. It may be included in parts by weight to 1.2 parts by weight. For example, when the ceramic-based glass is included in an amount of less than 0.6 parts by weight based on 100 parts by weight of the total amount of the lithium transition metal oxide, the conductive material, and the binder, output according to an effect of improving conductivity according to the addition of the ceramic-based glass, etc. The effect of improving properties may be insignificant, and when it is included in excess of 2.9 parts by weight, the diffusion resistance due to charge transfer increases, so that the output properties may be further deteriorated, and the dispersibility in the positive electrode active material layer is lowered, partial aggregation Symptoms may occur.

In addition, the conductive material included in the positive electrode active material layer is used to impart conductivity to the electrode, and in a battery configured, it can be used without particular limitation as long as it has electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite and artificial graphite; Carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; Metal powders or metal fibers such as copper, nickel, aluminum, and silver; Conductive tubes such as carbon nanotubes; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Or conductive polymers, such as polyphenylene derivatives, etc. are mentioned, and 1 type of these or a mixture of 2 or more types can be used. The conductive material may be included in 10 parts by weight or less, preferably 0.1 parts by weight to 5 parts by weight based on 100 parts by weight of the total weight of the positive electrode active material layer.

The binder included in the positive electrode active material layer serves to improve adhesion between the positive electrode active material particles and adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol (polyvinylalcohol), polyacrylonitrile (polyacrylonitrile), polymethyl meta Polymethymethaxrylate, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene Polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluorine rubber, poly acrylic acid, and a polymer substituted with hydrogen, Li, Na, or Ca, or various copolymers thereof And the like, and among these, one kind alone or a mixture of two or more kinds can be used. The binder may be included in 10 parts by weight or less, preferably 0.1 parts by weight to 5 parts by weight based on 100 parts by weight of the total weight of the positive electrode active material layer.

In addition, the positive electrode active material layer may further include a dispersant.

The dispersant may be used without particular limitation as long as it is used as a dispersant for the positive electrode, and for example, an aqueous dispersant or an organic dispersant may be selectively used as necessary. Preferably, the dispersant is a cellulose-based compound, polyalkylene oxide, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acetal, polyvinyl ether, polyvinyl sulfonic acid, polyvinyl chloride (PVC), polyvinylidene fluorine Ride, chitosan, starch, amylose, polyacrylamide, poly-N-isopropylacrylamide, poly-N, N-dimethylacrylamide, polyethyleneimine, polyoxyethylene, poly (2-methoxye Thoxyethylene), poly (acrylamide-co-diallyldimethylammonium chloride), acrylonitrile / butadiene / styrene (ABS) polymer, acrylonitrile / styrene / acrylic ester (ASA) polymer, acrylonitrile / styrene / acrylic Mixture of ester (ASA) polymer and propylene carbonate, styrene / acrylonitrile (SAN) copolymer, methyl methacrylate / acrylonitrile / butadiene / styrene (MABS) polymer, It is mentioned styrene-butadiene rubber, nitrile butadiene rubber, fluoro rubber or the like, and there is one or a mixture of two or more of them may be used. Hydrogenated nitrile butadiene rubber (H-NBR) can be used. When the positive electrode active material layer further includes a dispersant, the components of the positive electrode active material layer, in particular, can increase the dispersibility of the conductive material, so even if the amount of the conductive material is reduced, the conductivity of the positive electrode active material layer is not reduced, thereby improving electrode resistance. Can improve.

The positive electrode active material layer may have a thickness of 100 μm to 200 μm, preferably 100 μm to 120 μm. For example, when the thickness of the positive electrode active material layer satisfies the above range, since the filling density of the electrode is high, the energy density of the battery including the same may be further increased.

The positive electrode according to the present invention contains a high content of nickel and uses a high loading electrode having a positive electrode active material layer thickness of 100 µm or more, and not only has a high energy density, but also identifies ceramic glass having excellent ion conductivity in the production of the positive electrode. By including as a content, an anode having high energy density and excellent output characteristics is provided.

Manufacturing method of anode

In addition, a method for manufacturing a positive electrode according to the present invention is provided. Specifically, forming a mixture of a lithium transition metal oxide, a conductive material and a binder dispersed in a solvent; Preparing a positive electrode active material slurry by adding the ceramic glass represented by the following Chemical Formula 1 to the mixture so as to be 0.6 parts by weight to 2.9 parts by weight with respect to 100 parts by weight of the total weight of the lithium transition metal oxide, conductive material, and binder; And coating the positive electrode active material slurry on the positive electrode current collector.

[Formula 1]

Li _{1 + a} Al _x M _y Si _z P _{3 - z} O _{12 + δ}

In Chemical Formula 1, M is at least one of Ti or Ge, and 0 <a <3, 0 <x≤3, 0≤y≤2, 0≤z≤2, and 0≤δ≤3.

Looking more specifically, first, a mixture in which a lithium transition metal oxide, a conductive material and a binder are dispersed in a solvent is formed.

The lithium transition metal oxide, conductive material and binder are the same as described above.

The solvent may be a solvent commonly used in the art, dimethyl sulfoxide (DMSO), isopropyl alcohol, isopropyl alcohol, N-methylpyrrolidone (NMP), acetone or Water and the like, and among these, one kind alone or a mixture of two or more kinds can be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, the conductive material, and the binder in consideration of the coating thickness of the slurry and the production yield, and to have a viscosity capable of exhibiting excellent thickness uniformity when applied for the positive electrode production. Do.

The mixture may include lithium transition metal oxide, a conductive material, and a binder in a ratio of (80 to 99.9): (0.1 to 10): (0.1 to 10). When the mixture includes a lithium transition metal oxide, a conductive material, and a binder in the above range, it can not only exhibit excellent capacity characteristics, but also secure appropriate electrode characteristics such as adhesion and electrode resistance.

In addition, with respect to the total weight of 100 parts by weight of the lithium transition metal oxide, the conductive material, and the binder, the dispersant may be 5 parts by weight or less, preferably 0.1 parts by weight to 3 parts by weight. For example, when the mixture further includes the dispersant, it may be used after pre-dispersing the conductive material and the binder and the dispersant in a solvent, and in this case, improving the electrode resistance while reducing the amount of the conductive material can do.

Subsequently, Li _{1 + a} Al _x M _y Si _z P _{3 - z} O _{12 + δ in} the mixture (where M is at least one of Ti or Ge, 0 <a <3, 0 <x≤3, 0 ≤y≤2, 0≤z≤2, 0≤δ≤3) of the ceramic-based glass represented by the lithium transition metal oxide, a conductive material and a binder total weight of 100 parts by weight, 0.6 parts by weight to 2.9 The positive electrode active material slurry is prepared by adding it in parts by weight.

In addition, the addition of the ceramic-based glass to the mixture may be performed by adding the ceramic-based glass in a powder form or by adding a dispersion in which the ceramic-based glass is dispersed in a solvent.

By mixing the ceramic glass with the above content in the mixture to prepare a positive electrode active material slurry, the ionic conductivity of the positive electrode active material slurry is improved, and when applied to the battery, the output characteristics of the secondary battery, particularly at low temperatures The output characteristics of can be improved.

Finally, the positive electrode according to the present invention is prepared by applying the positive electrode active material slurry on the positive electrode current collector, drying and rolling.

Applying the positive electrode active material slurry on the positive electrode current collector can be used without any particular limitation, as long as it is a common method for forming a positive electrode active material layer on the positive electrode current collector, such as coating, dipping, spraying.

Rolling the positive electrode active material slurry may be performed by using a conventional method, and the positive electrode active material layer may have a thickness of 100 μm to 200 μm, preferably 100 μm to 120 μm.

By the above method, a positive electrode having a high energy density as in the present invention and having improved output characteristics, particularly at low temperatures, can be manufactured.

Lithium secondary battery

In addition, the present invention can manufacture an electrochemical device including the anode. The electrochemical device may be specifically a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

Specifically, the lithium secondary battery includes a positive electrode, a negative electrode positioned opposite to the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode, and the positive electrode is the same as described above, so a detailed description is omitted. Hereinafter, only the rest of the configuration will be described in detail.

In addition, the lithium secondary battery may further include a battery container for housing the electrode assembly of the positive electrode, the negative electrode and the separator, and a sealing member for sealing the battery container.

In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper, or the surface of stainless steel Carbon, nickel, titanium, silver or the like, aluminum-cadmium alloy, or the like may be used. In addition, the negative electrode current collector may have a thickness of usually 3 μm to 500 μm, and like the positive electrode current collector, fine irregularities may be formed on the surface of the current collector to enhance the bonding force of the negative electrode active material. For example, it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

The negative active material layer optionally includes a binder and a conductive material together with the negative active material.

As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fibers, and amorphous carbon; Metal compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy or Al alloy; Metal oxides capable of doping and dedoping lithium such as SiO _β (0 <β <2), SnO ₂ , vanadium oxide, and lithium vanadium oxide; Or a complex containing the metal compound and the carbonaceous material, such as a Si-C composite or a Sn-C composite, and the like, or any one or a mixture of two or more thereof may be used. In addition, a metal lithium thin film may be used as the negative electrode active material. In addition, both low crystalline carbon and high crystalline carbon can be used as the carbon material. Soft carbon and hard carbon are typical examples of low crystalline carbon, and amorphous or plate-like, scaly, spherical or fibrous natural graphite or artificial graphite, and kissy graphite are examples of high crystalline carbon. graphite), pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch derived cokes).

The negative electrode active material may be included in 80 parts by weight to 99 parts by weight based on the total weight of the negative electrode active material layer.

The binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and is usually added in an amount of 0.1 to 10 parts by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoro Roethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluorine rubber, and various copolymers thereof.

The conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 parts by weight or less, preferably 5 parts by weight or less based on the total weight of the negative electrode active material layer. The conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, graphite such as natural graphite or artificial graphite; Carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

For example, the negative electrode active material layer is prepared by coating and drying a negative electrode active material layer-forming composition prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material on a negative electrode current collector, or drying the negative electrode. It can be produced by casting the composition for forming an active material layer on a separate support, and then laminating the film obtained by peeling from the support on a negative electrode current collector.

The negative electrode active material layer is, for example, a negative electrode active material, and optionally a binder and a conductive material are dissolved or dispersed in a solvent on a negative electrode current collector to apply and dry a composition for forming a negative electrode active material layer, or for drying the negative electrode active material layer. It can also be prepared by casting the composition on a separate support and then laminating the film obtained by peeling from the support on a negative electrode current collector.

On the other hand, in the lithium secondary battery, the separator separates the negative electrode from the positive electrode and provides a passage for lithium ions, and is usually used as a separator in a lithium secondary battery, and can be used without particular limitation. It is desirable to have low resistance and excellent electrolyte-moisturizing ability. Specifically, porous polymer films such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer, etc. A laminate structure of two or more layers of may be used. In addition, a conventional porous non-woven fabric, for example, a high-melting point glass fiber, non-woven fabric made of polyethylene terephthalate fiber or the like may be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may be used in a single-layer or multi-layer structure.

Further, examples of the electrolyte used in the present invention include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, and melted inorganic electrolytes that can be used in the manufacture of lithium secondary batteries. It does not work.

Specifically, the electrolyte may include an organic solvent and a lithium salt.

The 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 organic solvent, methyl acetate (methyl acetate), ethyl acetate (ethyl acetate), γ-butyrolactone (γ-butyrolactone), ε-caprolactone (ε-caprolactone), such as ester solvents; Ether-based solvents such as dibutyl ether or tetrahydrofuran; Ketone solvents such as cyclohexanone; Aromatic hydrocarbon-based solvents such as benzene and fluorobenzene; Dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate (propylene carbonate, PC) and other carbonate-based solvents; Alcohol solvents such as ethyl alcohol and isopropyl alcohol; Nitriles such as R-CN (R is a straight-chain, branched or cyclic hydrocarbon group having 2 to 20 carbon atoms, and may include a double bond aromatic ring or ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; Alternatively, sulfolanes may be used. Among them, carbonate-based solvents are preferred, and cyclic carbonates (for example, ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant capable of increasing the charge and discharge performance of the battery, and low-viscosity linear carbonate-based compounds ( For example, a mixture of ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) is more preferable. In this case, the mixture of the cyclic carbonate and the chain carbonate in a volume ratio of about 1: 1 to about 1: 9 may be used to exhibit excellent electrolyte performance.

The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. 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 .} LiCl, LiI, or LiB (C ₂ O ₄ ) ₂ and the like can be used. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0M. When the concentration of the lithium salt is included in the above range, since the electrolyte has an appropriate conductivity and viscosity, it can exhibit excellent electrolyte performance, and lithium ions can be effectively moved.

In addition to the components of the electrolyte, the electrolyte includes haloalkylene carbonate-based compounds such as difluoro ethylene carbonate, pyridine, and tree for the purpose of improving the life characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery. Ethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N, N-substituted imida One or more additives such as zolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol or aluminum trichloride may also be included. At this time, the additive may be included in 0.1 to 5 parts by weight based on 100 parts by weight of the total electrolyte.

Since the lithium secondary battery comprising the positive electrode active material according to the present invention as described above stably exhibits excellent discharge capacity, output characteristics and life characteristics, portable devices such as mobile phones, notebook computers, digital cameras, and hybrid electric vehicles ( It is useful for electric vehicle fields such as hybrid electric vehicle (HEV).

Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

The battery module or battery pack includes a power tool; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); Alternatively, it may be used as a power supply for any one or more of medium and large devices in a power storage system.

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be a cylindrical shape, a square shape, a pouch shape or a coin shape using a can.

The lithium secondary battery according to the present invention can be used not only for a battery cell used as a power source for a small device, but also as a unit battery in a medium-to-large battery module including a plurality of battery cells.

Hereinafter, examples will be described in detail to specifically describe the present invention. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

Example

Example  One

LiNi _{0 . 8} Co _{0 . 1} Mn _{0 . 1} O ₂ , a carbon black conductive material, a polyvinylidene fluoride binder and an H-NBR dispersant were mixed in a weight ratio of 97.5: 1: 1.35: 0.15, and mixed in an NMP solvent to prepare a mixture. LiNi _{0 . 8} Co _{0 . 1} Mn _{0 . 1} O ₂ , carbon black conductive material, polyvinylidene fluoride binder total weight of 100 parts by weight of Li ₃ Al ₁ Ti ₂ Si ₁ P ₂ O _{12 in} an amount of 1 part by weight By adding ceramic glass, an anode slurry composition was prepared.

The positive electrode slurry composition prepared above was applied to an Al foil having a thickness of 15 μm to a thickness of 150 μm, dried at 130 ° C., and rolled to prepare a positive electrode having a thickness of 100 μm.

Meanwhile, as a negative electrode active material, a graphite, carbon black conductive material, and polyvinylidene fluoride binder were mixed in a weight ratio of 95: 2: 3 and added to NMP, a solvent, to prepare a composition for forming a negative electrode. The negative electrode composition was coated on a copper foil having a thickness of 15 μm to a thickness of 120 μm, dried, and then roll-pressed to prepare a negative electrode.

The positive electrode and the negative electrode prepared above were laminated together with a polyethylene separator to prepare an electrode assembly, and then placed in a battery case, dissolved 1 M LiPF ₆ in a mixed solvent mixed with ethylene carbonate: ethyl methyl carbonate in a volume ratio of 7: 3. The prepared electrolyte was injected to prepare a lithium secondary battery.

Comparative example  One

In preparing the positive electrode slurry composition of Example 1, a positive electrode for a secondary battery and a lithium secondary battery including the same were prepared in the same manner as in Example 1, except that no ceramic glass was added.

Comparative example  2

When preparing the positive electrode slurry composition of Example 1, to the mixture, LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , carbon black conductive material, polyvinylidene fluoride binder, ceramic glass was added so that 5 parts by weight based on 100 parts by weight Except for that, in the same manner as in Example 1, a positive electrode for a secondary battery and a lithium secondary battery comprising the same were manufactured.

Experimental example  1: Evaluation of low temperature output characteristics

The low temperature output characteristics of each of the lithium secondary batteries prepared in Example 1 and Comparative Examples 1 and 2 were measured.

Specifically, the lithium secondary batteries prepared in Example 1 and Comparative Examples 1 to 2 were discharged at -10 ° C by △ SOC 15 (SOC 35% to SOC 20%) to 2.5V at -10 ° C, respectively. The change was confirmed, and the current value at SOC 20% was confirmed. The results are shown in Table 1 below and FIG. 1. Specifically, the termination current (end I) value of the lithium secondary batteries prepared in Example 1 and Comparative Examples 1 to 2 was confirmed through FIG. 1, and this was divided into initial capacity to confirm C-rate at the termination current.

Termination current (C-rate) Example 1 0.56C Comparative Example 1 0.51C Comparative Example 2 0.50C

The output was calculated by using the current difference generated when the secondary batteries prepared in Examples 1 and 1 and 2 were discharged by -SOC 15 at -10 ° C. As shown in Table 1, the secondary battery prepared in Example 1 has a current value of 10 at SOC 20% compared to the secondary batteries prepared in Comparative Examples 1 and 2 in which ceramic glass is not added or ceramic glass is excessively added. It was confirmed that it was about% higher. Through this, it was confirmed that a higher current was exhibited in the same state of charge, and thus, it was predicted that the output characteristic at the low temperature of Example 1 would be the best.

Experimental example  2: Capacity characteristics evaluation

The capacity characteristics of each of the lithium secondary batteries prepared in Example 1 and Comparative Examples 1 and 2 were evaluated.

Specifically, after discharging to 2.5V with a constant current of 0.33C at room temperature for each of the lithium secondary batteries prepared in Example 1 and Comparative Examples 1 to 2, the discharge capacity was measured, and this is shown in FIG. 2.

As shown in Figure 2, in the case of the secondary battery prepared in Example 1, by adding an appropriate amount of ceramic-based glass does not occur the energy density reduction phenomenon due to the addition of the ceramic-based glass, the capacity characteristics of the comparative advantage of Comparative Example 1 It was confirmed that it showed. However, in the case of the secondary battery prepared in Comparative Example 2, it was confirmed that the energy density of the active material layer was lowered due to the addition of the ceramic-based glass by adding the ceramic-based glass beyond the range of the present invention.

Experimental example  3: Evaluation of resistance characteristics

The resistance characteristics of each of the lithium secondary batteries prepared in Example 1 and Comparative Examples 1 and 2 were evaluated.

Specifically, after the lithium secondary battery was discharged under the conditions of 2.5C in the range of 3.65V to 3.68V driving voltage at room temperature (25 ° C), the resistance of the battery was measured at SOC 50%, and the results are plotted. 3 and 4.

Specifically, the lithium secondary batteries prepared in Examples 1 and Comparative Examples 1 and 2 were measured for positive electrode resistance by an AC impedance method at different frequencies using an impedance analyzer (potentiostat VMPM3, biology), and the resulting age The quist plot is shown in FIG. 3 (frequency range: 10 kHz to 100 mHz). As shown in FIG. 3, in the case of the secondary battery prepared in Example 1, it exhibited similar resistance characteristics to the secondary battery prepared in Comparative Example 1, and exhibited higher impedance characteristics than the arch battery prepared in Comparative Example 2. . Specifically, the secondary battery prepared in Comparative Example 2 increases the diffusion resistance due to charge transfer by adding ceramic-based glass beyond the range of the present invention, and accordingly, the battery associated with the position and size of the semicircle in the drawing of FIG. 3. It was confirmed that the interface resistance increased.

On the other hand, as shown in Figure 4, in the case of the secondary battery prepared in Example 1, it was confirmed that the increase in resistance over time significantly decreased compared to the secondary battery prepared in Comparative Example 2, which was confirmed in FIG. Similarly, it could be predicted that the surface was stabilized by reducing the interface resistance.

Claims (10)

As a positive electrode comprising a positive electrode active material layer formed on the positive electrode current collector,
The positive electrode active material layer includes a lithium transition metal oxide, a conductive material, a binder, and a ceramic-based glass represented by Formula 1 below,
The ceramic-based glass, the lithium transition metal oxide, the conductive material and the total weight of the combined binder 100 parts by weight, 0.6 parts by weight to 2.9 parts by weight, the positive electrode.
[Formula 1]
Li _{1 + a} Al _x M _y Si _z P _{3 - z} O _{12 + δ}
In Chemical Formula 1, M is at least one of Ti or Ge, and 0 <a <3, 0 <x≤3, 0≤y≤2, 0≤z≤2, and 0≤δ≤3.
According to claim 1,
The ceramic glass is Li ₃ Al ₁ Ti ₂ Si ₁ P ₂ O ₁₂ , Li _{1 . 5} Al _{0 . 5} Ge _{1 . 5} P ₃ O ₁₂ , Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ , Li ₂ O-Al ₂ O ₃ -SiO ₂ -P ₂ O ₅ -TiO ₂ And at least one selected from the group consisting of Li ₂ O-Al ₂ O ₃ -SiO ₂ -P ₂ O ₅ -TiO ₂ -GeO ₂ .
According to claim 1,
The lithium transition metal oxide is to be represented by the formula (2), the positive electrode.
[Formula 2]
Li _{1 + a} Ni _b Co _c M ¹ _d M ² _e O ₂
In Chemical Formula 2,
M ¹ is at least one of Mn or Al,
M ² is Al, W, Cu, Fe, V, Cr, Ti, Zr, Zn, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B And at least one selected from the group consisting of Mo, and 0≤a≤0.1, 0.6≤b <1.0, 0 <c≤0.4, 0 <d≤0.4, and 0≤e≤0.2.
According to claim 1,
The lithium transition metal oxide is to be represented by the formula (3), the positive electrode.
[Formula 3]
Li _{1 + a} Ni _b Co _c Mn _d O ₂
In Chemical Formula 3, 0≤a≤0.1, 0.8≤b <1.0, 0 <c≤0.2, and 0 <d≤0.2.
According to claim 1,
The positive electrode active material layer has a thickness of 100 μm to 200 μm.
According to claim 1,
The positive electrode active material layer is to further include a dispersant, the positive electrode.
According to claim 1,
The mixture will include a lithium transition metal oxide, a conductive material and a binder in a ratio of (80 to 99.9): (0.1 to 10): (0.1 to 10), the positive electrode.
The method of claim 6,
The lithium transition metal oxide, the conductive material and the binder further comprises 5 parts by weight or less of the dispersant relative to the total weight of 100 parts by weight, the positive electrode.
Forming a mixture in which a lithium transition metal oxide, a conductive material, and a binder are dispersed in a solvent;
Preparing a positive electrode active material slurry by adding the ceramic glass represented by the following Chemical Formula 1 to the mixture so as to be 0.6 parts by weight to 2.9 parts by weight with respect to 100 parts by weight of the total weight of the lithium transition metal oxide, conductive material, and binder; And
Coating the positive electrode active material slurry on the positive electrode current collector.
[Formula 1]
Li _{1 + a} Al _x M _y Si _z P _{3 - z} O _{12 + δ}
In Chemical Formula 1, M is at least one of Ti or Ge, and 0 <a <3, 0 <x≤3, 0≤y≤2, 0≤z≤2, and 0≤δ≤3.
A lithium secondary battery comprising the positive electrode according to claim 1.

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