KR102047256B1 - Cathode active material for lithium secondary battery and methode of manufacturing the same - Google Patents

Abstract

A positive electrode active material for a lithium secondary battery comprises lithium metal oxide particles, and a thio-coating formed on at least a part of the surface of the lithium metal oxide particles and derived from a thio-based compound including a double bond containing sulfur elements. Through the thio-coating, chemical stability of the lithium metal oxide particles is improved and surface by-products are reduced.

Description

Cathode active material for lithium secondary battery and manufacturing method thereof {CATHODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY AND METHODE OF MANUFACTURING THE SAME}

Embodiments of the present invention relate to a cathode active material for a lithium secondary battery and a method of manufacturing the same. More specifically, the present invention relates to a cathode active material for a lithium metal oxide-based lithium secondary battery and a method of manufacturing the same.

The rechargeable battery is a battery that can be repeatedly charged and discharged, and is widely used as a power source of portable electronic communication devices such as a camcorder, a mobile phone, a notebook PC, etc. according to the development of the information communication and display industries. In recent years, battery packs including secondary batteries have been developed and applied as a power source of environmentally friendly vehicles such as hybrid vehicles.

Examples of secondary batteries include lithium secondary batteries, nickel-cadnium batteries, and nickel-hydrogen batteries. Among them, lithium secondary batteries have high operating voltage and high energy density per unit weight, and are advantageous in terms of charging speed and light weight. In this regard, research and development is actively progressing.

The lithium secondary battery may include an electrode assembly including a positive electrode, a negative electrode, and a separator (separator), and an electrolyte impregnating the electrode assembly. The lithium secondary battery may further include, for example, a pouch type exterior material containing the electrode assembly and the electrolyte.

Lithium metal oxide may be used as an active material for a positive electrode of a lithium secondary battery. Examples of the lithium metal oxide include nickel-based lithium metal oxides.

As the application range of the lithium secondary battery is expanded, longer lifespan, high capacity, and operation stability are required. In the lithium metal oxide used as the active material for the positive electrode, when the non-uniformity of the chemical structure is caused due to the deposition of lithium, it may be difficult to implement a lithium secondary battery having a desired capacity and lifespan. In addition, if the lithium metal oxide structure is deformed or damaged during repeated charge / discharge cycles, lifespan stability and capacity retention characteristics may be degraded.

For example, Korean Patent Publication No. 10-0821523 discloses a method of removing lithium salt impurities by washing a lithium composite metal oxide with water, but there is a limit in removing sufficient impurities, and particle surface damage in a washing process is limited. May be caused.

Korea Patent Publication No. 10-0821523

One object of the present invention is to provide a cathode active material for a lithium secondary battery with improved operational stability and electrical properties and a method of manufacturing the same.

One object of the present invention is to provide a lithium secondary battery with improved operation stability and electrical characteristics.

A cathode active material for a lithium secondary battery according to exemplary embodiments may be formed from lithium metal oxide particles and a thio-based compound formed on at least part of the surface of the lithium metal oxide particles and having a double bond containing a sulfur atom. Thio-coatings.

In some embodiments, the thio-based compound is a thiosulfate compound comprising a thioamide compound represented by the following Formula 1, a trithiocarbonate compound represented by the following Formula 2, or a thiosulfate ion represented by the following Formula 3. It may include at least one of.

 [Formula 1]

(In formula 1, R ₁ is a hydrogen atom, halogen, O ^- or S ^- containing salt, a hydrocarbon group of 1 to 10 carbon atoms that can be substituted with a substituent, an alkoxy group of 1 to 10 carbon atoms, an amine group, an alkyl group of 1 to 10 carbon atoms) An amine group substituted with a thioalkyl group or thioamide group having 1 to 10 carbon atoms,

R ₂ and R ₃ are each independently a hydrocarbon group having 1 to 10 carbon atoms which may be substituted with a hydrogen atom or a substituent, and R ₂ and R ₃ may be bonded to each other to form a ring, and R ₁ , R ₂ and R ₃ may be Bondable substituents include halogen, cyano, hydroxyl or carboxyl groups).

[Formula 2]

(In Formula 2, R ¹ and R ² are each independently a hydrocarbon group having 10 to 1 carbon atoms which may be substituted with a hydrogen atom or a substituent, R ¹ and R ² may be bonded to each other to form a ring, and R ¹ and R The substituent capable of bonding to ² includes a halogen, cyano group, hydroxyl group or carboxyl group)

[Formula 3]

In some embodiments, the it included in the formula R ₁ of 1 O ^- or S ^- containing salt is an alkali metal cation, N ⁺ R ₄ or represents a salt with the P ⁺ R _4, R ₄ is a hydrogen atom or a C 1 It may be an alkyl group of 8 to.

In some embodiments, the hydrocarbon group included in R ₁ R ₂ , and R ₃ in Formula 1 may be a carbon-carbon double bond, —O—, —S—, —CO—, —OCO—, —SO— , -CO-O-, -O-CO-O-, -S-CO-, -S-CO-O-, -CO-NH-, -NH-CO-O-, -NR'-,> P Or substituted or linked by at least one selected from the group consisting of ═O, —SS—, and —SO ₂ —, and R ′ may be a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

In some embodiments, the thioamide compound may include at least one of the compounds of Formulas 1 to 19.

[Formula 1] [Formula 2] [Formula 3]

[Formula 4] [Formula 5] [Formula 6]

[Formula 7] [Formula 8] [Formula 9]

[Formula 10] [Formula 11]

[Formula 12] [Formula 13]

[Formula 14] [Formula 15] [Formula 16]

[Formula 17] [Formula 18] [Formula 19]

In some embodiments, the trithiocarbonate compound may include at least one of the compounds of Formula 20 or Formula 21 below.

[Formula 20] [Formula 21]

In some embodiments, the thiosulfate compound may include at least one of salts represented by the following Chemical Formula 22, Chemical Formula 23, or Chemical Formula 24.

[Formula 22] [Formula 23] [Formula 24]

.

.

In some embodiments, the lithium metal oxide particles may include lithium nickel-based metal oxides represented by the following general formula (1).

[Formula 1]

Li _x Ni _y M _y-1 O ₂

(In Formula 2, 0.95 <x <1.08, y ≧ 0.5, and M is at least one element selected from the group consisting of Co, Mn, Al, Zr, Ti, B, Mg, Ba).

In some embodiments, in Formula 1, 0.8 ≦ y ≦ 0.93.

In some embodiments, in Formula 1, M may include Co and Mn.

In some embodiments, the lithium metal oxide particles may include a doping or coating comprising at least one of Al, Zr or Ti.

In some embodiments, the thio-coating may have a coating layer, ligand bond or complex bond form on the surface of the lithium metal oxide particles.

In some embodiments, the lithium metal oxide particles have a layered structure, and the thio-coating may coat a grain boundary of a surface portion of the lithium metal oxide particles.

In the method of manufacturing a cathode active material for a lithium secondary battery according to exemplary embodiments, lithium metal oxide particles are manufactured. The lithium metal oxide particles are washed with a cleaning liquid containing a thio-based compound having a double bond containing a sulfur atom.

In some embodiments, the amount of the thio-based compound added may be 0.05 to 2 wt% based on the total weight of the lithium metal oxide particles.

In some embodiments, the amount of the thio-based compound added may be 0.1 to 1 wt% based on the total weight of the lithium metal oxide particles.

In some embodiments, the lithium metal oxide particles may be mixed and heat treated with at least one of Al ₂ O ₃ , ZrO _2, or TiO ₂ before the cleaning to form a coating.

In some embodiments, the thio-based compound may comprise a thioamide compound, a trithiocarbonate compound and / or a thiosulfate compound.

Lithium secondary batteries according to exemplary embodiments are thio-derived from thio-based compounds formed on lithium metal oxide particles and at least a portion of the surface of the lithium metal oxide particles and having double bonds containing sulfur atoms. A positive electrode including a positive electrode active material including a coating; cathode; And a separator disposed between the anode and the cathode.

According to embodiments of the present invention, a thio-coating may be formed on the surface of the lithium metal oxide particles to suppress side reaction with the electrolyte while maintaining the stability of the layered structure of the lithium metal oxide particles. In some embodiments, for example, a metal ion complex may be formed by the thio-coating upon damage of the layered structure of the lithium metal oxide particles. Therefore, thio-coating may increase the structure or crystal stability, thereby significantly improving the stability and capacity / output retention characteristics of the positive electrode active material.

According to exemplary embodiments, the thio-coating may be introduced through a cleaning process using a cleaning solution containing a thioamide compound, a trithiocarbonate compound, and / or a thiosulfate compound. Accordingly, impurities such as lithium salt precipitates remaining on the surface of the lithium metal oxide particles may be removed together while the thio-coating is formed.

<Positive Active Material for Lithium Secondary Battery and Manufacturing Method Thereof>

A cathode active material for a rechargeable lithium battery according to exemplary embodiments (hereinafter, may be abbreviated as a cathode active material) may include lithium metal oxide particles and a thio-coating formed on the surface of the lithium metal oxide particles. .

The term "lithium metal oxide" as used herein refers to a composite oxide comprising lithium and at least one metal other than lithium. In example embodiments, the lithium metal oxide particles may include lithium nickel-based metal oxides.

For example, the lithium nickel-based metal oxide may be represented by the following general formula (1).

[Formula 1]

Li _x Ni _y M _y-1 O ₂

In Formula 2, 0.95 <x <1.08, y ≧ 0.5, and M may be at least one element selected from the group consisting of Co, Mn, Al, Zr, Ti, B, Mg, and Ba.

Nickel (Ni) may be provided as a metal associated with the capacity of a lithium secondary battery. For example, the higher the nickel content, the higher the capacity and output of the lithium secondary battery.

In one embodiment, in order to implement a high-capacity, high-output positive electrode active material may be 0.8≤y≤0.93 in the general formula (1).

M may include cobalt (Co) and manganese (Mn) to supplement stable electrical conductivity and chemical stability due to the high content of nickel. For example, cobalt (Co) may be a metal associated with the conductivity or resistance of a lithium secondary battery. In one embodiment, M comprises manganese (Mn), Mn may be provided as a metal associated with the mechanical and electrical stability of the lithium secondary battery.

Accordingly, the lithium metal oxide particles may include a nickel-cobalt-manganese-based lithium oxide, and may be provided with a cathode active material having improved capacity, output, low resistance, and lifetime stability.

In some embodiments, the lithium metal oxide particles may further include doping or coating in addition to Ni, Co and Mn. For example, the doping or coating may contain Al, Zr and / or Ti, preferably Al, Zr and Ti.

In the nickel-cobalt-manganese-based lithium oxide, the content of the doping element is about 0.1 to 1 mol% based on the total moles of Ni, Co, Mn and doping elements (eg, Al, Zr and / or Ti). And preferably about 0.5 to 1 mol%. Within this range, chemical and structural stability can be further improved without excessively lowering the activity of the lithium metal oxide particles.

The coating may be derived from a coating metal oxide such as Al ₂ O ₃ , ZrO ₂ and / or TiO ₂ . The amount of the coating metal oxide added to form a coating may be about 0.5 to 1 wt% based on the total weight of the nickel-cobalt-manganese-based lithium oxide.

In some embodiments, the lithium metal oxide particles may have a layered structure. For example, the lithium nickel-based metal oxide primary particles may be aggregated to form a layered structure to form the lithium metal oxide particles as a cathode active material. Through the particle structure, mobility of lithium ions generated in the cathode active material may be further improved.

The thio-coating may be formed on the surface of the lithium metal oxide particles described above.

The term "thio-coating" as used in the present application is used to encompass a coating layer formed substantially entirely on the surface of the lithium metal oxide particles, and a coating layer formed on a portion of the surface of the lithium metal oxide particles.

In some embodiments, the thio-coating may include an organic ligand bond attached to the surface of the lithium metal oxide particles or an organo-metal complex with metal ions exposed on the surface of the lithium metal oxide particles.

In some embodiments, the thio-coating may coat a grain boundary of the surface portion of the lithium metal oxide particles.

The thio-coating may be derived from a compound comprising a double bond containing a sulfur atom (eg S = S or S = C). According to exemplary embodiments, the thio-coating may be derived from at least one of a thioamide compound, a tri-thiocarbonate compound, or a thiosulfate compound.

In the present specification, a thioamide compound may be used to mean a thioamide salt together.

In some embodiments, the thioamide compound may include a compound represented by Structural Formula 1 below.

[Formula 1]

Of formula 1, R ₁ is a hydrogen atom, a halogen, ^O-a containing salt, substituted with a substituent capable C 1 of 10 of the hydrocarbon group, an alkoxy group having 1 to 10 carbon atoms, an amine group, an alkyl group having 1 to 10 carbon atoms ^- or S Substituted amine groups, thioalkyl groups having 1 to 10 carbon atoms, or thioamide groups.

As used herein, the term "hydrocarbon group" may include cyclic aliphatic groups, linear aliphatic groups, aromatic groups or combinations thereof. For example, the hydrocarbon group may be an alkyl group, an alkenyl group (for example, 2 to 10 carbon atoms), an aryl group (for example, 6 to 10 carbon atoms), an aryl alkyl group (for example, 7 to 10 carbon atoms), or cyclo An alkyl group (for example, 3 to 10 carbon atoms) or a heterocyclic group (for example, 5 to 10 carbon atoms) may be included. Examples of the substituent capable of bonding to the hydrocarbon group include a halogen, cyano group, hydroxyl group, carboxyl group and the like.

The hydrocarbon group included in R ₁ is a carbon-carbon double bond, -O-, -S-, -CO-, -OCO-, -SO-, -CO-O-, -O-CO-O-,- S-CO-, -S-CO-O-, -CO-NH-, -NH-CO-O-, -NR'-,> P = O, -SS- and -SO _2- Substituted or linked by at least one, R 'may be a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

It said included in R ₁ O ^- or S ^- containing salt is O ^- or S ^-, and alkali metal cation / alkaline earth metal cations ^{(e.g., Li +, Na +, K} +, Cs + Ca 2+, Mg 2 ⁺ ), A salt or an ionic bond with N ⁺ R ₄ or P ⁺ R ₄ , and R ₄ may be a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

In Structural Formula 1, R ₂ and R ₃ may each independently be a hydrogen atom or a hydrocarbon group having 10 carbon atoms in 1 that may be substituted with a substituent. The hydrocarbon group included in R ₂ and R ₃ may be, for example, an alkyl group, an alkenyl group (for example, 2 to 10 carbon atoms), an aryl group (for example, 6 to 10 carbon atoms), or an aryl alkyl group (for example, , 7 to 10 carbon atoms, cycloalkyl group (for example, 3 to 10 carbon atoms) or heterocyclic group (for example, 5 to 10 carbon atoms) may be included. Examples of the substituent capable of bonding to the hydrocarbon group include a halogen, cyano group, hydroxyl group, carboxyl group and the like.

The hydrocarbon group included in R ₂ and R ₃ is a carbon-carbon double bond, -O-, -S-, -CO-, -OCO-, -SO-, -CO-O-, -O-CO-O -, -S-CO-, -S-CO-O-, -CO-NH-, -NH-CO-O-, -NR'-,> P = O, -SS- and -SO _2- Substituted or linked by at least one selected from the group, R '' may be a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

In some embodiments, R ₂ and R ₃ can be fused to each other to form a ring. For example, R ₂ and R ₃ are fused together (e.g., a cyclic ether) heterocycle can be formed.

In some embodiments, the thioamide compound may be represented by the following Chemical Formula 1 (thiosemicarbazide), Chemical Formula 2 (thiourea), Chemical Formula 3 (O-ethyl carbamothioate), Chemical Formula 4 (thioacetamide), Chemical Formula 5 (dithiooxamide), Chemical Formula 6 ( dimethylcarbamothioic chloride), formula 7 (N, N-dimethylmethanethioamide), formula 8 (Tetramethylthiuram monosulfide), formula 9 (Tetramethylthiuram disulfide), formula 10 (N, N-dimethylmorpholine-4-carbothioamide), formula 11 (N-cyclohexylmorpholine-4 -carbothioamide), formula 12 (((ethylthio) carbonothioyl) glycine), formula 13 (2- (4-oxo-2-thioxothiazolidin-3-yl) acetic acid), or at least one of the compounds of formulas 14-19 It may include.

 [Formula 1] [Formula 2] [Formula 3]

[Formula 4] [Formula 5] [Formula 6]

[Formula 7] [Formula 8] [Formula 9]

[Formula 10] [Formula 11]

[Formula 12] [Formula 13]

[Formula 14] [Formula 15] [Formula 16]

[Formula 17] [Formula 18] [Formula 19]

The trithiocarbonate compound may include a compound represented by the following Structural Formula 2.

[Formula 2]

Structure 2 of, R ¹ and R ² are of the formula 1, R ₂ and R ₃ may be each independently a hydrocarbon group of the optionally substituted C 1 10 of a hydrogen atom, or a substituent. The hydrocarbon group included in R ¹ and R ² may be, for example, an alkyl group (eg, having 1 to 10 carbon atoms), an alkenyl group (eg, having 2 to 10 carbon atoms), an aryl group (eg, having 6 carbon atoms). To 10), an aryl alkyl group (for example, 7 to 10 carbon atoms), a cyclo alkyl group (for example, 3 to 10 carbon atoms) or a heterocyclic group (for example, 5 to 10 carbon atoms) may be included. Examples of the substituent capable of bonding to the hydrocarbon group include a halogen, cyano group, hydroxyl group, carboxyl group and the like.

R ¹ and R ² may be fused to each other to form a ring. For example, R ¹ and R ² may be fused to each other to form a hetero ring.

In some embodiments, the trithiocarbonate compound may include at least one of the compounds of Formula 20 or Formula 21.

[Formula 20] [Formula 21]

The thiosulfate compound may include a salt containing an ion represented by the following Structural Formula 3.

[Formula 3]

For example, the thiosulfate compound may include at least one of salts represented by the following Chemical Formula 22, Chemical Formula 23, or Chemical Formula 24.

[Formula 22] [Formula 23] [Formula 24]

A thio-based compound including the thioamide compound, trithiocarboate compound or thiosulfate compound described above may form a coating layer, a ligand bond or a complex on the surface of the lithium metal oxide particles, for example. Can be. Therefore, the surface of the lithium metal oxide particles can be effectively protected, and for example, the lithium metal oxide particles can be protected from side reaction with an electrolyte solution.

Even when the layer structure of the lithium metal oxide particles is deformed or collapsed due to repetition of charge and discharge, the thio-based compound forms a bond or complex with the metal ions to which it is exposed or released to generate by-products by side reaction of the metal ions. You can prevent it.

In addition, as described above, when the lithium metal oxide particles include additional metal doping or coating, chemical stability of the positive electrode active material may be further improved by bonding with the thio-based compound with the metal doping or coating. .

Hereinafter, a method of manufacturing the cathode active material will be described in more detail.

In example embodiments, the lithium metal oxide particles may be prepared by reacting a lithium precursor and a nickel precursor. The lithium precursor and the nickel precursor may include oxides or hydroxides of lithium and nickel, respectively. For example, the preliminary lithium metal oxide may be obtained by reacting the lithium precursor and the nickel precursor in a solution through a precipitation reaction such as coprecipitation.

In some embodiments, in addition to the lithium precursor and the nickel precursor, other metal precursors (eg, cobalt precursor, manganese precursor, etc.) may be used together to react. In some embodiments, the lithium precursor and the nickel-cobalt-manganese precursor (eg nickel-cobalt-manganese hydroxide) may be used together.

The other metal precursor may include Al, Zr and / or Ti precursors in addition to the cobalt precursor and manganese precursor in consideration of doping formation.

In some embodiments, after the lithium metal oxide particles are manufactured, a firing process may be further performed. For example, the firing process may be performed at a temperature of about 600 to 1000 ℃. The layer structure of the lithium metal oxide particles may be stabilized by the firing process, and a doping element may be fixed.

In some embodiments, the prepared lithium metal oxide particles may be mixed with a coating metal oxide such as Al ₂ O ₃ , ZrO _2, and / or TiO ₂ , followed by further heat treatment to form a coating.

According to exemplary embodiments, the lithium metal oxide particles may be cleaned or washed using a cleaning solution including the thio-based compound described above.

Unreacted precursors may remain or precipitate on the surface of the lithium metal oxide particles synthesized through the aforementioned precursor reaction. In addition, impurities and solution molecules in the synthesis process may remain on the lithium metal oxide particles.

In some embodiments, the lithium precursor may be used in excess to improve the yield of the lithium metal oxide particles or to stabilize the synthesis process. In this case, lithium salt impurities including lithium hydroxide (LiOH) and lithium carbonate (Li ₂ CO ₃ ) may remain on the surface of the preliminary lithium metal oxide.

The lithium salt impurity may be collected and removed by the thio-based compound compound included in the cleaning solution. In the comparative example, when the washing process using water may be performed, the lithium salt impurities may be removed, but oxidation of the surface of the lithium metal oxide particles and side reaction with water may be caused to damage or collapse the layered structure of the positive electrode active material. Can cause. In addition, as the layered structure is denatured into a spinel structure and / or a rock salt structure by water, lithium-nickel oxide may be hydrolyzed to generate nickel impurities such as NiO or Ni (OH) ₂ .

However, according to exemplary embodiments, since the cleaning process is performed using the cleaning solution including the thio-based compound, metal bonding of the thio-based compound is prevented while preventing oxidation and layer structure damage by water on the particle surface. Through lithium salt impurities can be effectively removed.

In addition, since the thio-coating is formed as described above together with the cleaning process, impurity removal and particle surface protection can be simultaneously implemented.

In some embodiments, the amount of the thio-based compound added may be about 0.05 to 2 wt% based on the total weight of the lithium metal oxide particles. Sufficient coating or passivation effects can be obtained without excessively inhibiting the activity of the metal contained in the positive electrode active material within the above range.

Preferably, the amount of the thio-based compound may be about 0.1 to 1 wt% based on the total weight of the lithium metal oxide particles.

In some embodiments, the cleaning liquid may be prepared by adding the thio-based compound to water. In one embodiment, the cleaning liquid may use an organic solvent, such as an alcohol solvent.

In some embodiments, a drying process may be further performed after the cleaning process. Through the drying process, the thio-coating may be fixed or stabilized on the particle surface.

<Lithium secondary battery>

According to exemplary embodiments, the lithium secondary battery may include a positive electrode, a negative electrode, and a separator including the lithium metal oxide particles having the thio-coating described above.

The positive electrode may include a positive electrode active material layer formed by applying a positive electrode active material including the lithium metal oxide particles to a positive electrode current collector.

For example, the slurry may be prepared by mixing and stirring the lithium metal oxide particles with a binder, a conductive material and / or a dispersant in a solvent. The slurry may be coated on the cathode current collector, and then compressed and dried to prepare a cathode.

The positive electrode current collector may include, for example, stainless steel, nickel, aluminum, titanium, copper, or an alloy thereof, and may preferably include aluminum or an aluminum alloy.

The binder is, for example, vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacryl Organic binders such as polymethylmethacrylate, or aqueous binders such as styrene-butadiene rubber (SBR), and may be used together with a thickener such as carboxymethyl cellulose (CMC).

For example, PVDF series binder can be used as a binder for positive electrode formation. In this case, the amount of the binder for forming the positive electrode active material layer may be reduced and the amount of the positive electrode active material may be relatively increased, thereby improving output and capacity of the secondary battery.

The conductive material may be included to promote electron transfer between active material particles. For example, perovskite (perovskite) material such as the conductive material is graphite, carbon black, graphene, carbon-based conductive material and / or tin oxide, tin oxide, titanium oxide, LaSrCoO _3, LaSrMnO _3, such as carbon nanotubes It may include a metal-based conductive material including a.

The negative electrode may include a negative electrode active material layer formed by coating a negative electrode current collector and a negative electrode active material on a negative electrode current collector.

The negative electrode active material may be used without particular limitation that is known in the art that can occlude and desorb lithium ions. For example, carbon-based materials, such as crystalline carbon, amorphous carbon, a carbon composite, carbon fiber; Lithium alloys; Silicon or tin and the like can be used. Examples of the amorphous carbon include hard carbon, coke, mesocarbon microbead (MCMB) fired at 1500 ° C. or lower, mesophase pitch-based carbon fiber (MPCF), and the like. Examples of the crystalline carbon include graphite-based carbon such as natural graphite, graphitized coke, graphitized MCMB, graphitized MPCF, and the like. Examples of the element included in the lithium alloy include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium or indium.

The negative electrode current collector may include, for example, gold, stainless steel, nickel, aluminum, titanium, copper, or an alloy thereof, and preferably may include copper or a copper alloy.

In some embodiments, a slurry may be prepared by mixing and stirring the negative electrode active material in a solvent, a binder, a conductive material and / or a dispersant, and the like. The slurry may be coated on the negative electrode current collector, and then compressed and dried to prepare the negative electrode.

As the binder and the conductive material, materials substantially the same as or similar to those described above may be used. In some embodiments, the binder for the formation of the negative electrode may include an aqueous binder such as styrene-butadiene rubber (SBR), for example, for compatibility with the carbon-based active material, such as carboxymethyl cellulose (CMC) Can be used with thickeners.

The separator may be interposed between the positive electrode and the negative electrode. The separator may include a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, ethylene / methacrylate copolymer, and the like. The separator may include a nonwoven fabric formed of high melting glass fibers, polyethylene terephthalate fibers, or the like.

In example embodiments, an electrode cell may be defined by the anode, the cathode, and the separator, and a plurality of the electrode cells may be stacked to form, for example, a jelly roll type electrode assembly. For example, the electrode assembly may be formed by winding, laminating, or folding the separator.

The electrode assembly may be accommodated together with an electrolyte in an outer case to define a lithium secondary battery. According to exemplary embodiments, a nonaqueous electrolyte may be used as the electrolyte.

The non-aqueous electrolyte comprising an electrolyte of a lithium salt and an organic solvent, wherein the lithium salt is for example Li ⁺ X ^- is represented by the lithium salt anion (X ^-) as F ^-, Cl ^-, Br ^-, I ^-, NO _{^{3 -, N (CN) 2}} -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4 PF 2 -, ( ^{_{CF 3) 5 PF -, (}} CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, (FSO 2) 2 N -, CF 3 CF ^{_{2 (CF 3) 2 CO -}} , (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2) 7 SO 3 -, CF 3 _{^{CO 2 -, CH 3 CO 2}} -, SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- and the like can be exemplified.

Examples of the organic solvent include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). ), Methylpropyl carbonate, dipropyl carbonate, dimethylsulfuroxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, tetrahydrofuran and the like can be used. . These may be used alone or in combination of two or more.

Electrode tabs may be formed from the positive electrode collector and the negative electrode collector belonging to each electrode cell, respectively, and may extend to one side of the outer case. The electrode tabs may be fused together with the one side of the outer case to form an electrode lead extending or exposed to the outside of the outer case.

The lithium secondary battery may be manufactured in, for example, a cylindrical shape, a square shape, a pouch type or a coin type using a can.

According to exemplary embodiments, the lithium secondary battery may be implemented by improving the chemical stability of the positive electrode active material by suppressing the capacity and the average voltage reduction by the thioamide coating, while improving the life and long-term stability.

Hereinafter, preferred examples are provided to aid the understanding of the present invention, but these examples are merely illustrative of the present invention and are not intended to limit the scope of the appended claims, which are within the scope and spirit of the present invention. It is apparent to those skilled in the art that various changes and modifications can be made to the present invention, and such modifications and changes belong to the appended claims.

Examples and Comparative Examples

In Examples and Comparative Examples, lithium metal oxides having a composition shown in Table 1 (Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ or Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ ), or Table 1 As described, lithium metal oxides with Al, Zr, Ti doping or Al ₂ O ₃ , ZrO ₂ , TiO ₂ coatings were used. Pure water (De-Ionized Water, DIW) having a specific resistance of less than 25 MΩcm was used in the washing process.

Examples

1 kg of pure water (deionized water, DIW) was placed in a 2L reactor and bubbled with nitrogen for 30 minutes to sufficiently remove dissolved oxygen inside the pure water. It was added to and stirred for 30 minutes. Then, after stirring at a speed of 300 rpm for 30 minutes in a nitrogen atmosphere with a lithium metal oxide of Table 1 as a positive electrode active material of 1 kg, it was filtered under reduced pressure using a Buchner funnel. The filtered lithium metal oxide was dried under vacuum at 200 to 300 degrees for 24 hours, and classified into 325mesh to obtain a final lithium metal oxide.

Comparative Examples

Substantially the same process as the examples was carried out except that no thio-based compound was used in the pure water as the washing liquid.

division Anode Composition Doping substance mol% Coating amount wt% Additive compound Added weight
(wt%) Al Zr Ti Al ₂ O ₃ ZrO ₂ TiO ₂ Example 1-1 Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ Dithiooxamide 0.5 Example 1-2 _{Li [Ni 0.88 Co 0.09 Mn 0.03} ] O 2 Sodium Dimethyldithiocarbanate Dihydrate 0.5 Example 1-3 Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ sodium 2-Thiobarbiturate 0.5 Example 1-4 _{Li [Ni 0.88 Co 0.09 Mn 0.03} ] O 2 thiosemicarbazide 0.5 Example 1-5 Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ thioacetamide 0.5 Example 1-6 _{Li [Ni 0.88 Co 0.09 Mn 0.03} ] O 2 N, N bis (carboxymethyl)
dithiooxamide 0.5 Example 1-7 _{Li [Ni 0.88 Co 0.09 Mn 0.03} ] O 2 Bis (carboxymethyl) trithiocarbonate 0.5 Example 1-8 Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ sodium thiosulfate 0.5 Example 2-1 Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ 0.3 0.2 0.2 Dithiooxamide 0.5 Example 2-2 _{Li [Ni 0.88 Co 0.09 Mn 0.03} ] O 2 0.3 0.2 0.2 Sodium Dimethyldithiocarbanate Dihydrate 0.5 Example 2-3 Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ 0.3 0.2 0.2 Bis (carboxymethyl) trithiocarbonate 0.5 Example 2-4 Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ 0.3 0.2 0.2 sodium thiosulfate 0.5 Example 3-1 Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ 0.5 0.06 0.2 Dithiooxamide 0.5 Example 3-2 Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ 0.5 0.06 0.2 Sodium Dimethyldithiocarbanate Dihydrate 0.5 Example 3-3 _{Li [Ni 0.88 Co 0.09 Mn 0.03} ] O 2 0.5 0.06 0.2 Bis (carboxymethyl) trithiocarbonate 0.5 Example 3-4 Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ 0.5 0.06 0.2 sodium thiosulfate 0.5 Example 4-1 Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ 0.5 0.06 0.2 Sodium Dimethyldithiocarbanate Dihydrate 2.0 Example 4-2 Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ 0.5 0.06 0.2 Sodium Dimethyldithiocarbanate Dihydrate 1.0 Example 4-3 Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ 0.5 0.06 0.2 Sodium Dimethyldithiocarbanate Dihydrate 0.25 Example 4-4 Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ 0.5 0.06 0.2 Sodium Dimethyldithiocarbanate Dihydrate 0.10 Example 4-5 Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ 0.5 0.06 0.2 Sodium Dimethyldithiocarbanate Dihydrate 0.05 Example 5-1 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ Dithiooxamide 0.5 Example 5-2 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ Sodium Dimethyldithiocarbanate Dihydrate 0.5 Example 5-3 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ Bis (carboxymethyl) trithiocarbonate 0.5 Example 5-4 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ sodium thiosulfate 0.5 Example 6-1 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ 0.3 0.2 0.2 Dithiooxamide 0.5 Example 6-2 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ 0.3 0.2 0.2 Sodium Dimethyldithiocarbanate Dihydrate 0.5 Example 6-3 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ 0.3 0.2 0.2 Bis (carboxymethyl) trithiocarbonate 0.5 Example 6-4 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ 0.3 0.2 0.2 sodium thiosulfate 0.5 Example 7-1 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ 0.5 0.06 0.2 Dithiooxamide 0.5 Example 7-2 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ 0.5 0.06 0.2 Sodium Dimethyldithiocarbanate Dihydrate 0.5 Example 7-3 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ 0.5 0.06 0.2 Bis (carboxymethyl) trithiocarbonate 0.5 Example 7-4 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ 0.5 0.06 0.2 sodium thiosulfate 0.5 Example 8-1 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ 0.5 0.06 0.2 Bis (carboxymethyl) trithiocarbonate 1.0 Example 8-2 _{Li [Ni 0.8 Co 0.1 Mn 0.1} ] O 2 0.5 0.06 0.2 Bis (carboxymethyl) trithiocarbonate 0.25 Example 8-3 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ 0.5 0.06 0.2 Bis (carboxymethyl) trithiocarbonate 0.10 Example 8-4 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ 0.5 0.06 0.2 Bis (carboxymethyl) trithiocarbonate 0.05 Example 9-1 _{Li [Ni 0.8 Co 0.1 Mn 0.1} ] O 2 0.5 0.06 0.2 sodium thiosulfate 1.0 Example 9-2 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ 0.5 0.06 0.2 sodium thiosulfate 0.25 Example 9-3 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ 0.5 0.06 0.2 sodium thiosulfate 0.10 Example 9-4 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ 0.5 0.06 0.2 sodium thiosulfate 0.05 Comparative Example 1 Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ none 0.0 Comparative Example 2 Li [Ni _0.88 Co _0.09 Mn _0.03 ] O ₂ 0.3 0.2 0.2 none 0.0 Comparative Example 3 _{Li [Ni 0.88 Co 0.09 Mn 0.03} ] O 2 0.5 0.06 0.2 none 0.0 Comparative Example 4 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ none 0.0 Comparative Example 5 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ 0.3 0.2 0.2 none 0.0 Comparative Example 6 Li [Ni _0.8 Co _0.1 Mn _0.1 ] O ₂ 0.5 0.06 0.2 none 0.0

Experimental Example

(1) Lithium salt impurity measurement

In a 250 mL flask, 5.0 g of lithium metal oxide particles of Examples and Comparative Examples were quantified, 100 g of deionized water was added thereto, a magnetic bar was added thereto, and the mixture was stirred at a speed of 4 rpm for 10 minutes. Thereafter, 50 g of an aliquot was collected after filtration using a vacuum flask. The aliquoted solution was placed in an auto titrator container and automatically titrated with 0.1 N HCl using the Wader Method to measure LiOH and Li ₂ CO ₃ values in the solution.

(2) battery characteristic evaluation

2-1) Secondary Battery Manufacturing

Each of the lithium metal oxide particles, carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder were mixed in a weight ratio of 92: 5: 3 to prepare the slurry. The slurry was uniformly applied to an aluminum foil having a thickness of 15 μm, and vacuum dried at 130 ° C. to prepare a positive electrode for a lithium secondary battery. The anode, a lithium foil as a counter electrode, a porous polyethylene membrane (thickness: 21 μm) as a separator to form an electrode assembly, and the electrode assembly in a solvent in which ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 3: 7. Using a liquid electrolyte in which LiPF ₆ was dissolved at a concentration of 1.0 M, a battery cell in the form of a coin half cell was prepared according to a commonly known manufacturing process, and evaluated at a voltage of 3.0 V to 4.3 V.

2-2) Initial charge and discharge measurement

The charge and discharge capacity of the battery cells according to the Examples and Comparative Examples was performed once by performing charge (CC / CV 0.1C 4.3V 0.05CA CUT-OFF) and discharge (CC 0.1C 3.0V CUT-OFF) once. Measured. (CC: constant current, CV: Constant voltage)

2-3) Initial Efficiency Measurement

The initial efficiency was measured by a percentage value obtained by dividing the initial discharge amount measured in 2-2) by the initial charge amount.

3) Capacity retention rate measurement

Discharge capacity at 300 times by repeating charge (CC / CV 0.5C 4.3V 0.05CA CUT-OFF) and discharge (CC 1.0C 3.0V CUT-OFF) 300 times for the battery cell according to the Examples and Comparative Examples The lifetime maintenance rate was evaluated as a percentage of the value divided by the discharge capacity at one time.

The measured values according to the experimental examples described above are shown in Table 2 below.

Example LiOH Li ₂ CO ₃ Initial charge Initial discharge amount Initial efficiency Lifetime @ 300 ^th wt% wt% mAh / g mAh / g % % Example 1-1 0.156 0.185 235 215 91 69 Example 1-2 0.176 0.190 235 214 91 71 Example 1-3 0.188 0.187 236 214 91 68 Example 1-4 0.153 0.179 234 215 92 70 Example 1-5 0.192 0.186 238 213 89 68 Example 1-6 0.169 0.201 237 215 91 72 Example 1-7 0.174 0.190 235 215 91 72 Example 1-8 0.163 0.208 236 215 91 71 Example 2-1 0.109 0.171 233 215 92 70 Example 2-2 0.099 0.199 235 215 91 75 Example 2-3 0.132 0.172 234 215 92 72 Example 2-4 0.172 0.197 233 214 92 70 Example 3-1 0.145 0.144 234 214 91 74 Example 3-2 0.193 0.172 236 214 91 76 Example 3-3 0.154 0.198 237 214 90 76 Example 3-4 0.176 0.186 238 213 89 75 Example 4-1 0.081 0.206 233 208 89 69 Example 4-2 0.105 0.193 234 210 90 75 Example 4-3 0.181 0.168 237 215 91 71 Example 4-4 0.185 0.180 240 215 90 70 Example 4-5 0.196 0.152 241 216 90 64 Example 5-1 0.195 0.131 227 202 89 69 Example 5-2 0.186 0.111 226 201 89 73 Example 5-3 0.189 0.123 225 201 89 72 Example 5-4 0.192 0.112 224 201 90 73 Example 6-1 0.108 0.182 224 200 89 71 Example 6-2 0.115 0.198 223 201 90 77 Example 6-3 0.157 0.178 223 199 89 76 Example 6-4 0.172 0.153 223 199 89 77 Example 7-1 0.149 0.190 221 200 90 77 Example 7-2 0.173 0.183 222 202 91 78 Example 7-3 0.155 0.188 225 200 89 79 Example 7-4 0.166 0.192 224 199 89 77 Example 8-1 0.170 0.198 222 198 89 77 Example 8-2 0.142 0.179 225 200 89 79 Example 8-3 0.138 0.171 225 199 88 76 Example 8-4 0.139 0.178 224 197 88 72 Example 9-1 0.189 0.202 222 198 89 76 Example 9-2 0.151 0.198 223 199 89 77 Example 9-3 0.138 0.204 223 198 89 73 Example 9-4 0.141 0.211 224 197 88 71 Comparative Example 1 0.121 0.192 243 211 87 28 Comparative Example 2 0.183 0.194 240 208 87 43 Comparative Example 3 0.211 0.256 240 211 87 45 Comparative Example 4 0.111 0.198 228 201 88 33 Comparative Example 5 0.167 0.188 225 197 88 49 Comparative Example 6 0.203 0.212 223 196 88 50

Referring to Table 2, when the cleaning including the thio-based compound described above is performed, the amount of lithium salt impurities is reduced, thereby obtaining excellent charge and discharge efficiency and capacity retention rate.

On the other hand, in Comparative Examples 1 to 6, in which the thioamide compound was not included, lithium salt impurities were not effectively removed, and the efficiency and capacity retention rate were remarkably lowered due to particle structure oxidation.

Claims (19)

Lithium metal oxide particles; And
A thio-based compound formed on at least a part of the lithium metal oxide particle surface and having a double bond containing a sulfur atom,
The thio-based compound includes a thiosulfate compound containing a thiosulfate ion represented by the following Structural Formula 3, and forms a coating layer, a ligand bond or a complex bond on the surface of the lithium metal oxide particles, a cathode active material for a lithium secondary battery :
[Formula 3]

.
delete delete delete delete delete The positive active material of claim 1, wherein the thiosulfate compound comprises at least one selected from the group consisting of salts represented by the following Chemical Formulas 22, 23, or 24:
[Formula 22] [Formula 23] [Formula 24]

.
The cathode active material according to claim 1, wherein the lithium metal oxide particles include lithium nickel-based metal oxides represented by the following general formula (1):
[Formula 1]
Li _x Ni _y M _y-1 O ₂
(In Formula 2, 0.95 <x <1.08, y ≧ 0.5, and M is at least one element selected from the group consisting of Co, Mn, Al, Zr, Ti, B, Mg, Ba).
The positive electrode active material for lithium secondary battery according to claim 8, wherein in formula (1), 0.8 ≦ y ≦ 0.93.
The positive electrode active material for lithium secondary battery of Claim 8 in which M contains Co and Mn in General formula 1.
The cathode active material of claim 8, wherein the lithium metal oxide particles include a doping or coating comprising at least one of Al, Zr, or Ti.
delete The positive electrode active material of claim 1, wherein the lithium metal oxide particles have a layered structure, and the thio-based compound coats a grain boundary of a surface portion of the lithium metal oxide particles.
Preparing lithium metal oxide particles; And
Washing the lithium metal oxide particles with a cleaning liquid containing a thio-based compound having a double bond containing a sulfur atom,
The thio-based compound includes a thiosulfate compound containing a thiosulfate ion represented by the following Structural Formula 3, and forms a coating layer, a ligand bond or a complex bond on the surface of the lithium metal oxide particles, a cathode active material for a lithium secondary battery Manufacturing method:
[Formula 3]

.
The method of claim 14, wherein the amount of the thio-based compound added is 0.05 to 2 wt% based on the total weight of the lithium metal oxide particles.
The method according to claim 14, wherein the amount of the thio-based compound added is 0.1 to 1% by weight based on the total weight of the lithium metal oxide particles.
The method of claim 14, further comprising mixing and heat treating the lithium metal oxide particles with at least one of Al ₂ O ₃ , ZrO _2, or TiO ₂ before the cleaning.
delete A positive electrode including lithium metal oxide particles and a positive electrode active material formed on at least a part of a surface of the lithium metal oxide particles and including a thio-based compound having a double bond containing a sulfur atom;
cathode; And
A separator disposed between the anode and the cathode,
The thio-based compound includes a thiosulfate compound comprising a thiosulfate ion represented by the following Structural Formula 3, and forms a coating layer, a ligand bond or a complex bond on the surface of the lithium metal oxide particles, a lithium secondary battery:
[Formula 3]

.