KR101858729B1 - Positive Electrode Mix Comprising Lithium Metal Sulfur Compound and Positive Electrode Prepared from the Same - Google Patents

Abstract

The present invention relates to a positive electrode active material and a positive electrode mixture for a secondary battery comprising the positive electrode additive and more particularly to a lithium metal sulfur compound positive electrode additive for compensating an irreversible capacity of the negative electrode active material in the activation process of the secondary battery And a positive electrode mixture for a secondary battery.

Description

[0001] The present invention relates to a positive electrode material mixture containing a lithium metal sulfur compound, and a positive electrode mixture prepared from the positive electrode material mixture,

The present invention relates to a positive electrode mixture for a secondary battery comprising a lithium metal sulfur compound as a positive electrode additive for compensating an irreversible capacity of an anode active material in the activation process of the secondary battery.

2. Description of the Related Art As technology development and demand for mobile devices such as portable computers, portable telephones, smart pads, and wearable devices have increased, the demand for secondary batteries as energy sources has been rapidly increasing, and the high energy density and operating potential A lithium secondary battery having a long cycle life and low self-discharge rate has been extensively studied, and it has been commercialized and widely used.

Such a lithium secondary battery has a structure in which an electrolyte including a lithium salt is impregnated in an electrode assembly having a porous separator interposed between a positive electrode and a negative electrode coated with an electrode active material on a current collector.

Lithium-containing cobalt oxide (LiCoO ₂ ) is mainly used as the positive electrode active material of the lithium secondary battery, and lithium-containing manganese oxide such as LiMn ₂ O _{4 having a} spinel crystal structure and lithium-containing nickel oxide (LiNiO ₂ ) are also used .

The theoretical specific capacity of pure silicon (Si) is 4200 mAh / g, and the specific surface area of graphite carbon is 372 mAh / g. Therefore, a lithium secondary battery using the Si-based active material attracts much attention, and some of the lithium secondary batteries are also used as an electrode mixed with a carbon material.

However, the Si-based active material as described above has a high irreversible capacity, which can negatively affect the capacity of the battery due to the consumption of lithium ions. Also, as the number of cycles increases, lithium ions are consumed, .

Therefore, when an electrode is manufactured using an active material having a high irreversible capacity, a pre-lithiation process should be included so that lithium can be inserted into the irreversible capacity portion. However, such a pre- There is a risk that there is a risk, a process is complicated, and an excessive cost is incurred.

Therefore, a need exists for a technique capable of solving such a problem.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

More particularly, the present invention relates to a lithium secondary battery comprising a lithium metal sulfur compound capable of directly compensating for the irreversible capacity of a negative electrode active material as a positive electrode additive, which is excellent in capacity characteristics and lifetime characteristics without a preliminary lithium ionization process, And to provide a secondary battery.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a cathode mixture for a secondary battery, comprising: a cathode active material; and a lithium metal sulfur compound as a cathode additive for compensating irreversible capacity of the anode active material during activation of the secondary battery.

That is, since the cathode mix for a secondary battery according to the present invention includes a lithium metal sulfur compound as a cathode additive, the irreversible capacity of the anode active material is compensated without a separate pre-lithization process. As a result, The manufacturing cost can be reduced.

Specifically, the lithium metal sulfur compound can compensate the irreversible capacity of the negative electrode active material by irreversible release of lithium in the initial charge / discharge process for activation of the secondary battery.

When the lithium secondary battery is charged, the lithium ion of the positive electrode active material is discharged and inserted into the carbon layer of the negative electrode. When discharged, lithium ions of the negative electrode carbon layer are discharged and inserted into the positive electrode active material, And serves as a medium for transferring lithium ions. Such a lithium secondary battery should basically be stable in the operating voltage range of the battery and have a capability of transferring ions at a sufficiently high speed.

However, in the continuous charging / discharging process, the electrolyte may be decomposed on the surface of the negative electrode active material and gas may be generated. In general, the lithium secondary battery forms an SEI film on the surface of the negative electrode active material during the initial charging / discharging process.

The positive electrode mixture according to the present invention includes a lithium metal sulfide compound capable of irreversibly releasing lithium in the initial charge / discharge process, so that the irreversible capacity of the negative electrode active material can be compensated without a separate preliminary lithium ionization process.

In one specific example, the lithium metal sulfur compound may have an operating voltage of 1.0 V to 2.5 V versus Li, and more specifically 1.1 V to 2.5 V, more specifically 1.2 V to 2.4 V .

Therefore, the lithium metal sulfur compound is lower than the operating voltage of the anode of 2.5V to 4.3V, so that it participates in the initial charge only, and does not participate in the discharge at the discharge, thereby reducing the irreversible capacity.

In the initial charging / discharging process, it is preferable to design the voltage within the above range so that only the lithium metal sulfur compound can participate in the reaction in the positive electrode mixture.

Such a lithium metal sulfur compound may be at least one selected from, for example, a lithium niobium sulfur compound and a lithium titanium sulfur compound.

That is, according to the present invention, the lithium niobium sulfur compound and the lithium titanium sulfur compound may be used singly as the lithium metal sulfur compound, or the lithium niobium sulfur compound and the lithium titanium sulfur compound may be used together.

In one specific example, the lithium niobium sulfur compound may be a compound represented by the following formula (1).

_{Li 3 + x Nb 1-y} M y S 4-z (1)

In this formula,

-0.1? X? 1, 0? Y? 0.5, -0.1? Z?

M is a metal of a +2 to +4 oxidation number or a transition metal cation.

The lithium niobium sulfur compound may be Li ₃ NbS ₄ in detail.

1 is a graph showing charge / discharge voltage curves of the lithium niobium sulfur compound.

As shown in FIG. 1, the lithium niobium sulfide compound has a flat region in the range of 1.8 V to 2.1 V, and has an operating voltage within the range, so that it can participate in a reaction in a state where a relatively low voltage is applied have.

In another specific example, the lithium titanium sulfur compound may be a compound represented by the following formula (2).

Li _{2 + x} Ti _1-y M ' _y S _{3 -z} (2)

In the above formula, -0.1? X? 1, 0? Y? 0.5, -0.1? Z?

M 'is a metal having a +2 to +4 oxidation number or a transition metal cation.

The lithium titanium sulfur compound may be specifically Li ₂ TiS ₃ .

FIG. 2 is a graph showing charge-discharge voltage curves of the lithium-titanium-sulfur compound.

Referring to FIG. 2, the lithium-titanium-sulfur compound has a flat region in the range of 1.5 to 2.3 V, and can participate in the reaction even when a voltage lower than 2.5 V is applied.

Therefore, when the voltage is maintained at 2.5 V or lower in the initial charging / discharging process, the lithium niobium sulfur compound and / or the lithium titanium sulfur compound contained in the positive electrode mixture participate in the charging reaction, while the positive electrode active material does not participate in the charging reaction Therefore, the irreversible capacity of the anode active material can be efficiently compensated during the charging / discharging process after the activation process, thereby omitting a separate pre-lithization process.

The lithium metal sulfide compound may be contained in an amount of 0.01 to 20% by weight, more specifically 0.02 to 10% by weight, and more preferably 0.05 to 5% by weight, based on the weight of the cathode active material May be included.

When the lithium metal-sulfur compound is contained in an amount less than 0.01% by weight, the desired effect may not be exhibited. On the contrary, when the content is more than 20% by weight, the overall capacity of the secondary battery may be lowered.

In the present invention, the cathode active material is not particularly limited as long as it is a material capable of intercalating and deintercalating lithium ions. It is preferable that the lithium transition metal oxide includes two or more transition metals, for example, lithium cobalt Layered compounds such as oxides (LiCoO ₂ ) and lithium nickel oxide (LiNiO ₂ ); A lithium nickel oxide, a spinel-based lithium nickel manganese composite oxide, a spinel-based lithium manganese oxide in which a part of Li is substituted with an alkaline earth metal ion, an olivine-based lithium metal phosphate, and the like But is not limited to these.

In one specific example, the cathode active material may be at least one selected from the compounds represented by the following general formulas (3) and (4).

Li _x M _y Mn _2-y O _{4 -z z} (3)

Li _{1 + a} Ni _b M ' _1-b O _{2 -c} A' _c (4)

Wherein M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti and Bi, A is at least one anion having a valence of -1 or -2;

M 'is at least one element selected from the group consisting of stable elements of 6 coordination such as Mn, Co, Mg and Al, and A' is at least one selected from the group consisting of -1 Or -2 one or more anions.

In one specific example, the positive electrode mixture may comprise a binder and a conductive material.

The conductive material is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, 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 and the like can be used.

The binder is a component which assists in bonding of the active material and the conductive material and bonding to the collector, and is usually added in an amount of 1 to 20% by weight based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

In some cases, a filler may be optionally contained as a component for suppressing the expansion of the positive electrode. Such a filler is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. For example, polyethylene, An olefin polymer such as polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

The present invention also provides a positive electrode in which the positive electrode mixture is applied on a positive electrode collector.

The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon, aluminum or stainless steel A surface treated with carbon, nickel, titanium, silver or the like may be used. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The method of applying the positive electrode mixture onto the current collector may include a method of uniformly dispersing the electrode mixture slurry on the current collector using a doctor blade or the like, a method of die casting, comma coating ), Screen printing, and the like. Alternatively, the electrode mixture slurry may be formed on a separate substrate and then bonded to the current collector by a pressing or lamination method, but the present invention is not limited thereto.

The mode of inclusion of the lithium metal sulfur compound in the cathode mixture is not particularly limited as long as lithium can be irreversibly released from the lithium metal sulfur compound, but may be dispersed in the cathode mixture in a state mixed with the cathode active material , A coating layer containing a separate lithium metal sulfur compound may be formed.

In one specific example, the lithium metal sulfur compound may be applied on the collector in admixture with the cathode active material.

In another specific example, a first coating layer including a cathode active material is coated on the current collector, and a coating layer containing a lithium metal sulfur compound may be coated on the first coating layer.

Specifically, the first coating layer is composed of a cathode active material, a conductive material and a binder, and the second coating layer is composed of a lithium metal-sulfur compound, a conductive material and a binder, and the lithium metal- It can be converted into an irreversible state in the activation process of the battery and act as a protective layer of the first coating layer.

That is, the second coating layer is thermally and electrochemically stable in the form of a metal sulfur compound in which lithium is exfoliated from the lithium metal sulfur compound. Thus, the first coating layer can be protected by suppressing side reactions of the electrode and the electrolyte.

The present invention also provides a secondary battery in which an electrolyte solution is impregnated in the electrode assembly including the positive electrode, the negative electrode, and the separator interposed between the positive electrode and the negative electrode.

The negative electrode active material may be carbon and graphite materials such as natural graphite, artificial graphite, expanded graphite, carbon fiber, hard graphitizable carbon, carbon black, carbon nanotube, fullerene and activated carbon; Silicon-based materials such as silicon, silicon oxide, and silicon-carbon based materials; _{Li x Fe 2 O 3 (0≤x≤1} ), Li x WO 2 (0≤x≤1), Sn x Me 1-x Me 'y O z (Me: Mn, Fe, Pb, Ge; Me' : Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, Halogen, 0 < x < Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, and Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials; Titanium oxide; Lithium titanium oxide, and the like, but the present invention is not limited thereto.

In one specific example, the negative electrode may include a silicon (Si) based material as the negative electrode active material, and the silicon based material may be a composite of silicon and silicon oxide and / or a silicon alloy.

The silicon-based material has a high irreversible capacity and is generally subjected to pre-lithization. However, the secondary battery according to the present invention does not require a separate pre-lithiation process because the positive electrode mixture contains a specific lithium metal sulfur compound .

When the negative electrode active material is further included, the other negative electrode active material may include 20 wt% to 80 wt% based on the total weight of the negative electrode active material. Such additional anode active materials may be selected from the materials exemplified above and, specifically, may be carbon-based materials.

The negative electrode current collector is generally made to have a thickness of 3 [mu] m to 500 [mu] m. Such an anode current collector is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples of the anode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, a surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.

The separation membrane is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 mu m, and the thickness is generally 5 to 300 mu m. Such separation membranes include, for example, olefinic polymers such as polypropylene, which are chemically resistant and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

The lithium salt-containing nonaqueous electrolyte is composed of a nonaqueous electrolyte and lithium. Nonaqueous organic solvents, organic solid electrolytes, inorganic solid electrolytes, and the like are used as the nonaqueous electrolyte, but the present invention is not limited thereto.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma -Butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane , Acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate Nonionic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyrophosphate, ethyl propionate and the like can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, A polymer containing an ionic dissociation group and the like may be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide.

The lithium salt-containing non-aqueous electrolyte may further contain, for the purpose of improving charge / discharge characteristics, flame retardancy, etc., for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. May be added. In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further added to impart nonflammability. In order to improve the high-temperature storage characteristics, carbon dioxide gas may be further added. FEC (Fluoro-Ethylene Carbonate, PRS (Propene sultone), and the like.

In one specific _{example, LiPF 6, LiClO 4, LiBF} 4, LiN (SO 2 CF 3) 2 , such as a lithium salt, a highly dielectric solvent of DEC, DMC or EMC Fig solvent cyclic carbonate and a low viscosity of the EC or PC of And then adding it to a mixed solvent of linear carbonate to prepare a lithium salt-containing non-aqueous electrolyte.

The secondary battery may be a lithium ion battery, a lithium ion polymer battery, or a lithium polymer battery.

The present invention also provides a battery pack including the secondary battery as a unit battery and a device including the battery pack as a power source.

The device may be selected from, but not limited to, a mobile phone, a notebook, a tablet PC, a wearable electronic device, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or a system for power storage.

The structures of these devices and their fabrication methods are well known in the art, and a detailed description thereof will be omitted herein.

As described above, the positive electrode material mixture for a secondary battery according to the present invention includes a lithium metal sulfur compound that irreversibly releases lithium in the initial charge-discharge process and compensates for the irreversible capacity of the negative electrode active material, And a safety layer is formed to improve safety.

1 is a graph showing charge-discharge voltage curves of a lithium niobium sulfur compound (Li ₃ NbS ₄ ).
FIG. 2 is a graph showing charge-discharge voltage curves of a lithium titanium sulfur compound (Li ₂ TiS ₃ ). FIG.

Manufacture of anode

≪ Example 1 >

A lithium niobium sulfide compound (Li ₃ NbS ₄ ) 1 ( ₃ % by weight) as a positive electrode active material, 93 wt% of a lithium nickel manganese cobalt composite oxide containing an excessive amount of nickel, 3 wt% of Super- (Nmethyl-2-pyrrolidone) as a solvent to prepare a positive electrode mixture. The positive electrode mixture was coated on an aluminum foil having a thickness of 15 占 퐉 to prepare a positive electrode.

≪ Example 2 >

94 wt% of lithium nickel manganese cobalt composite oxide containing excessive nickel as a positive electrode active material, 3 wt% of Super-P and 3 wt% of PVdF were added to NMP (N-methyl-2-pyrrolidone) And the positive electrode mixture was applied to an aluminum foil having a thickness of 15 탆 in a thickness of 1000 탆 to form a first coating layer. Then, a coating material was prepared by adding 94 wt% of lithium niobium sulfur compound (Li ₃ NbS ₄ ), 3 wt% of Super-P and 3 wt% of PVdF to the solvent NMP to form a coating having a thickness of 10 μm To prepare a positive electrode.

≪ Example 3 >

92 wt% of lithium nickel manganese cobalt composite oxide containing excessive nickel as a positive electrode active material, 3 wt% of Super-P, 3 wt% of PVdF and 2 wt% of lithium titanium sulfide (Li ₂ TiS ₃ ) Nmethyl-2-pyrrolidone) to prepare a positive electrode mixture. The positive electrode mixture was coated on an aluminum foil having a thickness of 15 탆 to prepare a positive electrode.

<Example 4>

94 wt% of lithium nickel manganese cobalt composite oxide containing excessive nickel as a positive electrode active material, 3 wt% of Super-P and 3 wt% of PVdF were added to NMP (N-methyl-2-pyrrolidone) The positive electrode material mixture was applied to an aluminum foil having a thickness of 15 탆 in a thickness of 990 탆 to form a first coating layer. Then, a coating material was prepared by adding 94 wt% of a lithium-titanium-sulfur compound (Li ₂ TiS ₃ ), 3 wt% of Super-P and 3 wt% of PVdF to a solvent NMP to form a 20 μm thick To prepare a positive electrode.

&Lt; Comparative Example 1 &

94 wt% of a lithium nickel manganese cobalt composite oxide containing excessive nickel as a positive electrode active material, 3 wt% of Super-P and 3 wt% of PVdF, except that a lithium niobium sulfur compound (Li ₃ NbS ₄ ) Was added to NMP as a solvent, and a positive electrode was prepared in the same manner as in Example 1.

Manufacture of batteries

The negative electrode prepared in Examples 1 to 4 and Comparative Example 1 and the negative electrode comprising the silicon-carbon composite as the negative electrode active material were each composed of a negative electrode having an irreversible efficiency of 84% (charge capacity 535 mAh / g) An electrode assembly was prepared using a porous separator. Thereafter, the electrode assembly was placed in a pouch and lead wires were connected. Thereafter, a 1: 1: 1 volume ratio of 1 M LiPF ₆ salt dissolved in ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate ) Was injected into the electrolyte, and then sealed to form a lithium secondary battery of the type.

<Experimental Example 1>

The irreversible efficiency of the positive electrode prepared in each of Examples 1 to 4 and Comparative Example 1 and the capacity of the battery including the positive electrode and the negative electrode were measured and are shown in Table 1, respectively.

Cathode efficiency (%) Anode efficiency (%) Example 1 84 86 Example 2 84 87 Example 3 84 85 Example 4 84 88 Comparative Example 1 84 93

As shown in Table 1, Examples 1 to 4 of the present invention show that a battery containing a lithium niobium sulfide compound or a lithium titanium sulfur compound and containing a positive electrode mixture of Comparative Example 1 containing no lithium metal sulfur compound It can be confirmed that the irreversible efficiency difference with the cathode is small. This is due to irreversible release of lithium ions in the lithium metal sulfur compound to increase the irreversible area of the positive electrode, which can improve the capacity of the battery as a whole.

The irreversible release of the lithium metal sulfur compounds proceeds only during the initial activation process because the working voltage of the lithium metal is in the range of 1.0 V to 2.5 V relative to Li and is lower than the working voltage of the anode, It participates in the reaction only at the time of charging, and does not participate in the reaction at the time of discharge.

Accordingly, when the lithium niobium sulfide compound or lithium titanium oxide is added to the positive electrode mixture or further coated on the positive electrode mixture layer, the irreversible portion of the negative electrode is compensated to increase the overall capacity of the battery cell and the cycle life is improved .

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (22)

The positive electrode active material,
As a positive electrode additive for compensating an irreversible capacity of an anode active material in the activation process of a secondary battery, Li ₃ NbS ₄ which is a lithium niobium sulfur compound; And Li ₂ TiS ₃ , which is a lithium-titanium-sulfur compound, based on the total weight of the positive electrode mixture. The positive electrode material mixture according to claim 1, wherein the lithium metal sulfur compound compensates the irreversible capacity of the negative electrode active material by irreversible discharge of lithium in an initial charge / discharge process for activating the secondary battery. The positive electrode material mixture according to claim 1, wherein the lithium metal sulfur compound has an operating voltage of 1.0 V to 2.5 V relative to Li. delete delete delete delete delete [3] The positive electrode material mixture according to claim 1, wherein the lithium metal sulfur compound is contained in an amount of 0.01 to 20% by weight based on the weight of the positive electrode active material. The positive electrode material mixture according to claim 1, wherein the positive electrode active material is at least one selected from the compounds represented by the following formulas (3) and (4)
Li _x M _y Mn _2-y O _{4 -z z} (3)
Li _{1 + a} Ni _b M ' _1-b O _{2 -c} A' _c (4)
Wherein M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti and Bi, A is at least one anion having a valence of -1 or -2;
M 'is at least one element selected from the group consisting of stable elements of 6 coordination such as Mn, Co, Mg and Al, and A' is at least one selected from the group consisting of -1 Or -2 one or more anions. The positive electrode material mixture according to claim 1, wherein the positive electrode material mixture contains a binder and a conductive material. A positive electrode, characterized in that the positive electrode mixture according to any one of claims 1 to 3 and 9 to 11 is applied on a current collector. 13. The anode according to claim 12, wherein the lithium metal sulfur compound is applied on the collector in a state mixed with the cathode active material. 13. The anode according to claim 12, wherein a first coating layer including a cathode active material is coated on the current collector, and a second coating layer containing lithium metal sulfur compound is coated on the first coating layer. 15. The anode according to claim 14, wherein the first coating layer is composed of a cathode active material, a conductive material and a binder, and the second coating layer is composed of a lithium metal sulfur compound, a conductive material and a binder. 15. The anode according to claim 14, wherein the lithium metal sulfur compound of the second coating layer is converted into an irreversible state during the activation of the secondary battery and acts as a protective layer of the first coating layer. An electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode according to claim 12, wherein an electrolyte solution is impregnated into the electrode assembly. The secondary battery according to claim 17, wherein the negative electrode comprises a silicon (Si) based material as a negative electrode active material. The secondary battery according to claim 18, wherein the silicon-based material is silicon, silicon oxide, or a silicon alloy. The secondary battery according to claim 18, wherein the negative electrode active material further comprises a carbonaceous material, and the carbonaceous material is contained in an amount of 20 to 80 wt% based on the total weight of the negative electrode active material. A battery pack comprising a secondary battery according to claim 17 as a unit cell. The device according to claim 21, comprising the battery pack as a power source.

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