WO2019004731A1 - Cathode for lithium secondary battery and lithium secondary battery comprising same - Google Patents

Abstract

The present invention provides a cathode and a lithium secondary battery, the cathode comprising: a nickel-containing cathode active material having a large energy capacity; and an additive comprising metal particles and a lithium oxide.

Description

Lithium secondary battery anode and lithium secondary battery comprising same

Mutual citation with related application

This application claims the benefit of priority based on Korean Patent Application No. 2017-0081273, filed on June 27, 2017, and Korean Patent Application No. 2018-0074359, filed on June 27, 2018, all of which are incorporated herein by reference in their entirety The contents of which are incorporated herein by reference.

Technical field

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

As technology development and demand for mobile devices have increased, there has been a rapid increase in demand for secondary batteries as energy sources. Among such secondary batteries, lithium secondary batteries, which exhibit high energy density and operating potential, long cycle life, Batteries have been commercialized and widely used.

The lithium secondary battery generally comprises a positive electrode containing a positive electrode active material, a negative electrode including a negative electrode active material, a separator and an electrolyte, and is charged and discharged by intercalation-decalation of lithium ions. The lithium secondary battery has a high energy density, a large electromotive force, and a high capacity, so it is applied to various fields.

Various methods have been studied to realize higher capacity of such lithium secondary batteries. Specifically, a method of realizing a high capacity of a lithium secondary battery by using one or more materials such as LCO, LNMCO, and LMO as a cathode active material contained in a cathode for a lithium secondary battery has been attempted. However, in order to increase the capacity of an actual lithium secondary battery, not only the capacity of the positive electrode but also the capacity of the negative electrode should be improved. To this end, a method of using a silicon-based negative active material as a negative electrode has also been attempted. However, in the case of such a silicon-based negative electrode active material, irreversible capacity is also large, resulting in a problem of low charging / discharging efficiency. In order to solve the irreversible capacity problem while using such a silicon-based negative active material, the silicon-based active material must be lithiated, which poses a problem of high cost in lithization.

Accordingly, there is a demand for development of a lithium secondary battery which is high in capacity, exhibits excellent charge / discharge efficiency and can be manufactured at low cost.

In order to solve the above-mentioned problems, a first technical object of the present invention is to provide an anode capable of achieving high capacity and excellent initial capacity of a secondary battery by including an additive.

A second technical object of the present invention is to provide a lithium secondary battery including the positive electrode, which is excellent in charge / discharge efficiency and has a high capacity, and can be manufactured at low cost without a separate lithization process.

A third object of the present invention is to provide a positive electrode additive capable of achieving an excellent initial capacity of a secondary battery by including metal particles and lithium oxide.

In one embodiment of the present invention, a nickel-containing positive electrode active material; And an additive comprising metal particles and lithium oxide.

The present invention also provides a lithium secondary battery including the positive electrode, the negative electrode, and a separator interposed between the positive electrode and the negative electrode.

Also provided is a positive electrode additive comprising metal particles and lithium oxide.

According to the present invention, the metal particles contained in the additive and the lithium oxide react with each other at a driving voltage (2.5 V to 4.3 V) of the lithium secondary battery by including the metal particles and the additive including lithium oxide in the production of the anode, A metal oxide is formed, and lithium ions migrate to the negative electrode to lithiate the negative electrode active material. As a result, it is not necessary to further perform a separate lithiation process, and thus a lithium secondary battery exhibiting excellent capacity at a low cost can be manufactured.

In addition, the metal oxide produced by the reaction of the metal particles and the lithium oxide to adsorb the gas such as CO or CO _2, may be a cell prevent reliability degradation due to CO or CO ₂ gas generated during charging and discharging, Swelling can also be reduced.

Fig. 1 is a diagram showing the charging capacities of the test secondary batteries 1 to 3 including Production Examples 1 and 2 and Comparative Production Example 1. Fig.

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

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

anode

A positive electrode according to an embodiment of the present invention includes a nickel-containing positive electrode active material; And additives comprising metal particles and lithium oxides.

Specifically, the positive electrode is formed by stacking a nickel-containing positive electrode active material on a positive electrode collector; And an additive comprising metal particles and lithium oxide.

The positive electrode collector is not particularly limited as long as it has electrical conductivity without causing chemical change in the battery. For example, the positive electrode collector may be formed of a metal such as carbon, stainless steel, aluminum, nickel, titanium, sintered carbon, , Nickel, titanium, silver, or the like may be used.

The metal particles included in the additive may preferably include at least one or more selected from the group consisting of Fe, Co, Cr, Mn, and Ni. In particular, when at least one metal particle selected from the above is included, it is possible to form a nano-sized composite having a capacity about four times larger than that of the existing lithium transition metal oxide, and the composite has a large charge / discharge voltage hysteresis curve So that the initial charge / discharge efficiency can be improved by adding a positive electrode additive.

In addition, the lithium oxide included in the additive may include at least one or more selected from the group consisting of Li ₂ O, Li ₂ O ₂ , and LiO ₂ .

Wherein the composition for forming an anode contains the metal particles and the additive including the lithium oxide so that the metal particles and the lithium oxide contained in the additive cause an electrochemical reaction in the drive voltage range of the additive, . ≪ / RTI > When the additive forms a lithium ion and a metal oxide, when the additive is applied to a secondary battery, the lithium ion moves to the cathode according to charging / discharging of the secondary battery, thereby further increasing the capacity of the battery. It is possible to adsorb a gas such as CO or CO ₂ which may be generated during charging and discharging, thereby reducing the swelling phenomenon.

The average particle diameter (D ₅₀ ) of the metal particles may be 5 μm or less, preferably 1 nm to 5 μm, 1 nm to 1 μm, and more preferably 10 nm to 50 nm. When the metal particles have a particle diameter of more than 5 mu m, the reaction with lithium oxide may hardly occur. The smaller the average particle size of the particles, the better the reaction with lithium oxide is, Can be further improved.

The average particle diameter (D ₅₀ ) of the metal particles can be defined as a particle diameter corresponding to 50% of the volume accumulation amount in the particle diameter distribution curve of the particles. For example, the average particle diameter (D ₅₀ ) of the metal particles can be measured using a laser diffraction method. The laser diffraction method generally enables measurement of a particle diameter from a submicron region to several millimeters, resulting in high reproducibility and high degradability. For example, the average particle diameter (D ₅₀ ) of the metal particles is measured by introducing the metal particles into a commercially available laser diffraction particle size analyzer (for example, Microtrac MT 3000) to measure an ultrasonic wave of about 28 kHz at an output of 60 W After irradiation, the average particle diameter (D ₅₀ ) at a 50% reference of the particle diameter distribution in the measuring apparatus can be calculated.

For example, the additive may include metal particles and lithium oxide in a ratio of 1: 0.1 to 1: 4, preferably 1: 0.3 to 1: 4, more preferably 1: 0.3 to 1: 3, 0.5 to 1: 2 in terms of molar ratio. When the metal particles and the lithium oxide are included in the above range, the metal particles and the lithium oxide included in the additive are electrochemically reacted in the drive voltage range of the additive to easily form lithium ions and metal oxides, The capacity of the secondary battery can be further improved. For example, when the metal particles and the lithium oxide are contained in an amount of less than 1: 0.1, since the amount of lithium oxide that the metal can react with is small, a metal oxide can not be formed with lithium ions, . Therefore, capacity may be smaller than that of lithium metal used as a conventional anode. On the contrary, when the metal particles and the lithium oxide are more than 1: 4, the amount of lithium oxide to be reacted is small and the capacity may hardly be obtained.

On the other hand, the nickel-containing cathode active material contained in the composition for forming an anode may be LiNiO ₂ , Li _{1 + w} (Ni _{1- xy z} Co _x M _{y y} M2 _z ) O ₂ , Fe, Mn, V, Cr, Ti, W, Ta, Mg and Mo and 0? W? 1, 0? X <1, 0? Y <1, 0? Z <1 Mn, V, Cr, Ti, W, Ta, Mg, and Mo), Li _{1 + w 1} Ni _a Co _b M1 _c O ₂ 1, 0? C <1, a + b + c = 1), and combinations thereof. can do. Specifically, the nickel-containing cathode active material may preferably contain a high content of nickel at 60 mol% or more, relative to the total number of moles of the transition metal oxide contained in the nickel-containing cathode active material. More specifically, the nickel-containing cathode active material is LiNi _{0. 8} Co _{0 . 1} Mn _{0 . 1} O ₂ or LiNi _{0 . 6} Co _{0 . 2} Mn _{0 . 2} O ₂ , but it is not limited thereto.

The nickel-containing positive electrode active material may be contained in an amount of 1 to 99 parts by weight, preferably 30 to 99 parts by weight, more preferably 50 to 99 parts by weight based on the total weight of the positive electrode.

The amount of the additive included in the composition for forming an anode may be controlled according to the irreversible capacity of the negative electrode. For example, the additive may be added in an amount of 0.1 to 100 parts by weight, preferably 1 to 50 parts by weight, 1 to 10 parts by weight, and most preferably 3 to 7 parts by weight based on the total weight of the composition for forming an anode . For example, when the additive is contained in an amount of less than 0.1 part by weight based on the total weight of the composition for forming an anode, it is difficult to achieve the effect of generating lithium ions by the addition of the additive, thereby increasing the capacity and secondary capacity of the secondary battery. .

In addition, the anode may further include a conductive material and a binder.

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% by weight to 30% by weight based on the total solid content of the composition for forming an anode. 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-butadiene rubber, fluorine rubber, various copolymers and the like.

The conductive material is usually added in an amount of 1 wt% to 30 wt% based on the total solid weight of the composition for forming an anode.

Such a conductive material is not particularly limited as long as it has electrical conductivity without causing a chemical change in the battery, and includes, for example, graphite; Carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal 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. Concrete examples of commercially available conductive materials include acetylene black series such as Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company, etc.), Ketjenblack, EC (Armak Company), Vulcan XC-72 (Cabot Company), and Super P (Timcal).

On the other hand, the positive electrode can be produced by a conventional positive electrode manufacturing method, except that the above-mentioned composition for forming an anode is used. Specifically, the composition for forming an anode can be coated on the positive electrode current collector, followed by drying and rolling.

Alternatively, the positive electrode may be produced by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating a film obtained by peeling from the support onto the positive electrode collector.

Secondary battery

Further, the present invention provides a lithium secondary battery comprising the above-described positive electrode, negative electrode, and separator interposed between the positive electrode and the negative electrode.

The lithium secondary battery includes a positive electrode, a negative electrode disposed opposite to the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. The lithium secondary battery may further include a battery container for housing the electrode assembly of the anode, the cathode, and the separator, and a sealing member for sealing the battery container.

Since the anode is the same as that described above, a detailed description thereof will be omitted, and only the remaining constitution will be specifically described below.

The negative electrode may be prepared by coating a negative electrode current collector with a negative electrode composition containing a silicon-based negative active material, a binder, a conductive material, a solvent, and the like.

For example, the silicon-based anode active material may include at least one selected from the group consisting of Si and SiO _x (0 <x? 2).

In addition, the negative electrode may further include a compound capable of reversibly intercalating and deintercalating lithium, in addition to the silicon-based negative active material. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber and amorphous carbon; Metal compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys or Al alloys; _{SiO β (0 <β <2} ), SnO 2, vanadium oxide, which can dope and de-dope a lithium metal oxide such as lithium vanadium oxide; Or a composite containing the above-described metallic compound and a carbonaceous material such as a Si-C composite or a Sn-C composite, and any one or a mixture of two or more thereof may be used. Also, a metal lithium thin film may be used as the negative electrode active material. As the carbon material, both low crystalline carbon and highly crystalline carbon may be used. Examples of the low-crystalline carbon include soft carbon and hard carbon. Examples of the highly crystalline carbon include natural graphite, artificial graphite, artificial graphite or artificial graphite, Kish graphite graphite, pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar coke derived cokes).

Preferably, the negative electrode may include a silicon-based negative active material having a high irreversible capacity and a carbon-based negative active material.

The negative electrode active material may be contained in an amount of 1 wt% to 99 wt%, preferably 50 wt% to 99 wt%, and more preferably 80 wt% to 99 wt% based on the total solid content of the composition for forming a negative electrode.

The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Examples of the negative electrode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver or the like, aluminum-cadmium alloy, or the like can be used. In addition, the negative electrode collector may have a thickness of 3 to 500 탆, and similarly to the positive electrode collector, fine unevenness may be formed on the surface of the collector to enhance the binding force of the negative electrode active material. For example, the negative electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The binder is a component for assisting the bonding between the conductive material, the active material and the current collector, and is usually 1% by weight to 30% by weight, preferably 1% by weight to 20% by weight, based on the total solid content of the composition for forming a negative electrode . Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene Examples thereof include ethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluorine rubber and various copolymers thereof.

The conductive material may be added in an amount of 1% by weight to 20% by weight, preferably 1% by weight to 10% by weight, based on the total solid content of the negative electrode composition, as a component for further improving the conductivity of the negative electrode 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 acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal 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 solvent may include water or an organic solvent such as N-methyl-2-pyrrolidone (NMP), and may be used in an amount that makes it desirable to contain the negative electrode active material, and optionally, a binder and a conductive material . For example, the concentration of the solid material including the negative electrode active material, and optionally the binder and the conductive material may be 50 wt% to 95 wt%, preferably 70 wt% to 90 wt%.

When the anode including the silicon-based anode active material is used, high capacity can be achieved when it is dedicated to the battery, but the energy density of the secondary battery is rather low due to the high irreversible capacity of the silicon-based anode active material.

Thus, by including the positive electrode including the above-described metal particles and the additive including lithium oxide in addition to the negative electrode including the silicon-based negative active material, the metal particles included in the positive electrode and the lithium As the lithium ions generated by the reaction of the oxides move to the cathode, the irreversible capacity of the cathode can be lowered by lithiating the cathode.

Specifically, when the driving voltage of a general battery is 2.5 V to 4.3 V and the driving voltage of the cathode active material contained in the anode is out of the driving voltage range of the battery, the cathode active material does not participate in the electrochemical reaction.

In one embodiment, the driving voltage of the cathode active material is 2.5 V to 4.3 V, and the driving voltage of the additive is less than 2.5 V, specifically, 0.5 V to 2.5 V.

The driving voltage means a voltage at which lithium ions are desorbed when a voltage is applied, and may preferably mean a voltage at which desorbed lithium ions migrate to the cathode.

That is, when the battery is charged to less than 2.5 V which is less than the driving voltage range of the positive electrode active material, the electrochemical reaction of the positive electrode active material does not occur, and the metal particles and the lithium oxide included in the composition for forming the positive electrode are electrochemically reacted do. That is, the metal particles contained in the positive electrode and the additive including the lithium oxide react with each other at less than the drive voltage range of the positive electrode active material (less than 2.5 V) to form lithium ions and metal oxides, As the lithium ions enter the negative electrode active material to lithiate the negative electrode, the irreversible capacity of the negative electrode decreases.

In addition, due to the metal oxide formed after the reaction, gas such as CO or CO ₂ that may occur during the charging / discharging process is adsorbed, and the swelling phenomenon of the battery can be reduced.

Specifically, when using the Fe particles and Li ₂ O as the additive contained in the composition for a positive electrode formed, 2.5 V less than Fe particle and a Li ₂ O is causing the electrochemical reaction represented by the following general formula (1) to (3) .

2Fe + 3Li ₂ O? Li ₂ Fe ₂ O ₃ + 4Li ⁺ + 4e ^- (1)

Li ₂ Fe ₂ O ₃ ? - Li ₂ Fe ₂ O ₃ + Li ⁺ + e ^- (2)

? - Li ₂ Fe ₂ O ₃ ? Fe ₂ O ₃ + Li ⁺ + e ^- (3)

At this time, finally produced Fe ₂ O ₃ remains on the anode to adsorb the gas that may occur during the charging / discharging process to reduce the swelling phenomenon of the battery, and lithium ions move to the cathode to lithium ionize the cathode.

According to the above-described reaction, the negative electrode may reduce the irreversible capacity of the negative electrode even if a separate lithiation process is not performed, and as a result, it is possible to achieve an effect of increasing the capacity and capacity of the secondary battery.

As the separator included in the secondary battery, a conventional porous polymer film conventionally used as a separator, such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / A porous polymer film made of a polyolefin-based polymer such as a polyolefin-based polymer can be used alone or in a laminated state or a nonwoven fabric made of a conventional porous nonwoven fabric such as a glass fiber having a high melting point or a polyethylene terephthalate fiber can be used But is not limited thereto.

At this time, an organic / inorganic composite membrane having an additional inorganic coating may be used for securing heat resistance or mechanical strength, and may be selectively used as a single layer or a multi-layer structure.

The inorganic material is not particularly limited as long as it can control the pores of the organic / inorganic composite separation membrane uniformly and improve the heat resistance. For example, the inorganic material is a non-limiting example is _{SiO 2, Al 2 O 3,} TiO 2, BaTiO 3, Li 2 O, LiF, LiOH, Li 3 N, BaO, Na 2 O, Li 2 CO 3, CaCO 3, At least one selected from the group consisting of LiAlO ₂ , SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , SiC and their derivatives and mixtures thereof.

The average diameter of the inorganic material may be 0.001 탆 to 10 탆, and more specifically 0.001 탆 to 1 탆. If the average diameter of the inorganic materials is within the above range, the dispersibility in the coating solution is improved and the occurrence of problems in the coating process can be minimized. In addition, the physical properties of the final separation membrane can be made uniform, the inorganic particles can be uniformly distributed in the pores of the nonwoven fabric to improve the mechanical properties of the nonwoven fabric, and the advantage of easily controlling the pore size of the organic- .

The average diameter of the pores of the organic / inorganic hybrid separator may be in the range of 0.001 to 10 mu m, more specifically 0.001 to 1 mu m. When the average diameter of the pores of the organic / inorganic hybrid separator is within the above range, gas permeability and ion conductivity can be controlled within a desired range. In addition, when the battery is manufactured using the organic / inorganic hybrid separator, It is possible to eliminate the possibility of an internal short circuit of the battery by the battery.

The porosity of the organic / inorganic hybrid membrane may range from 30% by volume to 90% by volume. When the porosity is within the above range, the ion conductivity can be increased and the mechanical strength can be enhanced.

Examples of the electrolyte used in the present invention include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, and a molten inorganic electrolyte that can be used in the production of a lithium secondary battery. It is not.

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

The organic solvent may be used without limitation as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate,? -Butyrolactone and? -Caprolactone; Ether solvents such as dibutyl ether or tetrahydrofuran; Ketone solvents such as cyclohexanone; Aromatic hydrocarbon solvents such as benzene and fluorobenzene; Dimethyl carbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate PC) and the like; Alcohol solvents such as ethyl alcohol and isopropyl alcohol; R-CN (R is a linear, branched or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double bond aromatic ring or an ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; Or sulfolane may be used. Among these, a carbonate-based solvent is preferable, and a cyclic carbonate (for example, ethylene carbonate or propylene carbonate) having a high ionic conductivity and a high dielectric constant, for example, such as ethylene carbonate or propylene carbonate, For example, ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) is more preferable. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1: 1 to about 1: 9, the performance of the electrolytic solution may be excellent.

The lithium salt can 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, 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 may be used. The concentration of the lithium salt is preferably in the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has an appropriate conductivity and viscosity, so that it can exhibit excellent electrolyte performance and the lithium ion can effectively move.

In addition to the electrolyte components, the electrolyte may contain, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate or the like, pyridine, triethanolamine, or the like for the purpose of improving lifetime characteristics of the battery, Ethyl phosphite, triethanol amine, cyclic ether, ethylenediamine, glyme, hexametriamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, At least one additive such as benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, The additive may be included in an amount of 0.1 to 5% by weight based on the total weight of the electrolyte.

As described above, since the lithium secondary battery including the cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, it can be used in portable devices such as mobile phones, notebook computers, digital cameras, and hybrid electric vehicles hybrid electric vehicle (HEV)).

According to another embodiment of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell and a battery pack including the same.

The battery module or the battery pack may include a power tool; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); Or a power storage system, as shown in FIG.

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, a coin shape, or the like using a can.

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

Hereinafter, the present invention will be described in detail by way of examples with reference to the following examples. However, the embodiments according to the present invention can be modified into 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 enable those skilled in the art to more fully understand the present invention.

Example

Manufacturing example  One

Fe having an average particle diameter of 50 nm and Li ₂ O powder were mixed at a molar ratio of 1: 1.5 to prepare an irreversible anode additive.

Manufacturing example  2

Fe having an average particle diameter of 5 탆 and Li ₂ O powder were mixed at a molar ratio of 1: 1.5 to prepare an irreversible anode additive.

compare Manufacturing example  One

An irreversible anode additive was prepared using 100% Li ₂ O powder.

Example  One

(Anode manufacture)

LiNi _{0 . 8} Mn _{0 . 1} Co _{0 .} 97.5 parts by weight of ₁ O ₂ cathode active material, 1 part by weight of FX35 of Denka as a conductive material, and 1.5 parts by weight of DA288 (KUREHA Corporation) as a binder were mixed in a solvent, 1 part by weight of an irreversible positive electrode additive were mixed in a solvent to prepare a composition for forming a positive electrode. This was applied to a positive electrode current collector (Al thin film) having a thickness of 20 μm at a loading amount of 6 mAh / cm ² , dried, and roll pressed to prepare a positive electrode.

(Cathode manufacture)

94.2 parts by weight of a mixed anode active material obtained by mixing graphite anode active material and SiO2 anode active material in a ratio of 70:30, 2.5 parts by weight of A544 (ZEON) as a binder, 2 parts by weight of Super C65 (Timcal) as a conductive material, 2000 (Daicel Co.), and the mixture was added to water as a solvent to prepare a composition for forming an anode. The negative electrode composition was coated on a negative electrode current collector (Cu thin film) having a thickness of 20 탆, dried, and roll pressed to prepare a negative electrode.

(Secondary Battery Manufacturing)

The positive electrode and the negative electrode prepared by the above-described method were laminated together with a separator to produce an electrode assembly. The electrode assembly was inserted into a battery case, and an electrolyte solution was injected and sealed to prepare a lithium secondary battery.

Example  2

A positive electrode, a negative electrode and a secondary battery including the same were prepared in the same manner as in Example 1, except that 2 parts by weight of the irreversible positive electrode additive prepared in Preparation Example 1 was used.

Example  3

A positive electrode, a negative electrode and a secondary battery comprising the same were prepared in the same manner as in Example 1, except that 3 parts by weight of the irreversible positive electrode additive prepared in Preparation Example 1 was used.

Example  4

A positive electrode, a negative electrode and a secondary battery comprising the same were prepared in the same manner as in Example 1, except that 4 parts by weight of the irreversible positive electrode additive prepared in Preparation Example 1 was used.

Example  5

A positive electrode, a negative electrode and a secondary battery comprising the same were prepared in the same manner as in Example 1, except that 5 parts by weight of the irreversible positive electrode additive prepared in Preparation Example 1 was used.

Example  6

A positive electrode, a negative electrode and a secondary battery comprising the same were prepared in the same manner as in Example 1, except that 6 parts by weight of the irreversible positive electrode additive prepared in Preparation Example 1 was used.

Example  7

A positive electrode, a negative electrode, and a secondary battery including the same were prepared in the same manner as in Example 1, except that 7 parts by weight of the irreversible positive electrode additive prepared in Preparation Example 1 was used.

Comparative Example  One

A positive electrode, a negative electrode and a secondary battery including the positive electrode and the negative electrode were prepared in the same manner as in Example 1, except that the additive was not included in the composition for forming the positive electrode.

Experimental Example  One: Irreversible  Identification of irreversibility of additive

Irreversible additive compositions 1 to 3 were prepared by mixing the irreversible positive electrode additive prepared in Preparation Examples 1 and 2 and Comparative Preparation Example 1, the conductive material and the binder in a solvent in a weight ratio of 80:10:10. The positive electrode current collector was coated on the positive electrode current collector, followed by drying and roll pressing to obtain test negative electrodes 1 and 2 and comparative test for confirming the irreversibility of the irreversible additives prepared in Preparation Examples 1 and 2 and Comparative Preparation Example 1 Respectively. Here, the same materials as in Example 1 were used for the conductive material, the binder, and the solvent, respectively.

The negative electrode and the test secondary batteries 1 to 3 including the same were prepared in the same manner as in Example 1 except that the test positive electrodes 1 and 2 and the comparative test positive electrode 1 were respectively used.

Each of the test secondary batteries 1 to 3 prepared above was charged to 4.2 V at a constant current of 0.1 C at 25 캜 and then charged at a constant voltage of 4.2 V until the charge current reached 0.1 mAh. Thereafter, the battery was allowed to stand for 60 minutes, and discharged at a constant current of 0.1 C until it reached 2.5 V, and the capacity of the first cycle was measured.

In this connection, Fig. 1 shows the charging and discharging capacities of the test secondary batteries 1 to 3 including the test electrodes 1 and 2 and the comparative test electrode 1, respectively. As shown in FIG. 1, in the case of the test secondary batteries 1 to 3, it was confirmed that the discharge capacity was not measured and only the charge capacity appeared. Thus, it can be confirmed that the irreversible anode additive used in Production Examples 1 to 3 exhibits irreversibility. In addition, it was confirmed that the irreversible anode additive prepared in Preparation Examples 1 and 2 had a much higher charge capacity than the cathode additive prepared in Comparative Preparation Example 1. This is because, in the case of the irreversible positive electrode additive prepared in Preparation Examples 1 and 2, the charging capacity of the irreversible positive electrode additive is improved by the reaction of the lithium oxide and the metal particles by including the lithium oxide as well as the metal particles. In addition, it can be confirmed that the charging capacity of the irreversible anode additive used in Production Example 1 is higher than that used in Production Example 2. This is because the smaller the average particle diameter of the metal particles contained in the irreversible positive electrode additive is, the more easily the reaction with the lithium oxide is performed to further improve the initial capacity.

Experimental Example  2: Characterization of secondary battery

The batteries prepared in Examples 1 to 7 and Comparative Example 1 were charged at a constant current of 0.1 C at a temperature of 25 ° C until the voltage reached 4.2 V and then charged at a constant voltage of 4.2 V until the charging current reached 0.1 mAh. Thereafter, the battery was allowed to stand for 60 minutes, discharged at a constant current of 0.1 C until it reached 2.5 V, and the capacity of the first cycle was measured. The energy density of the secondary batteries was measured by simulation.

The results are shown in Table 1 below.

	Energy density (Wh / L)
Example 1	805.2
Example 2	817.7
Example 3	830.4
Example 4	843.1
Example 5	847.1
Example 6	842.3
Example 7	836.6
Comparative Example 1	792.7

As shown in Table 1, Examples 1 to 7 including metal particles and lithium oxide as additives in the nickel-containing cathode active material had better energy densities than the secondary batteries of Comparative Example 1 in which additives were not used I could confirm.

This is because, in the case of Examples 1 to 7, the metal particles included as an irreversible additive in the nickel-containing positive electrode active material and the lithium oxide electrochemically react with each other during the initial charging (less than 2.5 V) , And an excessive amount of lithium is sent to the negative electrode at the time of initial charging to reduce the irreversible capacity of the negative electrode by lithiating the negative electrode.

In the case of Comparative Example 1, since no irreversible additive was included, lithium could not be additionally supplied to the cathode in addition to lithium released from the anode at the time of initial charging, and the initial capacity was also lower than those of Examples 1 to 7 according to the present invention.

Claims (19)

1. Nickel-containing cathode active material; And

   An anode comprising an additive comprising metal particles and lithium oxide.
2. The method according to claim 1,

   Wherein the additive comprises metal particles selected from the group consisting of Fe, Co, Cr, Mn, Ni, and combinations thereof.
3. The method according to claim 1,

   Wherein the additive comprises a lithium oxide selected from the group consisting of Li ₂ O, Li ₂ O ₂ , LiO ₂ , and combinations thereof.
4. The method according to claim 1,

   Wherein the metal particles and the lithium oxide are contained in a molar ratio of 1: 0.1 to 1: 4.
5. The method according to claim 1,

   Wherein the nickel-containing positive electrode active material is contained in an amount of 1 to 99 parts by weight based on the total weight of the positive electrode.
6. The method according to claim 1,

   Wherein the additive is included in an amount of 0.1 to 100 parts by weight based on the total weight of the positive electrode.
7. The method according to claim 1,

   Wherein the driving voltage of the nickel-containing positive electrode active material is 2.5 V to 4.3 V.
8. The method according to claim 1,

   Wherein the driving voltage of the additive is less than 2.5 volts.
9. The method according to claim 1,

   Wherein the average particle diameter of the metal particles is 5 占 퐉 or less.
10. The method according to claim 1,

    Wherein the anode further comprises a conductive material and a binder.
11. A lithium secondary battery comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode according to any one of claims 1 to 10.
12. 12. The method of claim 11,

    Wherein the negative electrode comprises a silicon-based negative active material.
13. 12. The method of claim 11,

    Wherein the additive comprising metal particles and lithium oxide reacts below the drive voltage range of the positive electrode active material to form lithium ions and metal oxides and the lithium ions migrate to the negative electrode.
14. 14. The method of claim 13,

    And the driving voltage of the positive electrode active material is 2.5 V to 4.3 V.
15. 14. The method of claim 13,

    And the driving voltage of the additive is less than 2.5 V.
16. Metal particles, and lithium oxide.
17. 17. The method of claim 16,

    Wherein the metal particles include one selected from the group consisting of Fe, Co, Cr, Mn, Ni, and combinations thereof.
18. 17. The method of claim 16,

    Wherein the lithium oxide comprises one selected from the group consisting of Li ₂ O, Li ₂ O ₂ , LiO ₂ , and combinations thereof.
19. 17. The method of claim 16,

    Wherein the metal particles and the lithium oxide are contained in a molar ratio of 1: 0.1 to 1: 4.

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