KR20100056251A - Negative active material for lithium secondary battery, method of preparing thereof, and lithium secondary battery including same - Google Patents

Abstract

PURPOSE: A negative active material used for a secondary lithium battery is provided to obtain structural stability by preventing phase analysis even when charging/discharging is repetitively practiced at 0-1.5V and to have superior cycle lifetime and capabilities. CONSTITUTION: A negative active material used for a secondary lithium battery includes an Mo_xM_yP_z compound. In the compound, M is selected from a group comprising Co, Mn, Fe, Ni, Zn, and combinations thereof. The negative active material has a nanoparticle cluster shape. A method for manufacturing the negative active material comprises a step of mixing Mo, metal M, and P and a step of plasticizing mixture powder after milling the mixture. The lithium secondary battery includes an anode(3) including anodic active material, a cathode(2) including the negative active material, and an electrolyte.

Description

A negative active material for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery including the same TECHNICAL FIELD The present invention relates to a negative electrode active material for a lithium secondary battery, and a lithium secondary battery including the same.

The present invention relates to a negative electrode active material for a lithium secondary battery and a lithium secondary battery including the same, and more particularly, to a negative electrode active material for a lithium secondary battery excellent in capacity retention and a lithium secondary battery including the same.

Recently, with the trend toward miniaturization and light weight of portable electronic devices, the need for high performance and high capacity of batteries used as power sources for these devices is increasing.

A battery generates power by using a material capable of electrochemical reactions at a positive electrode and a negative electrode. A typical example of such a battery is a lithium secondary battery that generates electric energy by a change in chemical potential when lithium ions are intercalated / deintercalated at a positive electrode and a negative electrode.

The lithium secondary battery is prepared by using a material capable of reversible intercalation / deintercalation of lithium ions as an active material of a positive electrode and a negative electrode, and filling an organic electrolyte or a polymer electrolyte between the positive electrode and the negative electrode.

As a cathode active material of a lithium secondary battery, a lithium composite metal compound is used. Examples thereof include a composite of LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _1-x Co _x O ₂ (0 <x <1), LiMnO _2, and the like. Metal oxides are being studied.

As the negative electrode active material, various types of carbon-based materials including artificial graphite, natural graphite, and hard carbon capable of inserting / desorbing lithium have been applied. The graphite of the carbon series has a low discharge voltage of -0.2V compared to lithium, and the battery using this negative electrode active material exhibits a high discharge voltage of 3.6V, which provides an advantage in terms of energy density of the lithium battery and also has excellent reversibility in lithium secondary. It is most widely used to ensure the long life of the battery. However, the graphite active material has a problem of low capacity in terms of energy density per unit volume of the electrode plate due to the low graphite density (theoretical density of 2.2 g / cc) in the production of the electrode plate, and side reaction with the organic electrolyte used at high discharge voltage is likely to occur. Risk of fire or explosion due to battery malfunction or overcharging.

In order to solve this problem, research on a non-carbon negative electrode active material has recently been conducted. Examples thereof include metal phosphides such as MnP ₄ . The MnP ₄ showed a primary transition of redox transition from MnP ₄ to Li ₇ MnP ₄ at 0.57 V and higher, and the initial discharge capacity and the charge capacity were excellent at 1150 mAh / g and 700 mAh / g, respectively. Afterwards, the capacity was reduced to 350mAh / g.

In addition, the MnP ₄ phase is a cubic phase Li ₇ MnP ₄ is obtained at 0.5V or more, which is decomposed into Mn and Li ₃ P below 0.5V, there is a problem that reversibility is significantly lowered.

In contrast to binary MP _n systems, the ternary Li ₂ CuP ₂ and Li ₇ MP ₄ , where M is Ti or V, together with structural rearrangements in the lithium reaction, Represents the order phase transition.

In addition, ternary tetragonal Li _5.5 Mn _2.5 P ₄ does not decompose at 0V and exhibits a reversible capacity of 700mAh / g after 30 charge / discharge cycles. This is impossible and practically unlikely because of the risk of explosion.

Recently, orthorhombic SnP _0.94 nanoparticles obtained by pyrolysis of organic precursors show reversible insertion and desorption of lithium ions between 1.2 and 0V at a rate of 120 mAh / g, with initial charge and discharge capacity of 850 mAh, respectively. / g and 740 mAh / g, showing a high coulombic efficiency of about 87%. In addition, the capacity retention rate after the 40 times charging and discharging compared to the initial charging capacity was about 92%.

That is, the tetragonal SnP _0.94 has a relatively good level of capacity characteristics and cycle characteristics compared to other binary or ternary phosphides, but this also shows a satisfactory level of capacity characteristics and cycle life characteristics. no.

The present invention is to provide a negative electrode active material for a lithium secondary battery excellent in capacity retention.

The present invention also provides a method for producing the negative electrode active material.

The present invention also provides a lithium secondary battery including the negative electrode active material.

Technical problems to be achieved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

According to an embodiment of the present invention, Mo _x M _y P _z (The M is selected from the group consisting of Co, Mn, Fe, Ni, Zn and combinations thereof, 0.9≤x≤1, 0≤y≤ 0.1 and 1.9 ≦ z ≦ 2.1) to provide a negative electrode active material including the compound.

According to another embodiment of the invention, the steps of mixing Mo, metal M, and P; And it provides a method for producing a negative electrode active material for a lithium secondary battery comprising the step of firing the mixture after milling.

According to another embodiment of the present invention, a lithium secondary battery including the negative electrode active material is provided.

The negative electrode active material of the present invention is excellent in capacity retention.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, by which the present invention is not limited and the present invention is defined only by the scope of the claims to be described later.

The negative electrode active material according to the embodiment of the present invention includes a Mo _x M _y P _z compound.

The M is preferably selected from the group consisting of Co, Mn, Fe, Ni, Zn, and combinations thereof, and more preferably M is Zn. M increases the electrical conductivity to reduce polarization during charge and discharge.

In addition, it is preferable that x is in the range of 0.9 ≦ x ≦ 1, y is in the range of 0 ≦ y ≦ 0.1, and Z is in the range of 1.9 ≦ z ≦ 2.1, and more preferably x is 0.97 ≦. It is preferable that x is in the range of x ≦ 1, y is in the range of 0 ≦ y ≦ 0.05, and z is in the range of 1.98 ≦ z ≦ 2. Structural stabilization can be achieved when x, y, and z are in this range.

In addition, the Mo _x M _y P _z anode active material It may be crystalline, amorphous, or a mixture thereof, and crystalline is more preferred because the structure is stabilized.

In addition, the negative electrode active material is preferably in the form of nanoparticle clusters in which nanoparticles are collected.

It is preferable that the nanoparticles of the nanoparticle cluster have an average particle size of 5 to 30 nm, and more preferably have an average particle size of 5 to 10 nm. In the above range, the diffusion distance of Li ions is reduced, so that the removal and insertion can proceed quickly.

Moreover, it is preferable that the said nanoparticle cluster has an average particle diameter of 5-20 micrometers, and it is more preferable to have an average particle diameter of 10-20 micrometers. In the above range, there is an advantage that the electrode plate density is improved .

The Mo _x M _y P _z (M is selected from the group consisting of Co, Mn, Fe, Ni, Zn, and combinations thereof, 0.9≤x≤1, 0≤y≤0.1, 1.9≤z≤2.1 Compound is very reversible to lithium ions, the lithium ions are inserted into Mo _x M _y P _z during charging and discharging, Li _t Mo _x M _y P _z (0.9≤x≤1, 0≤y≤0.1, 1.9 ≤ _z ≤ 2.1, 0 ≤ t ≤ 5) is formed and detached again so that the reaction to Mo _x M _y P _z is reversibly smooth, and thus the cycle life characteristics are very excellent. In particular, even when charging and discharging is repeatedly performed at less than 2V, preferably 0 to 1.5V, phase decomposition does not occur with an alloy such as Li ₃ P and the like and is structurally stable. In addition, the capacity characteristics are also very good.

In addition, Mo _x M _y P _z of the present invention (M is selected from the group consisting of Co, Mn, Fe, Ni, Zn, and combinations thereof, 0.9≤x≤1, 0≤y≤0.1, 1.9≤ z≤2.1) negative electrode active material is a carbon-based material, a lithium metal, an alloy of lithium metal, a material that can be applied and undoped on lithium, or a material capable of reacting with lithium ions to form a lithium-containing compound reversibly, or transition metal It can be used by mixing with an oxide etc.

As the carbon-based material, any carbon-based negative electrode active material generally used in a lithium secondary battery may be used, and typically, crystalline carbon such as natural graphite or artificial graphite, soft carbon, and hard carbon. amorphous carbon such as carbon), and specific examples thereof include carbon black, acetylene black, activated carbon, carbon fiber, fullerene, single wall carbon nanotube (SWNT), multiwall carbon nanotube (MWNT), carbon Nanowires, carbon nano-horns (carbon nano-horn), or carbon nano rings (carbon nano ring) and the like, but are not limited thereto.

As the alloy of the lithium metal, lithium and Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, Sn, or these Alloys of metals selected from the combination can be used.

Examples of dope and undoped materials for lithium, materials capable of reversibly reacting with lithium to form compounds, or transition metal oxides include vanadium oxide, lithium vanadium oxide, Si, SiO _x (0 <x <2), Si-Y alloy (Y is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, transition metals, rare earth elements and combinations thereof, not Si), Sn, SnO ₂ , Sn-Y (Y is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, transition metals, rare earth elements, and combinations thereof, and not Sn); At least one of these and SiO ₂ may be mixed and used. As the element Y, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

The negative electrode active material having the above characteristics may include mixing Mo, metal M, and P; And it may be prepared by a manufacturing method comprising the step of milling and then firing the mixture.

More specifically, first, Mo, metal M, and P are mixed (S1).

In this case, M is selected from the group consisting of Co, Mn, Fe, Ni, Zn, and combinations thereof.

The Mo, the metal M, and P may be used by mixing as appropriate so that the molar ratio of x, y, and z defined in the formula (1).

Subsequently, the mixture is milled and then fired (S2).

It is preferable to advance at the speed of 800 rpm or less, and, as for the said milling process, it is more preferable to advance at the speed of 400-800 rpm. When the speed range is exceeded, impurities such as Fe may occur in the ball used in the milling process, which is not preferable.

The milling process It is preferable to carry out under inert gas, such as argon, helium, neon, xylene (Xe), or a mixture of these, and it is more preferable to carry out under argon gas. This is to prevent the reaction of moisture-sensitive metals or alloys of metals with moisture.

The firing process may be carried out at an appropriate temperature (for example, room temperature) for a suitable time, and there is no need to specifically limit the firing temperature and firing time.

The present invention also provides a lithium secondary battery comprising a negative electrode active material prepared by the manufacturing method.

A lithium secondary battery according to another embodiment of the present invention includes a negative electrode including a negative electrode active material, a positive electrode including a positive electrode active material, and an electrolyte present therebetween.

In this case, the negative electrode active material is the same as described above.

1 is an exploded perspective view of a rechargeable lithium battery according to one embodiment of the present invention. Referring to FIG. 1, the lithium secondary battery 1 includes a negative electrode 2 and a positive electrode 3, a separator 4 disposed between the negative electrode 2 and the positive electrode 3, and the negative electrode ( 2), the electrolyte (not shown) impregnated in the positive electrode 3 and the separator 4, the battery container 5, and the sealing member 6 which encloses the said battery container 5 are comprised as a main part. . The negative electrode 2 and the positive electrode 3 may be prepared by forming a mixture in the form of a film on a current collector for a negative electrode or a positive electrode active material forming composition including respective negative electrode active materials or positive electrode active materials. In this case, the mixture is prepared by directly coating the positive electrode or negative electrode active material composition on a current collector and then drying or casting the active material composition on a separate support, and then laminating the film obtained by peeling from the support onto the current collector. Can be prepared.

In addition, the composition for forming the negative electrode or the positive electrode active material may be prepared by dissolving or dispersing the negative electrode or the positive electrode active material, the binder, and the conductive agent in a solvent.

In this case, the negative electrode active material is the same as described above.

In the present invention, the positive electrode active material is not particularly limited, and a compound capable of intercalation / deintercalation of lithium ions is possible. Typically, as the cathode active material, a metal oxide, a lithium composite metal oxide, a lithium composite metal sulfide, a lithium composite metal nitride, or the like is used.

The binder is a chemical substance that is stable in an electrochemical reaction, and functions as a paste for the active material, mutual adhesion between the active materials, adhesion between the active material and the current collector, and a buffering effect on the expansion and contraction of the active material. Such a binder may be selected from the group consisting of water-soluble organic polymers, water-insoluble organic polymers and mixtures thereof. As the water-soluble organic polymer, polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, isopropyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, cyanoethyl cellulose, ethyl-hydroxyethyl It is preferably selected from the group consisting of cellulose, polyoxyethylene, poly N-vinylpyrrolidone, polyvinylacetate and mixtures thereof. In addition, the water-insoluble organic polymer may be polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene polymer, trifluoroethylene polymer, difluoroethylene polymer, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene Hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkylvinylether copolymer, trifluoroethylene chloride polymer, polyethylene, polypropylene, and mixtures thereof.

The conductive agent is used to impart conductivity to the electrode, and any battery can be used as long as it is an electron conductive material without causing chemical change in the battery. Carbon materials, such as amorphous carbon, such as acetylene black and Ketjen black, and graphite structure carbon, or metal materials, such as nickel, copper, silver, titanium, platinum, aluminum, cobalt, iron, chromium, can be used. Such a conductive agent may be spherical, flake, filamentary, fibrous, spiked, or needle-like, and it is preferable to use a mixture of the two shapes to increase the tap density.

In addition, the solvent uses N-methylpyrrolidone (NMP), acetone, tetrahydrofuran, decane, and the like, and preferably N-methylpyrrolidone.

At this time, the composition of the positive electrode active material, the negative electrode active material, the conductive agent, the binder, the solvent for producing the electrode is appropriately selected within a known range, the production method is preferably selected by those skilled in the art.

The current collector collects electrons generated by the electrochemical reaction of the active material or serves to supply electrons required for the electrochemical reaction. The material of the current collector may be stainless steel, aluminum, nickel, copper, titanium, carbon, conductive resin, or the like in which carbon, nickel, or titanium is treated on the surface of copper or stainless steel. A current collector made of material and a current collector made of copper can be used as the negative electrode.

The electrolyte serves as a medium for transporting lithium ions in the positive electrode and the negative electrode, and a non-aqueous electrolyte or a known solid electrolyte may be used. For example, as the non-aqueous electrolyte, a lithium salt dissolved in a non-aqueous organic solvent may be used.

The lithium salt is LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCl, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li (CF ₃ SO ₂ ) ₂ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiB ₁₀ Cl ₁₀ , LiCl, LiBr, LiI, and mixtures thereof.

The non-aqueous organic solvent is not particularly limited to serve as a medium through which ions involved in the electrochemical reaction of the battery may move, but may include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate; Chain carbonates such as dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate; Esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and γ-butyrolactone; Ethers such as 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane and 2-methyltetrahydrofuran; Nitriles such as acetonitrile; Amides, such as dimethylformamide, etc. can be used. These can be used individually or in mixture of multiple pieces. In particular, a mixed solvent of a cyclic carbonate and a linear carbonate can be preferably used.

The solid electrolyte is Li ₄ SiO ₄ , Li ₄ SiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₃ PO ₄ -Li ₂ S-SiS ₂ , phosphorus sulfide compound, polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethylmethacrylate (PMMA), polyvinylidene fluoride (PVDF), and mixtures thereof.

The lithium secondary battery 1 including these includes a separator 4 capable of blocking electron conduction between the cathode 2 and the anode 3 and conducting lithium ions. The separator 4 plays an important role in improving stability as well as separating the positive electrode and the negative electrode. As the separator, any one commonly used in a lithium secondary battery may be used. For example, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more thereof may be used.

The shape of the lithium secondary battery according to the present invention having such a component may be any shape such as coin type, button type, sheet type, stacked type, cylindrical type, flat type, rectangular type, and those skilled in the art by those skilled in the art. Design and apply accordingly.

The lithium secondary battery of the present invention can be widely used in portable information terminals, portable electronic devices, small household power storage devices, motorcycles, electric vehicles, hybrid electric vehicles, and the like.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following examples are only preferred examples of the present invention and the present invention is not limited to the following examples.

Example 1 Preparation of Anode Active Material

The stoichiometric amount (30 g) of Mo (99.9% of Aldrich) and P (99.9% of Aldrich) was placed in a 200 ml stainless steel container. At this time, the molar ratio of Mo and P was 1: 2. Subsequently, the steel balls were put together in a steel container such that the MoP ₂ and the steel balls had a weight ratio of 1:30 .

It was then sealed in a glove box filled with pure argon gas and rotated for 10 hours at a speed of 800 rpm using a high speed milling machine to prepare an active material of MoP ₂ . The molar ratio of P to Mo of the MoP ₂ active material was 2.01 as a result of inductively coupled plasma-mass spectroscopy (ICP-MS) analysis.

Example 2: Fabrication of Lithium Secondary Battery

80 wt% of the MoP ₂ active material prepared in Example 1, 10 wt% of the polyvinylidene fluoride binder, and 10 wt% of the super P carbon black conductive agent were mixed, and then coated on a copper current collector to prepare a negative electrode.

The negative electrode, microporous polyethylene separator, and 1.05 M LiPF ₆ were dissolved in ethylene carbonate / diethylene carbonate / ethylmethyl carbonate (EC / DEC / EMC = 30: 30: 40% by volume). Using an electrolyte solution, a coin-type half cell of 2016 type was manufactured.

Comparative Example 1

Using a commercially available MoP ₂ having a particle size of 20 μm or more as a negative electrode active material, a 2016 type coin-type half cell was manufactured in the same manner as in Example 2.

* TEM photo

A TEM image of the negative electrode active material prepared in Example 1 is shown in FIG. 2A, and a magnification thereof 100,000 times is shown in FIG. 2B.

Referring to Figure 2a, it can be seen that the negative electrode active material prepared in Example 1 is a nanoparticle cluster shape of the average particle diameter of about 5㎛ composed of nanoparticles having an average particle size of 10nm or less. In addition, the formation of the MoP ₂ crystal phase was confirmed from the selected area diffraction pattern (SADP) inserted in Figure 2b.

* X-ray diffraction measurement

3 shows the XRD pattern of the negative electrode active material after charging and discharging the coin-type half battery manufactured in Example 2 at a rate of 0.1 C at a voltage of 0 to 1.5 V for 60 times.

Referring to Figure 3, after 60 charge and discharge it can be seen that only the peak of the MoP ₂ phase.

 From this, it was confirmed that phase decomposition did not occur when charging and discharging at a cut-off voltage of 1.5V.

Cycle life characteristics

The coin-type half-cells manufactured in Example 2 and Comparative Example 1 were charged and discharged at a rate of 0.2 C (= 160 mAh / g) at 0 to 1.5 V to measure the relationship between the voltage profile, charge capacity and cycle life. The results for Example 2 are shown in FIGS. 4A and 4B.

Figure 4a shows the voltage profile of the coin-type half-cell prepared in Example 2 when charged, discharged once, 10 times, 20 times, 30 times, and 60 times at a rate of 0.2C at 0 to 1.5V, 4B shows the relationship between the charge capacity and the cycle life when the coin-type half battery manufactured in Example 2 was charged and discharged at a rate of 0.2C at a voltage of 0 to 1.5V.

Referring to FIGS. 4A and 4B, when the cutoff voltage is 1.5 V, the one-discharge capacity and the charging capacity were 817 mAh / g and 719 mAh / g, the coulomb efficiency was about 88%, and the reversible capacity after 60 charge / discharge was 669 mAh /. g, and the dose retention was very high at about 93%. This is because, unlike other metal phosphides, MoP ₂ of Example 1 does not decompose into Li _n P even after 60 charge / discharge cycles, even at 0V.

However, the discharge capacity of the coin-type half-cell manufactured in Comparative Example 1 was 164 mAh / g and the capacity retention rate was 20%, and the discharge capacity was 100 mAh / g at 60 charge / discharge cycles and the capacity retention was about 12.16.

Therefore, it was confirmed that the capacity retention rate was significantly lower than that in Example 2.

That is, when compared with Comparative Example 1, showing the other two sources of metal phosphide are fast capacity reduction, such as, MoP ₂ is to check to show an improved life stability, in this from the improved life stability and the capacity retaining ratio, MoP ₂ It can be seen that the Li reaction is different from other metal phosphides.

All simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

1 is an exploded perspective view of a rechargeable lithium battery according to one embodiment of the present invention.

Figure 2a is a TEM photograph of the negative electrode active material prepared in Example 1.

FIG. 2B is an enlarged view of 100,000 times of FIG. 2A.

FIG. 3 is a graph showing an XRD pattern of a negative electrode active material after charging and discharging a coin-type half battery prepared in Example 2 at a voltage of 0 to 1.5V 60 times.

4A is a graph showing a voltage profile when the coin-type half battery prepared in Example 2 is charged and discharged at 0 to 1.5V.

4C is a graph showing the relationship between the charge capacity and the cycle life when the coin-type half battery manufactured in Example 2 was charged and discharged at a voltage of 0 to 1.5V.

Claims (11)

Mo _x M _y P _z (The M is selected from the group consisting of Co, Mn, Fe, Ni, Zn, and combinations thereof, 0.9≤x≤1, 0≤y≤0.1, 1.9≤z≤2.1 A negative electrode active material for a lithium secondary battery containing a compound. The method of claim 1, The negative active material is The negative electrode active material for lithium secondary batteries which is a nanoparticle cluster shape. The method of claim 1, Wherein M is Zn negative electrode active material for a lithium secondary battery. The method of claim 2, The nanoparticle cluster is a negative active material for a lithium secondary battery containing nanoparticles having an average particle size of 5 to 30nm. The method of claim 2, The nanoparticle cluster is a negative active material for a lithium secondary battery having an average particle diameter of 5 to 20㎛. Mixing Mo, metal M, and P; And Milling the mixture and then firing Method for producing a negative electrode active material for a lithium secondary battery comprising a. A positive electrode including a positive electrode active material; A negative electrode including a negative electrode active material; And Contains an electrolyte, The negative electrode active material is Mo _x M _y P _z (The M is selected from the group consisting of Co, Mn, Fe, Ni, Zn, and combinations thereof, 0.9≤x≤1, 0≤y≤0.1, 1.9≤ z≤2.1) lithium compound comprising a compound. The method of claim 7, wherein The negative active material is A lithium secondary battery having a nanoparticle cluster shape. The method of claim 7, wherein M is Zn is a lithium secondary battery. The method of claim 8, The nanoparticle cluster is a lithium secondary battery comprising nanoparticles having an average particle size of 5 to 30nm. The method of claim 8, The nanoparticle cluster is a lithium secondary battery having an average particle diameter of 5 to 20㎛.

Images