KR101611506B1 - Negative electrode active material for a lithium rechargable battery, methode for synthesising the same, and a lithium rechargable battery including the same - Google Patents

Abstract

The present invention relates to a negative electrode active material for a lithium secondary battery including GeO ₂ having a particle diameter of 1 nm to 50 nm, a method for producing the same, and a lithium secondary battery comprising the same.

Description

TECHNICAL FIELD The present invention relates to a negative electrode active material for a lithium secondary battery, a method for producing the negative electrode active material, and a lithium secondary battery including the lithium secondary battery, and a lithium secondary battery including the same. BACKGROUND ART [0002]

A negative electrode active material for lithium secondary batteries including GeO ₂ , a method for producing the same, and a lithium secondary battery comprising the same.

Lithium secondary batteries have attracted attention as power sources for driving electronic devices. Graphite is mainly used as a negative electrode material of a lithium secondary battery, but it is difficult to increase the capacity of a lithium secondary battery because the capacity per unit mass of graphite is as small as 372 mAh / g.

Examples of the anode material exhibiting a higher capacity than graphite include an alloy system such as silicon, tin and germanium, and an oxide system. These materials have the advantage of realizing high capacity and miniaturization of the battery.

However, these alloy or metal oxide based cathode materials have a large internal tension when combined with lithium. Thereby causing a loss of capacity due to pulverization during the charging / discharging process.

Efforts are being made to reduce the size of the negative electrode active material to nanometer size in order to reduce the tensile force generated when it bonds with lithium. However, at a few nanometers the quantum effect appears, and the electrochemical performance may deteriorate. Also, the surface energy increases with smaller particles, and the formation of secondary particles due to surface energy may lower the diffusion of lithium. So there is a range of particle sizes that gives the best performance per material. However, research on the particle size of the germanium-based oxide or alloy-based cathode material is still insufficient.

Disclosed is a negative active material for a lithium secondary battery comprising GeO ₂ having excellent electric conductivity and excellent charge / discharge characteristics and life characteristics, and a method for producing the same, and a lithium secondary battery comprising the same.

In one embodiment of the present invention, there is provided a negative active material for a lithium secondary battery comprising GeO ₂ having a particle size of 1 nm to 50 nm.

The particle size of the GeO ₂ may be specifically 4 nm to 30 nm.

The band gap of the GeO ₂ may be 5.3 eV to 5.8 eV.

The electrical conductivity of the GeO ₂ may be 1.0 x 10 ^-15 S / m to 1.0 x 10 ^-11 S / m.

The negative electrode active material may further include Ge having a particle diameter of 1 nm to 30 nm.

In another embodiment of the present invention, there is provided a method for producing GeCl ₄ , comprising: introducing GeCl ₄ into a solvent comprising 94 to 99% by volume of alcohol and 1 to 6% by volume of water; Mixing the GeCl ₄ and the solvent and reacting them; And removing the solvent to obtain GeO _{2. The} present invention also provides a method for producing a negative active material for a lithium secondary battery.

The GeCl ₄ may be added in an amount of 0.1 to 1 part per 100 parts of the solvent.

The alcohol may comprise methanol, ethanol, propanol, isopropanol, butanol, or a combination thereof.

The step of mixing and reacting the GeCl ₄ with a solvent may be performed at 0 ° C to 50 ° C.

The step of mixing and reacting the GeCl ₄ and the solvent may be performed for 5 to 20 hours.

The particle size of the obtained GeO ₂ may be 1 nm to 50 nm.

Another embodiment of the present invention provides a lithium secondary battery including the negative electrode, the positive electrode, and the electrolyte including the negative active material for the lithium secondary battery.

The negative electrode active material including GeO ₂ according to an embodiment and the lithium secondary battery including the same have excellent electric conductivity and excellent charge / discharge characteristics and life characteristics.

1 is an X-ray diffraction analysis graph for a negative electrode active material of an embodiment.
2 is a transmission electron micrograph of the negative active material of the embodiment
3 is an ultraviolet spectroscopic analysis graph of the negative electrode active material of the embodiment.
4 is a graph of an electrochemical impedance spectroscopy analysis of the battery of the Example.
5 is a graph showing the evaluation of the first charge / discharge characteristic of the battery of the embodiment.
6 is a transmission electron microscope photograph of the electrode plate after the first charge and discharge of the embodiment.
7 is a graph showing the life characteristics of the example at 0.2 C-rate.
FIG. 8 is a graph showing life characteristics of an embodiment at 1.0 C-rate.
Figure 9 is a voltage profile of an embodiment measured at 0.2 C-rate.
10 is a transmission electron micrograph of a negative electrode active material after charge and discharge in the embodiment.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

In one embodiment of the present invention, there is provided a negative active material for a lithium secondary battery comprising GeO ₂ having a particle size of 1 nm to 50 nm.

The particle size of the GeO ₂ may be specifically 1 nm to 35 nm, more specifically 4 nm to 30 nm, 4 nm to 20 nm, 4 nm to 15 nm and 4 nm to 11 nm.

The negative electrode active material including the GeO ₂ nanoparticles satisfying the above range of particle size has excellent electrochemical performance such as electrical conductivity and can improve the charge / discharge characteristics and life characteristics of the lithium secondary battery.

The band gap of GeO ₂ may be 5.3 eV to 5.8 eV, specifically 5.3 eV to 5.7 eV, 5.3 eV to 5.6 eV, and 5.3 eV to 5.5 eV. The band gap of GeO ₂ is a factor that can calculate the electric conductivity of GeO _{2. When} the band gap is within the above range, it can exhibit excellent electric conductivity.

The bandgap may be measured using an ultraviolet spectroscopy apparatus.

The electrical conductivity of the GeO ₂ is in the range of 1.0 x 10 ^-15 S / m to 1.0 x 10 ^-11 S / m, specifically 1.0 x 10 ^-14 S / m to 1.0 x 10 ^-11 S / m, 1.0 x 10 ^-13 S / m to 1.0 x 10 ^-11 S / m, and 1.0 x 10 ^-12 S / m to 1.0 x 10 ^-11 S / m. When the above range is satisfied, the charge transfer resistance is low and excellent battery characteristics can be realized.

The GeO ₂ nanoparticles can be divided into Ge particles and Li ₂ O particles during charging and discharging of the battery. The Ge particle size may be Ge of 1 nm to 30 nm.

In another embodiment of the present invention, there is provided a method for producing GeCl ₄ , comprising: introducing GeCl ₄ into a solvent comprising 94 to 99% by volume of alcohol and 1 to 6% by volume of water; Mixing the GeCl ₄ and the solvent and reacting them; And removing the solvent to obtain GeO _{2. The} present invention also provides a method for producing a negative active material for a lithium secondary battery.

Through the above process, GeO ₂ having a particle diameter of 1 nm to 50 nm can be produced, and the negative electrode active material for a lithium secondary battery including the same can exhibit excellent electrochemical characteristics and improve the charge / discharge characteristics and life characteristics of the battery.

The content of alcohol in the solvent is 94 to 99% by volume, specifically 95 to 99% by volume, 96 to 99% by volume, 94 to 98% by volume, 94 to 97% by volume, 95 to 98% .

The content of the water may be 1 to 6% by volume based on the total amount of the solvent, specifically 2 to 6% by volume, 3 to 6% by volume, 1 to 5% by volume, 1 to 4% by volume and 2 to 5% .

By using a solvent having a concentration in the above range, GeO ₂ nanoparticles having a particle diameter of 1 nm to 50 nm and a uniform particle size distribution can be produced.

The particle size of the GeO ₂ can be controlled by adjusting the concentration of the solvent, that is, by controlling the content of alcohol and water. Specifically, as the concentration of alcohol increases in the solvent concentration range, the resulting GeO ₂ particle size can be reduced.

In the solvent, the alcohol may include, for example, methanol, ethanol, propanol, isopropanol, butanol, or a combination thereof.

The particle size of the GeO ₂ obtained by changing the kind of the alcohol can be controlled. For example, when methanol is used, GeO ₂ having a particle size of 15 nm to 50 nm and 15 nm to 40 nm can be produced. As another example, when ethanol is used, GeO ₂ having a thickness of 5 nm to 25 nm and 5 nm to 20 nm can be produced, and 1 to 25 nm and 1 to 20 nm of GeO ₂ can be produced when isopropanol is used.

The GeCl ₄ may be added to the skin of the present invention in an amount of 0.1 to 1 part per 100 parts of the skin, and specifically 0.1 to 0.9 part skin, 0.1 to 0.8 part skin, 0.1 to 0.7 part skin, 0.1 to 0.6 part skin, 0.2 to 1 part 0.3 to 1 part skin, 0.2 to 0.9 part skin, 0.2 to 0.8 part skin can be injected. When the content of GeCl ₄ satisfies the above range, GeO ₂ nanoparticles having a particle size of 1 nm to 50 nm and a uniform particle size distribution can be produced.

The step of mixing and reacting the GeCl ₄ with a solvent may be carried out at 0 캜 to 50 캜 and may be carried out at 0 캜 to 40 캜, 0 캜 to 30 캜, 4 캜 to 50 캜, 4 캜 to 40 캜, 4 Lt; 0 > C to 30 < 0 > C. When the reaction temperature satisfies the above range, GeO ₂ nanoparticles having a particle diameter of 1 nm to 50 nm and a uniform particle size distribution can be produced.

The particle size of GeO ₂ obtained by controlling the reaction temperature can be controlled. Specifically, as the temperature is increased in the temperature range, the GeO ₂ particle size can be reduced. For example, proceed with the reaction at 4 ℃ particle size of 1nm to 25nm, 1nm to about 20nm in the case GeO can be produced _two, proceed with the reaction at room temperature, the particle size is prepared to 8nm to 50nm, 10nm to 40nm of GeO ₂ can do.

The step of mixing and reacting the GeCl ₄ with the solvent may be carried out for 5 to 20 hours, specifically 5 to 15 hours. The GeO ₂ nanoparticles having a particle size of 1 nm to 50 nm and a uniform particle size distribution can be prepared.

The particle size of GeO ₂ obtained by controlling the reaction time can be controlled. Specifically, by increasing the reaction time, GeO ₂ having a larger particle size can be obtained.

Another embodiment of the present invention provides a lithium secondary battery including the negative electrode, the positive electrode, and the electrolyte including the negative active material for the lithium secondary battery.

The negative electrode includes a current collector and a negative active material layer formed on the current collector, and the negative active material layer includes a negative active material.

The negative electrode active material layer includes a binder, and may optionally include a conductive material.

The binder serves to adhere the anode active material particles to each other and to adhere the anode active material to the current collector. As the binder, a water-insoluble binder, a water-soluble binder, or a combination thereof may be used.

Examples of the water-insoluble binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride , Polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

Examples of the water-soluble binder include styrene-butadiene rubber, acrylated styrene-butadiene rubber, polyvinyl alcohol, sodium polyacrylate, propylene and olefin copolymers having 2 to 8 carbon atoms, (meth) acrylic acid and (meth) Copolymers or combinations thereof.

The conductive material is used for imparting conductivity to the electrode. Any electrically conductive material can be used without causing any chemical change. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, Carbon-based materials; Metal powders such as copper, nickel, aluminum, and silver, or metal-based materials such as metal fibers; Conductive polymers such as polyphenylene derivatives; Or a mixture thereof may be used.

The collector may be selected from the group consisting of a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foil, a polymer substrate coated with a conductive metal, and a combination thereof.

The anode includes a current collector and a cathode active material layer formed on the current collector. As the cathode active material, a compound capable of reversibly intercalating and deintercalating lithium (a lithiated intercalation compound) can be used. Concretely, at least one of complex oxides of metal and lithium selected from cobalt, manganese, nickel, and combinations thereof may be used. As a more specific example, a compound represented by any one of the following formulas may be used.

Li _a A _{1 - b} X _b D ₂ (0.90? A? 1.8, 0? B? 0.5); Li _a A _{1 - b} X _b O _{2 - c} D _c (0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05); LiE _{1 - b} X _b O _{2 - c} D _c (0? B? 0.5, 0? C? 0.05); LiE _{2 - b} X _b O _{4 - c} D _c (0? B? 0.5, 0? C? 0.05); Li _a Ni _{1 -b- c} Co _b X _c D _? (0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <?? 2); Li _a Ni _{1 -b- c} Co _b X _c O _{2 -α} T _α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _{1 -b- c} Co _b X _c O _{2 - ?} T ₂ (0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? <2); Li _a Ni _{1 -b- c} Mn _b X _c D _? (0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <?? 2); Li _a Ni _{1 -b- c} Mn _b X _c O _{2- α} T _α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _{1 -bc} Mn _b X _c O _2-α T ₂ (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _b E _c G _d O ₂ (0.90? A? 1.8, 0? B? 0.9, 0? C? 0.5, 0.001? D? 0.1); Li _a Ni _b Co _c Mn _d G _e O ₂ (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li _a NiG _b O ₂ (0.90? A? 1.8, 0.001? B? 0.1); Li _a CoG _b O ₂ (0.90? A? 1.8, 0.001? B? 0.1); Li _a MnG _b O ₂ (0.90? A? 1.8, 0.001? B? 0.1); Li _a Mn ₂ G _b O ₄ (0.90? A? 1.8, 0.001? B? 0.1); Li _a MnG _b PO ₄ (0.90? A? 1.8, 0.001? B? 0.1); QO _2; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiZO ₂ ; LiNiVO _4; Li _(3-f) J ₂ (PO ₄ ) ₃ (0? F? 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0? F? 2); LiFePO ₄

In the above formula, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof; X is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements and combinations thereof; D is selected from the group consisting of O, F, S, P, and combinations thereof; E is selected from the group consisting of Co, Mn, and combinations thereof; T is selected from the group consisting of F, S, P, and combinations thereof; G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; Q is selected from the group consisting of Ti, Mo, Mn, and combinations thereof; Z is selected from the group consisting of Cr, V, Fe, Sc, Y, and combinations thereof; J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations thereof.

A compound having a coating layer on the surface of the compound may be used, or a compound having a coating layer may be mixed with the compound. The coating layer may comprise at least one coating element compound selected from the group consisting of oxides, hydroxides of coating elements, oxyhydroxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements. The compound constituting these coating layers may be amorphous or crystalline. The coating layer may contain Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof. The coating layer forming step may be any coating method as long as it can coat the above compound by a method which does not adversely affect the physical properties of the cathode active material (for example, spray coating, dipping, etc.) by using these elements, It will be understood by those skilled in the art that a detailed description will be omitted.

The cathode active material layer includes a binder and / or a conductive material.

The binder serves to adhere the positive electrode active material particles to each other and to adhere the positive electrode active material to the current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl Polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-acrylonitrile, styrene-butadiene rubber, Butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like, but not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any electrically conductive material can be used without causing any chemical change, and examples thereof include natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, , Metal powders such as nickel, aluminum, and silver, metal fibers, and the like, and conductive materials such as polyphenylene derivatives may be used alone or in combination.

As the current collector, aluminum may be used, but the present invention is not limited thereto.

The negative electrode and the positive electrode are prepared by mixing an active material, a conductive material and a binder in a solvent to prepare an active material composition and applying the composition to an electric current collector. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein. As the solvent, N-methylpyrrolidone or the like can be used, but it is not limited thereto.

In the non-aqueous liquid electrolyte secondary battery according to an embodiment of the present invention, the non-aqueous electrolyte includes a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

Depending on the type of the lithium secondary battery, a separator may exist between the positive electrode and the negative electrode. The separator may be a polyethylene / polypropylene double layer separator, a polyethylene / polypropylene / polyethylene triple layer separator, a polypropylene / polyethylene / poly It is needless to say that a mixed multilayer film such as a propylene three-layer separator and the like can be used.

Hereinafter, examples of the present invention will be described. The following examples are only illustrative of the present invention and are not intended to limit the scope of the present invention.

Example  One

(Preparation of negative electrode active material)

0.1 ml of GeCl ₄ (99.99%, Alfa Aesar) is added to a mixed solution of 26 ml of anhydrous isopropanol and 0.83 ml of ultrapure water. Stir the solution strongly at 4 ° C for 10 hours. To obtain a solid powder (GeO ₂₎ remaining after a sample dried at 5 mTorr at room temperature after the reaction.

(Manufacture of Battery)

After the polyvinylidene fluoride binder is dissolved in a solvent of N-methyl-2-pyrrolidone, the negative electrode active material and the carbon black conductive material prepared as described above are added to this solution to prepare a negative electrode active material slurry. The mixing ratio of the negative electrode active material, the conductive material and the binder is set to 8: 1: 1 by weight.

The slurry was coated on a copper foil and dried at 120 DEG C for 120 minutes to prepare an electrode plate.

A 2016R coin cell battery is manufactured using a lithium metal as a counter electrode plate and a mixed solution of 1.3M LiPF ₆ ethylene carbonate, ethyl methyl carbonate 3: 7 by volume and a 10% fluorethylene carbonate as an electrolyte.

Example  2 to 15

The anode active material was prepared in the same manner as in Example 1 except that the kind and content of alcohol and the reaction temperature were set as shown in Table 1 below, and batteries were prepared in the same manner as in Example 1.

Example Solvent (alcohol type) Alcohol Content (mL) Reaction temperature GeO ₂ Particle Size (nm) One Isopropanol 26 4 ℃ ~ 2 2 Isopropanol 23 4 ℃ 6 3 Isopropanol 20 4 ℃ 10 4 ethanol 26 4 ℃ 8 5 ethanol 23 4 ℃ 10 6 ethanol 20 4 ℃ 10 7 Isopropanol 26 Room temperature 11 8 Isopropanol 23 Room temperature 12 9 Isopropanol 20 Room temperature 15 10 ethanol 26 Room temperature 11 11 ethanol 23 Room temperature 13 12 ethanol 20 Room temperature 16 13 Methanol 26 Room temperature 18 14 Methanol 23 Room temperature 28 15 Methanol 20 Room temperature 35

Experimental Example  One: Geo ₂ Particle size evaluation

X-ray diffraction (XRD) is performed on the negative electrode active materials prepared in Examples 1 to 15 and the data are substituted into a Scherrer equation to measure the average size of the particles. The measured particle sizes are shown in Table 1 and Table 2 below.

1 is an X-ray diffraction analysis graph for negative electrode active materials of Examples 1 to 3 and Example 15. Fig.

The Scherrer equation can be expressed by the following equation (1).

[Equation 1]

In the above equation (1),? Is an average particle diameter, K is a shape factor,? Is an X-ray wavelength,? Is a half width (FWHM), and? Is a bragg angle.

FIG. 2 is a transmission electron microscope photograph of the negative electrode active materials of Examples 1 to 3 and Example 15. FIG. The particle size of the prepared negative electrode active material can also be measured by using a transmission electron microscope photograph as shown in FIG.

Table 2 is a table summarizing the changes in the particle size of GeO ₂ according to the kind and content of solvent and reaction temperature in Examples 1 to 15.

Reaction temperature Room temperature Reaction temperature 4 ℃ menstruum
content Methanol ethanol Isopropanol menstruum
content ethanol Isopropanol 20 mL 35 nm 16 nm 15 nm 20 mL 10 nm 10 nm 23 mL 28 nm 13 nm 12 nm 23 mL 10 nm 6 nm 26 mL 18 nm 11 nm 11 nm 26 mL 8 nm ~ 2 nm

Referring to Table 1, Table 2, and FIG. 2, it can be seen that GeO ₂ nanoparticles having various particle sizes of 1 nm to 50 nm in particle size were produced.

Also, referring to Table 2, it can be seen that the particle size of GeO ₂ obtained by controlling the type of solvent, the content (concentration) of solvent, and the reaction temperature can be controlled.

Experimental Example  2: Band gap  And electrical conductivity measurement

The bandgap is measured using the result of ultraviolet spectroscopic analysis of the negative electrode active material of the embodiment. Also, the electrical conductivity of the negative electrode active material is measured using the bandgap.

3 is an ultraviolet spectroscopic analysis graph of the negative electrode active materials of Examples 1 to 3, 13 and 15. The graph at the upper right of FIG. 3 is a graph showing the band gap according to the particle size.

Table 3 below shows the band gap and electric conductivity measurement results of the negative electrode active materials of Examples 1 to 3 and 15.

GeO ₂ size Example 1 Example 2 Example 3 Example 15 Band gap (eV) 5.77 5.45 5.42 5.38 Conductivity (S / m) 2.54 X 10 ^-15 1.52 X 10 ^-12 2.70 X 10 ^-12 6.2 X 10 ^-12

Referring to Table 3, it can be seen that as the particle size of GeO ₂ increases, the band gap becomes smaller and the electric conductivity becomes larger.

Experimental Example  3: Electrochemical stones  Impedance spectroscopy

Electrochemical impedance spectroscopy was performed on the cells prepared in Examples 2, 3 and 15 before charging and discharging, and the results are shown in FIG. In FIG. 4, the size of the semicircle represents the charge transfer resistance, which is consistent with the tendency of the conductivities of the respective embodiments.

Experimental Example  4: Charging and discharging  Character rating

The cells prepared in Examples 1 to 3 and 15 were charged and discharged at the first cycle at a rate of 0.05 C, and the results are shown in FIG.

All charge and discharge cycles are performed at 24 ° C and the voltage cutoff is set to 1.5V and 0.005V.

Referring to FIG. 5, it can be seen that the example shows excellent initial capacity.

Experimental Example  5: First Charging and discharging  Later On the plate  About TEM  Picture

The cells of the examples were firstly charged and discharged, and the electrode plates were observed by a transmission electron microscope (TEM). The results for Examples 1, 2 and 15 are shown in FIG.

GeO ₂ nanoparticles can be divided into Ge particles and Li ₂ O particles during charging and discharging. In FIG. 6, GeO ₂ and Ge particles can be identified.

Referring to FIG. 6, it can be seen that GeO ₂ nanoparticles of 2 nm, 6 nm, and 35 nm are changed to Ge particles and GeO ₂ particles of ~ 2 nm, ~ 5 nm, and ~ 10 nm after the first cycle.

Experimental Example  6: Evaluation of life characteristics

The life characteristics of the batteries of Examples 2 and 3 were evaluated at 0.2 C-rate, and the results are shown in FIG. In addition, the lifetime characteristics of the batteries of Examples 1 to 3 were evaluated at 1.0 C-rate, and the results are shown in FIG. 9 is a voltage profile measured at 0.2 C-rate for the cells of Examples 1 to 3. Fig.

Referring to FIGS. 7 to 9, the battery of Example shows excellent lifespan characteristics, and in particular, Example 2 having a particle size of 6 nm has excellent lifetime characteristics.

Experimental Example  7: Charging and discharging  For the negative electrode active material TEM  Picture

GeO ₂ particles aggregate in the Li ₂ O matrix during charging and discharging. The negative active material after charging and discharging of the cells of Examples 1, 2 and 15 was photographed with a transmission electron microscope and the results are shown in FIG.

Referring to FIG. 10, it can be seen that the smaller the particle size, the larger the aggregation phenomenon occurs. This is thought to be due to the high surface energy of the smaller particles.

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 present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (12)

And GeO ₂ having a particle diameter of 2 nm to 6 nm,
Wherein the band gap of the GeO ₂ is 5.45 eV to 5.77 eV. delete delete The method of claim 1,
And the electric conductivity of the GeO ₂ is 2.54 x 10 ^-15 S / m to 1.52 x 10 ^-12 S / m. The method of claim 1,
Wherein the negative electrode active material further comprises Ge having a particle diameter of 1 nm to 30 nm. GeCl ₄ into a solvent comprising 96 to 99% by volume of alcohol and 1 to 4% by volume of water;
Mixing the GeCl ₄ and the solvent and reacting at 0 ° C to 50 ° C for 5 to 20 hours; And
And removing the solvent to obtain GeO ₂ having a particle diameter of 2 nm to 6 nm. The method of claim 6,
Wherein the GeCl ₄ is added in an amount of 0.1 to 1 part per 100 parts of the skin of the solvent. The method of claim 6,
Wherein the alcohol includes methanol, ethanol, propanol, isopropanol, butanol, or a combination thereof. delete delete delete A negative electrode comprising the negative electrode active material for a lithium secondary battery according to any one of claims 1, 4, and 5,
Anode, and
A lithium secondary battery comprising an electrolyte.

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