KR19980078121A - Lithium Mn2O4 powder cathode active material for lithium secondary battery - Google Patents

Abstract

The present invention relates to the preparation of Li _x Mn ₂ O ₄ powder, which is a cathode active material for lithium secondary batteries, and its electrochemical properties to Li / polymer electrolyte (PAN / Li _1.03 Mn ₂ O ₄ battery and Li / 1M LiBF4-EC / DEC solution / Li _1.03). is investigated by using a Mn ₂ O ₄ cells. in the present invention, less mixing (cation mixing) the cation to chelating agent (chelating agent) as for producing Li _x Mn ₂ O ₄ powder of pure phase (phase-pure) Li _x Mn ₂ O ₄ powder was prepared by using a sol-gel method using glycolic acid as a precursor and lithium (Li) and manganese (Mn) acetate as precursors. The physicochemical characteristics were XRD, BET, Rietvelt program and SEM. The charge and discharge characteristics of the battery were Li / Polymer / Li _1.03 Mn ₂ O ₄ battery and Li / 1M LiBF. ₄ -EC / DEC solution / Li _1.03 was investigated using a Mn ₂ O ₄ cells. Li _X Mn ₂ O ₄ exertion of the present invention when changing the firing temperature, and goat glycol The microstructure was adjusted.

Description

Anode Active LixMn2O4 Powder for Lithium Secondary Battery

1 is a manufacturing process chart of Li _1.03 Mn ₂ O ₄ powder by the sol-gel method showing the manufacturing process according to the present invention.

2 is a diagram showing the TG grains (raising rate of 5 ℃ / min) showing the process of conversion from the gel (gel) precursor to the cerammix according to the present invention.

3 is a graph showing an XRD pattern graph of Li _1.03 Mn ₂ O ₄ powder according to the firing temperature of the gel precursor when the glycolic acid mole ratio to total metal ions of the present invention is 1.5.

4 is a chart showing the lattice phase [a] dependence of Li _1.03 Mn ₂ O ₄ powder according to the firing temperature of the gel precursor when the glycolic acid molar ratio to total metal ions according to the present invention is 1.5.

5 is a diagram showing the specific surface area dependence of Li _1.03 Mn ₂ O ₄ powder according to the firing temperature of the gel precursor when the glycolic acid molar ratio to total metal ions according to the present invention is 1.5.

6 shows Li _1.03 Mn ₂ O ₄ powder calcined at 800 ° C. when the glycolic acid molar ratio to total metal ions according to the present invention is (a) 0.5, (b) 1.0, (c) 1.5 and (d) 2.0. Is a graph showing the XRD pattern graph

7 is a graph showing the lattice constant [a] dependence on the molar ratio of glycolic acid to total metal ions of Li _1.03 Mn ₂ O ₄ powder calcined at 800 ° C. according to the present invention.

8 is a graph showing the specific surface area dependence of the molar ratio of glycolic acid to total metal ions of Li _1.03 Mn ₂ O ₄ powder calcined at 800 ℃ according to the present invention.

9 is a powder sample prepared at a firing temperature of (a) 300 ° C. (b) 650 ° C., (c) 750 ° C. and (d) 800 ° C. when the glycolic acid molar ratio to metal ion according to the present invention is 1.5. SEM photograph showing the surface of the.

FIG. 10 is an SEM photograph showing the surface of a powder sample prepared at a firing temperature of 700 ° C. of a gel precursor when the glycolic acid molar ratio to total metal ions (a) 2.0 and (b) 0.5 according to the present invention.

FIG. 11 shows Li / 1M LiBF ₄ -EC / DEC solution using Li _1.03 Mn ₂ O ₄ powder calcined at 760 ° C. when the glycolic acid molar ratio to (a) 1.5 and (b) 0.75 according to the present invention. / Li _1.03 Mn ₂ O _{4 This} is a graph showing the discharge capacity graph according to the cycle for the current density of 1 mA / cm ² voltage range 3.4 ~ 4.3V of the battery.

12 is a constant current density of 0.1 mA in the voltage range of 3.4 ~ 4.3V of Li / polymer electrolyte (PAN) / Li _1.03 Mn ₂ O ₄ battery using Li _1.03 Mn ₂ O ₄ powder calcined at 760 ℃ according to the present invention / cm ² (a) Charge / discharge graph according to cycle (b) The graph showing the discharge capacity graph different from the cycle.

FIG. 13 is a chart showing charge and discharge curves of Li / polymer electrolyte (PAN) / Li _1.03 Mn ₂ O ₄ cells at various charge and discharge current densities according to the present invention.

14 is a chart showing the discharge capacity curve according to the number of cycles of Li / polymer electrolyte (PAN) / Li _1.03 Mn ₂ O ₄ cells at various charge and discharge current density according to the present invention.

[Field of Invention]

The present invention relates to a method for producing a cathode active material powder for a lithium secondary battery.

More specifically, the present invention relates to a method for producing Li _1.03 Mn ₂ O ₄ powder, which is a positive electrode active material for a lithium ion battery and a lithium polymo battery, which are lithium secondary batteries.

More specifically, the present invention provides a method for preparing Li _1.03 Mn ₂ O ₄ and a Li / Polymer electrolyte (PAN) / Li _1.03 Mn ₂ O ₄ battery and a Li / 1M LiBF ₄ -EC / DEC solution / Li _1.03 Mn ₂ O ₄ battery. The electrochemical properties were studied using.

[Background of invention]

The most common method for producing LiMn ₂ O ₄ , a cathode active material, is a solid phase reaction method. In this method, the carbonate and hydroxide of each element is used as a raw material, and these powders are mixed and fired several times.

In the ceramic manufacturing field, a sol-gel method is being developed, which dissolves a metal alkoxide in a solvent, and then forms a sol state through hydrolysis and polymerization reaction, and the temperature and concentration of the dispersion and Other conditions are changed to gel to obtain ceramic powder through drying and heat treatment.

Disadvantages of the solid phase reaction method include high impurity inflow from the ball mill during mixing, inhomogeneous reaction, which is difficult to obtain a uniform phase, and it is difficult to control the size of the powder particles uniformly. Long manufacturing time The sol-gel method using metal alkoxide is not economical because the metal alkoxide price is too expensive. Therefore, in recent years, citric acid and Pechini methods using metal nitrate, acetate and sulfate as metal precursors and citric acid and ethylene glycol as chelating agents are widely used. Is being studied. Since the physical properties of the prepared powders depend on the type of chelating agent (chelatinf agent), it is necessary to select an appropriate chelating agent.

[Purpose of invention]

An object of the present invention is to use a glycol acid (glycolic acid) as a chelating agent (chelating agent), as a metal precursor using a sol-gel (sol-gel) method using lithium acetate and manganese acetate Li _x Mn ₂ O ₄ to prepare a powder.

Another object of the present invention is to prepare a phase-pure Li _x Mn ₂ O ₄ powder with low cation mixing using glycolic acid as a chelating agent.

Another object of the present invention is to prepare a sol-gel method using glycolic acid as a chelating agent to investigate the physical and chemical properties and the charge and discharge characteristics of the battery.

[Summary of invention]

Li _x Mn ₂ O ₄ of the positive electrode active material for a lithium secondary battery of the present invention is made of a gel precursor using lithium (Li) acetate and manganese (Mn) acetate as a metal precursor and glycolic acid as a chelating agent. This gel precursor is Li _x Mn ₂ O ₄ powder prepared by heat treatment at 200-900 ° C. for 5-30 hours under inert gas or oxidizing atmosphere.

Instead of the lithium acetate and manganese acetate, lithium nitrate or lithium hydroxide and manganese nitrate or gamma-manganese peroxide hydroxide ( -MnOOH) can be used as a metal precursor. The ratio of lithium (Li) and manganese (Mn) in the lithium acetate (or lithium nitrate) and manganese acetate (or manganese nitrate) used is preferably 1 to 1.1: 1.

The Li _X Mn ₂ O ₄ powder of the present invention is used as a cathode active material of a lithium ion battery or a lithium polymer battery which is a lithium secondary battery. A thin film may be prepared by solting a solution of Li _X Mn ₂ O ₄ of the present invention. .

The positive electrode active material Li _X Mn ₂ O ₄ powder has a uniform particle size and can adjust the microstructure, such as the particle size, specific surface area, cubic structure lattice constant.

Detailed Description of the Invention

Lithium secondary batteries are attracting much attention as future portable power sources because they have various characteristics such as energy density, high operating voltage, and no memory effect, compared to conventional secondary batteries. The research of lithium secondary batteries began to be actively conducted in the 1970s. In the early stages, batteries using a negative electrode as a lithium foil and a metal chalcogenide as a positive electrode were developed. The internal short with dentrite growth has been found to be a safety problem. Since then, so-called lithium-ion batteries have emerged with Sony as the cathode material and carbon oxides as the cathode materials, such as Li _x CoO ₂ , Ll _x NiO ₂ , and Li _x Mn ₂ O ₄ . Among them, the cathode has a relatively low capacity of 148 to 274 mAh / g and a real capacity of 110 to 200 mAh / g, while the cathode has a theoretical capacity of 372 mAh / g (based on Li ₁ C ₆ ). There is an urgent need to develop new cathode materials and to improve the properties of existing anode materials to make more use of theoretical capacity. The cathode materials of lithium secondary batteries that are currently in use or are expected to be used include transition metal oxides such as LiCoO ₂ , Li _x NiO ₂ , Li _x Mn ₂ O ₄ , and LiM _x Co _1-x O ₂ , LiM _x CO And oxide solid solutions such as _1-x O ₂ (metals such as M = Ni, Co, Fe, Mn, and Cr). At present, the most widely used anode material is LiCoO ₂ , but since LiCoO ₂ is expensive (2 times Ni and 50 times Mn), it is urgent to develop other alternative materials. LiMn ₂ O ₄ has been studied because of its lowest cost, ease of manufacture, stability of electrolyte, stability in use, and harmlessness to human body.

LiMn ₂ O ₄ powder conditions for obtaining high anode performance are good crystallinity homogeneity, constant powder morphology with narrow particle distribution, large pore distribution, and the like. The above conditions can maintain the initial performance by suppressing the change in the microstructure during the charge and discharge, because the larger the pore distribution, the easier insertion or removal of lithium ions.

However, LiMn ₂ O _{4, which} has a spinel structure, has a three-dimensional structure, which has a high diffusion resistance during insertion or desorption of lithium ions, and has a low diffusion coefficient, and a discharge capacity due to mixing of lithium and manganese metal ions during manufacturing. Cycle characteristics are not good.

In the present invention, Li _x Mn ₂ O ₄ powder having a small amount of cation mixture having the above properties is prepared by the sol-gel method using glycolic acid as a chelating agent, and its physicochemical properties and battery charging Improved discharge characteristics

The most common method for producing LiMn ₂ O ₄ is a solid phase reaction method. This method is prepared by mixing and firing powders of carbonates and hydroxides of each element as a raw material. When mixing, there are a lot of impurities introduced from the ball mill, a heterogeneous reaction is likely to occur, it is difficult to obtain a uniform phase, it is difficult to control the size of the powder particles uniformly, and the sintering property is poor.

On the other hand, in the ceramic manufacturing field, a sol-gel method is being developed. This method forms a sol state by dissolving a metal alkoxide in a solvent and subjecting it to a sol state by hydrolysis and polymerization reaction, and gelation by changing the temperature, concentration and other conditions of the dispersion. The ceramic powder is obtained by drying and heat treatment. However, when the metal alkoxide is used as the metal precursor, the metal alkoxide price is too expensive, so the economic feasibility is not met. Therefore, in recent years, citric acid and pechini methods using metal nitrate, acetate, sulfate as metal precursors and citric acid and ethylene glycol as chelating agents have been widely studied. Since the physical properties of the prepared powders depend on the type of chelating agent, it is necessary to select an appropriate chelating agent. The advantage of using the sol-gel method is that it is easy to control the composition ratio, it is possible to obtain a high homogeneous product through the sol and gelation with high uniformity, less impurities inflow from the manufacturing process, relatively low firing temperature and short It is possible to manufacture the sintered body in time, and to manufacture in various forms such as spherical, film and fiber production.

LiMn ₂ O ₄ powder conditions for obtaining high anode performance are good crystllinity, homogeneity, constant powder morphology with narrow particle distribution. This is because the above conditions can maintain the initial performance by suppressing changes in the microstructure while the charge and discharge continue. In the present invention, to improve the economics and manufacturing method using a acetate as a metal precursor, glycolic acid as a chelating agent to make a gel precursor, the gel precursor at 200 ~ 900 ℃ for 5 to 30 hours inert gas or air Heat treatment in the atmosphere gives a Li _x Mn ₂ O ₄ powder. The prepared powder had a uniform particle size, and the microstructures, such as grain size, specific surface area, and cubic lattice constant, could be roughly adjusted according to the production conditions. In the present invention, instead of lithium acetate and manganese acetate, lithium nitrate or lithium hydroxide and manganese nitrate or gamma-manganese peroxide hydroxide (γ-MnOOH) may be used as the metal precursor. The ratio of lithium (Li) and manganese (Mn) in the lithium acetate (or lithium nitrate) and manganese acetate (manganese nitrate) used is preferably 1 to 1.1: 1. Li _x Mn ₂ O ₄ powder of the present invention is used as a positive electrode active material of a lithium ion battery or a lithium polymer battery that is a lithium secondary battery. The thin film can be manufactured by making the solution of Li _x Mn ₂ O ₄ of the present invention into a sol state. Composite cathode of the present invention (composite cathode) manufacturing a solid electrolyte (PAN, IM, LiCIO _4. Ethylene carbonate / propylene carbonate) and the conductive recognition acetylene black (acetylene black) was added to Li _x Mn ₂ O ₄ powder, and mixed with the slurry It is made of (slurry) and then coated on aluminum foil (Al foil), it can be prepared by drying.

The invention will be further illustrated by the following examples, which are intended to illustrate the invention and are not intended to limit the protection scope of the invention.

Example

Preparation of LiMn ₂ O ₄ Powder:

Li (CH ₃ COOH) · 2H ₂ O and Mn (CH ₃ COOH) ₂ · 4H ₂ O were quantified in a molar ratio of 1 to 1.1: 2 to dissolve distilled water, and then the molar ratio of glycolic acid to total metal ion sum was 0.5, 1.0, Aqueous solutions were made to 1.0 and 2.0 and mixed well with the above solution. The mixed solution was heated to 70-90 ° C. in a magnetic stirrer or dryer to form a sol, and then the sol was gradually heated to form a gel precursor. Transparent gel precursor synthesis was possible within the whole range of the molar ratio of glycolic acid total total metal ion tested in the present invention. This gel precursor was calcined in an air atmosphere at 250 to 800 ° C. for 5 to 30 hours to obtain a Li _x Mn ₂ O ₄ powder. The above manufacturing method is shown in FIG.

TG analysis and results:

The gel precursors prepared in this experiment were very transparent, indicating that the gel precursors were uniform. In order to investigate the transition process from gel precursors to ceramics, glycolic acid, a mixture of lithium acetate and manganese acetate (1: 2), and gel precursors vacuum dried at 80 ° C. were analyzed by TG and the results are shown in FIG. 2. In FIG. 2, (a) refers to glycolic acid, (b) refers to acetate mixed with lithium to manganese, and (c) means gel precursor. At this time, the gel precursor was prepared with a molar ratio of glycolic acid to total metal of 1: 5. Glycolic acid lost weight loss at 186 ° C, and the mixture of lithium acetate and manganese acetate (1: 2) evaporated water between 23 ~ 114 ° C, acetate decomposition at 200 ~ 295 ° C, and residual organic decomposition at 295 ~ 478 ° C. . The weight loss of the gel precursor occurred in three sections: 100 ~ 200 ℃, 200 ~ 313 ℃, and 313 ~ 387 ℃, and the weight loss was terminated at 378 ℃. The weight loss in the 100 ~ 200 ℃ range was due to glycolic acid decomposition in the gel precursor, the weight loss between 200 ~ 313 ℃ due to the acetate decomposition in the gel precursor, which is in good agreement with the weight reduction temperature of the metal acetate mixture. The weight loss between 313 and 387 ° C was due to the decomposition of the remaining organics. This weight loss is believed to be due to accelerated decomposition of acetate ions as glycolic acid decomposes during gel precursor decomposition, which acts as a fuel in the presence of metal ions to accelerate the decomposition of residual organics, causing violent oxidation and decomposition reactions. do. The weight loss in this section corresponds to 30 wt% of the weight of the gel precursor, which can be explained by the vertical weight loss in the TGA results.

XRD Pattern Analysis:

3 shows an X-ray diffraction pattern of a sample heat-treated under an air atmosphere at 250 to 800 ° C. for a gel precursor prepared with glycolic acid to total metal molar ratio of 1.5. In the case of a sample fired at 250 ° C., when the amorphous phase was 300 ° C., low crystalline spinel Li _1.03 Mn ₂ O ₄ was observed. As the firing temperature increased, the XRD peak showed sharp and high diffraction peaks, which resulted in a phase with high crystallinity of Li _1.03 Mn ₂ O ₄ . These results indicate that the sol-gel preparation of this study has a lower firing temperature and shorter manufacturing time than the solid phase reaction method through sintering at 650-850 ° C for 75-200 hours. This is because the sol-gel method using glycolic acid as a chelating agent was uniformly mixed with the starting sample in atomic size, and because the particle size was very small, the reaction rate of the formation of the structure was increased to improve the sinterability. 4 shows the lattice constant [a] of the cubic structure of the cubic spinel Li _1.03 M n ₂ O ₄ powder according to the firing temperature. The lattice constant [a] increased with the calcination temperature due to the decrease in the oxidation number of manganese cations. At low temperatures, since the Mn ⁴⁺ is stable, the lattice constant [a] decreases. Bellcore's Tarascon et al. Reported that in Li _x Mn ₂ O ₄ , the [a] value of a slow cooled (10 ° C / hr) sample with x greater than 1 was less than 8.23 kPa. In the case of more than 200 times safe discharge characteristics.

In the sample prepared in the present invention, the heat treatment was cooled to 30 ° C./hr, and the [a] values were 8.227 kPa and 8.2254 kPa at the firing temperatures of 750 ° C. and 800 ° C., respectively. 5 shows the non-target dependence of Li _1.03 Mn ₂ O ₄ powder (sample as shown in FIG. 3) according to the firing temperature. As the firing temperature increased, the specific surface area of the sample decreased linearly due to crystal growth due to sintering. The samples synthesized at 300 ° C and 800 ° C in this experiment were similar to the specific surface area of 3m ² / g of LiMn ₂ O ₄ which is commercially available at 33m ² / g and 3.8m ² / g, respectively.

The XRD pattern of the sample according to the glycolic acid-to-total metal molar ratio change of the gel precursor (glycolic acid to total metal mole ratio = 0.5, 1.0, 1.5, 2.0) is shown in FIG. At this time, the gel gel precursor was fired at 800 ° C. for 10 hours in an air atmosphere. The prepared samples were found to have a cubic spinel structure with a space group Fd3m regardless of the glycolic acid to total metal molar ratio change. Rietveld refinement (to calculate the a value) of the XRD data obtained in FIG. 6 was performed to further investigate the structural change of spinel Li _1.03 Mn ₂ O _{4 with} increasing glycolic acid amount. The calculation results are shown in FIG. 7, and the lattice constant a increases linearly with the amount of glycolic acid. 8 shows the non-target dependence of the amount of glycolic acid of Li _1.03 Mn ₂ O ₄ powder. Depending on glycol goats increased, the specific surface area of the sample was increased linearly, glycol acid to total metal molar ratio of 0.5, and a specific surface area of 2.0 when each sample was 3.9m ² / g and 2.55m ² / g.

SEM analysis:

SEM photographs of powders calcined for 10 hours at 300 ° C., 650 ° C., 750 ° C. and 800 ° C. in a gel precursor prepared with glycolic acid to total metal molar ratio 1.5 are shown in FIG. 9. The powder fired at 300 ° C. was composed of aggregated uniform spherical particles, and the average radius was 40 nm. As the firing temperature increased, the crystal growth rate of the powder increased, and the aggregated particles grew into one large particle. In the case of the powder heat-treated at 800 ° C., the aggregated particles grew to an average radius of 0.3 μm, and the particle distribution was fairly uniform. SEM photographs of powders calcined at 700 ° C. for 10 hours in a known atmosphere of a gel precursor prepared by glycolic acid to total metal molar ratios of 0.5 and 2.0 are shown in FIG. 10. The particle sizes of the powders prepared with glycolic acid to total metal molar ratios of 0.5 and 2.0 were 200 nm and 100 nm, respectively. Even at the same firing temperature, the amount of glycolic acid was varied to control the particle size of the sample.

Cathode Mixture Preparation:

To the Li _1.03 Mn ₂ O ₄ active material powder prepared above, 20 wt% and 8 wt% of ketjen black EC (conductive material, specific surface area) and Teflon (binder) were added to the cathode. A mixture was prepared. At this time, the Teflon binder was completely dissolved in water, the active material and the conductive material was added and mixed to make a dough, then applied to 316 stainless steel ex-met (USA), and dried by vacuum. As an electrolyte, a solution in which 1 M LiBF ₄ was dissolved in EC (ethylene carbonate) and DEC (diethyl carbonate) in a molar ratio of 1: 1 was used. EC and DEC used as a solvent were pretreated with a molecular sieve of 4 kPa activated for 2 hours at 350 ° C. to minimize water content. Both the comparative and counter electrodes used a lithium metal foil (Li foil) with a purity of 99.999%. Charging and discharging experiments according to the cycle were carried out in the 3.6 ~ 4.3V range with a constant current of 1mA / cm ² current density. Li / 1M LiBF ₄ -EC / DEC / Li _1.03 Mn ₂ O ₄ using Li _1.03 M n ₂ O ₄ prepared by heating the gel precursor prepared with glycolic acid total metal molar ratios of 0.75 and 1.5 at 760 ° C. for 24 hours. The discharge capacity according to the number of cycles at the charge / discharge current density of 1 mA / cm ² and the cutoff voltage of 3.6 to 4.3 V in the battery is shown in FIG. 11. For samples prepared with a glycolic acid-to-total metal molar ratio of 1.5, the initial discharge capacity appeared to be 128 mAh / g, gradually decreasing with the number of cycles and then 120 mAh / g at the 100th cycle. In addition, there was no capacity reduction since the 86th cycle. For samples prepared with a glycolic acid to total metal molar ratio of 0.75, the initial discharge capacity was 120 mAh / g and 107 mAh / g at the 100th cycle. The capacity reduction rates of the 100th cycle of samples prepared with glycolic acid to total metal molar ratios of 0.75 and 1.5 showed 12% and 6% of the initial capacity, respectively, taking into account the experiments with high current density (1mA / cm ² ). The capacity preservation characteristics were very good. Lithium polymer secondary battery is a solid electrolyte (PAN: 0.4g, 1MLiClO ₄ : 0.4g, Ethylene C arbonate) / propylene carbonate (Propylene Carbonate) in 59.5wt% LiMn ₂ O ₄ active material powder heat-treated at 760 ℃ for 24 hours ): 1.65g) 31.2 wt% and 9.3 wt% of acetylene black as a conductive material were added and mixed to make a sludge, followed by coating and drying on an aluminum foil to prepare a synthetic anode. The lithium polymer battery cell was prepared by bonding PAN, which is a solid polymer electrolyte, to a manufactured composite anode, and bonding a lithium electrode coated on copper to a solid polymer electrolyte. As the counter electrode, lithium metal having a purity of 99.999% was used. Charging of the cycling (cycling) · discharge experiments constant current at a current density change in the current density of 0.1mA / cm ₂ was carried out in 3.0 ~ 4.3V range of 0.1 ~ 4mA / cm ² constant current. Charge and discharge experiments were performed at room temperature. Charge / discharge in Li / Polymer electrolyte (PAN) / Li _1.03 Mn ₂ O ₄ cells using Li _1.03 Mn ₂ O ₄ prepared by heat-treating gel precursor prepared by glycolic acid to total metal molar ratio 1.0 at 760 ° C. for 24 hours The charge / discharge behavior and discharge capacity according to the number of cycles at the current density of 0.1 mA / cm ² and the cutoff voltage of 3.0 to 4.3 V are shown in FIG. 12. From the charge and discharge curves, the sample showed two discharge plateaues, characteristic of the manganese-spinel structure, representing 1/2 polarization of the difference between charge and discharge curves. Was maintained. The initial discharge capacity of the former was 134 mAh / g. The discharge capacity gradually decreased with the cycle number, and the 90th discharge capacity was 129 mAh / g, maintaining 96% of the initial capacity. 13 and 14 show current densities of 0.1, 0.2, 0.5, and Li in a polyelectrolyte (PAN) / Li _1.03 Mn ₂ O ₄ cell using Li _1.03 Mn ₂ O ₄ prepared by heat treatment at 760 ° C. for 24 hours. While changing to 1 mA / cm ² , the charge and discharge curves and the discharge capacity according to the number of cycles were shown, respectively. One-half of the charge and discharge curves in accordance with the primary side peak current density increase is increased (claim 13 degrees), a beam of about 130 mAh / g or more of capacity, current density up to 0.1 and 0.2 mA / cm ² is applied at 10 cycles There was little dose reduction. Discharge capacities of 121 and 78 mAh / g were applied at current densities of 0.5 (1 / 1.2C) and 1 mA / cm ² (1.7C), respectively. The initial discharge capacity was maintained when the cells were reapplied with current densities of 0.1 and 0.2 mA / cm ² .

In the conventional sol-gel method, citric acid or ethylene glycol was used as a chelating agent, but in the present invention, a pure phase Li _x Mn ₂ O ₄ powder was prepared using glycolic acid as a chelating agent. The battery test results showed excellent battery characteristics.

Simple modifications and variations of the present invention can be readily made by those skilled in the art, and all such modifications and changes can be seen to be included within the scope of the present invention.

Claims (8)

Gel precursors were prepared using lithium salt and manganese salt as metal precursors and glycolic acid as chelating agent; And heat treating the gel precursor at 200-900 ° C. for 5-30 hours in an inert gas or air atmosphere; Method for producing a Li _x Mn ₂ O ₄ (x = 1 ~ 1.1) powder used as a positive electrode active material of a lithium secondary battery, characterized in that it comprises a step. The method of claim 1, wherein the lithium (Li) salt is lithium acetate, lithium hydroxide or lithium nitrate, the manganese (Mn) salt is characterized in that the manganese acetate, gamma-manganese peroxide hydroxide (γ-MnOOH) or manganese nitrate Method for producing Li _x Mn ₂ O _{4 to be} . The method of claim 1, wherein the lithium (Li) for manganese method for producing Li _x Mn ₂ O ₄ for the composition ratio of the (Mn) ~ 1, characterized in that in the range of 1.1 to 1. The gel precursor is prepared by using the lithium salt and the manganese salt as a metal precursor and glycolic acid as a chelating agent, and the gel precursor is calcined at 200 ° C. to 900 ° C. for 5 to 30 hours in an inert gas or air atmosphere. Li _x Mn ₂ O ₄ powder used as a positive electrode active material of a lithium secondary battery prepared by. The method of claim 4, wherein the lithium (Li) salt is lithium acetate, lithium hydroxide or lithium nitrate, and the manganese (Mn) salt is manganese acetate, gamma-manganese peroxide hydroxide (γ-MnOOH) or manganese nitrate Li _x Mn ₂ O ₄ powder made.) The Li _x Mn ₂ O ₄ powder according to claim 4, wherein the composition ratio of lithium (Li) to manganese (Mn) is in the range of 1 to 1.1 to 1. Thin film prepared from the Li _x Mn ₂ O ₄ powder of any one of claims 4 to 6. A solid electrolyte (/ PAN, 1M LiCIO ₄ , ethylene carbonate / propylene carbonate) and acetylene black as a conductive material are added to the Li _x Mn ₂ O ₄ powder prepared according to any one of claims 1 to 3, A composite cathode prepared by mixing a slurry to make a slurry and then applying and drying on an aluminum foil.