KR101409191B1 - Manufacturing method of cathode active material for lithium secondary battery - Google Patents

Abstract

In the present invention, a lithium-boron oxide glass is coated on the surface of a lithium-nickel-manganese oxide in order to suppress elution of manganese (Mn), and the lithium-nickel-manganese oxide is LiNi _x Mn _2-x O ₄ (0 < _x ? 0.5). According to the present invention, it is possible to suppress the elution of manganese at high temperature, Life characteristics can be improved.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode active material for a lithium secondary battery,

The present invention relates to a method for producing a positive electrode active material, and more particularly, to a method for producing a positive electrode active material for a lithium secondary battery capable of suppressing elution of manganese at a high temperature to improve life characteristics of the lithium secondary battery.

Recently, there has been a rapid increase in the demand for rechargeable batteries which are used by repeatedly charging and discharging power from portable electronic devices such as mobile phones, personal digital assistants (PDA), laptop computers, digital cameras, camcorders, MP3 players, electric vehicles and electric bicycles . Particularly, performance of a product such as a portable electronic device is dependent on a secondary battery, which is a core component, and development of a high performance secondary battery is required. The characteristics required for such a secondary battery include various aspects such as charge / discharge characteristics, life characteristics, high rate characteristics, and stability at high temperatures.

Among secondary batteries, lithium secondary batteries are the most popular because they have high voltage and high energy density. Lithium secondary battery using spinel composite oxide as a cathode active material is the most remarkable battery because of its high energy density due to high voltage.

Most of the currently available lithium _secondary batteries use LiCoO ₂ as the anode and carbon as the cathode. However, the use of cobalt (Co) used as a cathode active material is required to develop a new replaceable cathode active material because it has a low storage capacity, high cost, toxicity to human body and environmental pollution problem.

LiNiO ₂ , LiCo _x Ni _{1 - x} O ₂ , LiMn ₂ O ₄ , and the like can be cited as the cathode active materials which are actively studied at present. LiNiO ₂ having a layered structure is not only difficult to synthesize a material having a stoichiometric ratio but also has a problem in thermal stability. LiMn ₂ O ₄ having a spinel structure has an advantage of using manganese (Mn) as a base material, but it has a structure variation called Jahn-Teller distortion due to Mn ^{3 +} and a structure using a negative electrode as graphite The high temperature lifetime characteristics due to Mn ^{2 +} elution are not good.

In addition, a general method for producing a cathode active material is a solid-phase reaction method. In this method, a cathode active material is manufactured through several steps of mixing and firing a carbonate or hydroxide of each constituent element as a raw material. However, this method has a problem in that impurities flow from the ball mill in the mixing process and the heterogeneous reaction tends to occur, making it difficult to obtain a uniform phase and a long manufacturing time. In addition, the manganese oxidation number of 3+ generated during firing are yarn-induced distortion and a telescopic, Mn ^{+ 3} oxide of manganese is present in this case is used as a cathode active material for a lithium secondary battery, the crystal of the positive electrode active material, depending on the charge-and-discharge cycle is repeated to structure And the lifetime characteristics of the battery may be deteriorated.

A problem to be solved by the present invention is to provide a lithium secondary battery, Which can improve the lifetime characteristics of a lithium secondary battery.

In the present invention, a lithium-boron oxide glass is coated on the surface of a lithium-nickel-manganese oxide in order to suppress elution of manganese (Mn), and the lithium-nickel-manganese oxide is LiNi _x Mn _{2- x} O ₄ (0 < _x ? 0.5).

The lithium-boron oxide glass may be made of an amorphous LiO ₂ -B ₂ O ₃ oxide.

The lithium-boron oxide glass coated on the surface of the lithium-nickel-manganese oxide preferably comprises 0.01 to 1.5 parts by weight based on 100 parts by weight of the lithium-nickel-manganese oxide.

The present invention also provides a lithium _secondary battery comprising a lithium battery having a spinel crystal structure, wherein at least one lithium source selected from lithium sulfate (Li ₂ SO ₄ ) and lithium chloride (LiCl) and a boron source composed of boron oxide (B ₂ O ₃ ) - preparing a nickel-manganese oxide (LiNi _x Mn _2-x O ₄ (0 < _x ? 0.5)), dissolving the lithium source and the boron source in a solvent, and mixing the lithium source and the boron source Nickel-manganese oxide is immersed in a solution in which the lithium-nickel-manganese oxide is dissolved and dried, and the dried product is heat-treated at a temperature of 400 to 700 ° C so that the lithium-boron oxide glass is coated on the surface of the lithium- Thereby obtaining a positive electrode active material. The present invention also provides a method for producing a positive electrode active material for a lithium secondary battery.

The lithium source and the boron source are preferably dissolved in the solvent so that lithium (Li) and boron (B) have a molar ratio of 1: 2.

Method for producing the cathode active material for a lithium secondary battery may further include the step of crushing the lithium source and the boron source prior to dissolve the lithium source and the boron source in the solvent, the solvent is water (H ₂ O ), And the dissolution is preferably carried out at a temperature of 40 to 80 캜.

Wherein the lithium-boron-based oxide glass coated on the surface of the lithium-nickel-manganese oxide is 0.01 to 1.5 parts by weight based on 100 parts by weight of the lithium-nickel-manganese oxide, the lithium source, the boron- - It is preferable to control the content of manganese oxide.

The step of preparing the lithium-nickel-manganese oxide comprises preparing a lithium source, a nickel source and a manganese source such that a molar ratio of Li: Ni: Mn is 1: x: 2-x ((0 & (LiNi _x Mn _{2- y} M ₂ O _2), and the resulting lithium source, a nickel source and a manganese source in a solvent, adding sucrose to the dissolved product, drying the resultant, _x O ₄ (0 < _x &lt; 0.5)), and the lithium source may be at least one material selected from lithium sulfate (Li ₂ SO ₄ ) and lithium chloride (LiCl) the source of nickel sulfate (NiSO ₄₎ and nickel chloride (NiCl ₂₎ may be one or more materials that are selected from, the manganese source may be one or more materials that are selected from manganese sulfate (MnSO ₄₎ and manganese chloride (MnCl ₂₎ have.

The solvent may be water (H ₂ O), and the dissolution is preferably carried out at a temperature of 40 to 80 ° C.

The heat treatment is preferably performed at a temperature of 700 to 900 DEG C, and may further include annealing at a temperature of 400 to 600 DEG C after the heat treatment.

According to the present invention, it is possible to suppress the elution of manganese at high temperature, Life characteristics can be improved.

In the case of using a cathode active material composed of lithium-nickel-manganese oxide surface-treated with lithium-boron oxide glass, the reduction rate of the discharge capacity of the lithium secondary battery in the charge-discharge test was superior to that of the conventional cathode active material, The discharge capacity was also excellent at 100 to 120 mAh / g even after 50 repetitive charge / discharge cycles.

Figure 1 is a lithium prepared according to Experimental Example 1 - Scanning electron microscopy of the manganese oxide _{(LiNi 0 .5 Mn 1 .5 O} 4) - nickel; a (scanning electron microseope SEM) photo.
FIG. 2 is a scanning electron microscope (SEM) photograph of a lithium-nickel-manganese oxide coated with lithium-boron oxide glass according to Experimental Example 2. FIG.
Figure 3 Experimental Example 1 The lithium-prepared according to the-nickel-manganese oxide _{(LiNi 0 .5 Mn 1 .5 O} 4) X- ray diffraction, (in Fig. 3 (a)) (X- ray diffraction XRD) pattern Ray diffraction (XRD) pattern (FIG. 3 (b)) of a lithium-nickel-manganese oxide coated with lithium-boron oxide glass according to Experimental Example 2. FIG.
FIG. 4 is a charge / discharge curve showing a specific capacity according to a voltage.
FIG. 5 is a graph of a lifetime characteristic showing a discharge capacity according to the number of charge / discharge cycles.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it should be understood that the following embodiments are provided so that those skilled in the art will be able to fully understand the present invention, and that various modifications may be made without departing from the scope of the present invention. It is not.

Conventional lithium-nickel-manganese oxides lead to deterioration of lifetime characteristics of lithium secondary batteries due to the elution of manganese at high temperatures. It is possible to suppress the elution of manganese at a high temperature, In order to improve the lifespan characteristics, the present invention is characterized in that lithium-boron oxide glass is coated on the surface of the lithium-nickel-manganese oxide surface to modify the surface thereof, so that the lifetime characteristics at a high temperature (for example, 50 to 70 ° C) This positive electrode active material for an excellent lithium secondary battery is presented.

The cathode active material for a lithium secondary battery according to the preferred embodiment of the present invention is a lithium-nickel-manganese oxide (LiNi _x Mn _{2 -x} O ₄ (0 < _x &lt; 0.5)) surface is coated with a lithium-boron oxide glass. By coating the surface of the lithium-nickel-manganese oxide with a lithium-boron oxide glass, the lifetime characteristics at high temperature (for example, 50 to 70 ° C) can be improved compared with lithium-nickel-manganese oxide not coated with lithium- Can be improved.

The lithium-boron oxide glass is made of an amorphous LiO ₂ -B ₂ O ₃ oxide.

The lithium-boron oxide glass coated on the surface of the lithium-nickel-manganese oxide preferably comprises 0.01 to 1.5 parts by weight based on 100 parts by weight of the lithium-nickel-manganese oxide.

Hereinafter, a method of manufacturing a cathode active material for a lithium secondary battery according to a preferred embodiment of the present invention will be described.

A lithium-nickel-manganese oxide (LiNi _x Mn _{2 -x} O ₄ (0 < _x ? 0.5)) having a spinel crystal structure is prepared.

To this end, Li: the molar ratio of Mn 1:: Ni x:. 2-x ((0 < x≤0.5 to achieve a) Prepare a lithium source, manganese source, and a nickel source wherein the lithium source is lithium sulfate (Li ₂ SO ₄ ) and lithium chloride (LiCl) may be one or more materials that are selected from the nickel sources are nickel sulfate (NiSO ₄₎ and nickel chloride (NiCl ₂₎ may be one or more materials that are selected from, the manganese source is manganese sulfate It may be (MnSO ₄₎ and manganese chloride (MnCl ₂₎ 1 or more materials that are selected from.

The prepared lithium source, nickel source and manganese source are dissolved in a solvent. The lithium source, the nickel source and the manganese source are preferably dissolved in the solvent so as to form a molar ratio of 1: x: 2-x (0 <x? 0.5). The solvent may be water (H ₂ O) The dissolution is preferably performed at a temperature of 40 to 80 DEG C. The dissolution in the above temperature range has the effect of completely dissolving the lithium source, nickel source and manganese source in the solvent and reducing the dissolution time.

Sucrose is added to the dissolved product and dried. Impurities such as impurities NiO _x and LiNiO _x are easily generated when the lithium-nickel-manganese oxide (LiNi _x Mn _{2 -x} O ₄ (0 < _x ≦ 0.5)) is heat-treated. Since sucrose is added to perform a subsequent heat treatment step, impurities can be prevented from being formed by reacting with CO ₂ before the impurities are formed and blowing them out with the gas. The drying is preferably performed at a temperature of 100 to 150 캜 and at a speed of 10 to 500 rpm for 1 to 72 hours with stirring. The drying causes the solvent to evaporate and be removed.

The dried product is heat-treated to obtain a lithium-nickel-manganese oxide (LiNi _x Mn _{2 -x} O ₄ (0 < _x ? 0.5)). The heat treatment is preferably performed at a temperature of 700 to 900 DEG C for 1 to 48 hours. Also, the heat treatment is preferably performed in an oxidizing atmosphere such as air or oxygen.

And annealing at a temperature of 400 to 600 DEG C after the heat treatment. The annealing is preferably performed for 1 to 48 hours in an oxidizing atmosphere such as air or oxygen. Nickel-manganese oxide (LiNi _x Mn _{2 -x} O ₄ (0 < _x ? 0.5)) having a stable crystal structure can be obtained by performing annealing.

At least one lithium source selected from lithium sulphate (Li ₂ SO ₄ ) and lithium chloride (LiCl) and a boron source composed of boron oxide (B ₂ O ₃ ) are prepared. The lithium source and the boron source are prepared so that lithium (Li) and boron (B) form 1: 2 in a molar ratio.

The prepared lithium source and the boron source are dissolved in a solvent. The lithium source and the boron source are preferably dissolved in the solvent so that lithium (Li) and boron (B) have a molar ratio of 1: 2. The solvent may be water (H ₂ O), and the dissolution is preferably carried out at a temperature of 40 to 80 ° C. By dissolving in the above temperature range, there is an effect that the lithium source and the boron source are completely dissolved in the solvent and the dissolution time is reduced.

The method may further include a step of pulverizing the lithium source and the boron source before the lithium source and the boron source are dissolved in the solvent. By pulverizing the lithium source and the boron source, the lithium source and the boron source can be easily dissolved in the solvent and the dissolution time can be reduced.

The milling may be performed by ball milling, jet milling or the like. As a specific example of the milling process, the ball milling process will be described. A lithium source and a boron source are charged into a ball milling machine, and the milling machine is rotated at a constant speed using a ball mill. The size of the balls, the milling time, the rotation speed of the ball miller, and the like are adjusted so as to be crushed to the target particle size. As the milling time increases, the particle size of the lithium source and the boron source gradually decreases, thereby increasing the specific surface area. The balls used for ball milling can be ceramic balls such as alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), and the balls may be all the same size or may be used together with balls having two or more sizes It is possible. The size of the ball, the milling time, and the rotation speed per minute of the ball mill are adjusted. For example, the size of the ball is set in the range of about 1 to 30 mm, and the rotation speed of the ball mill is about 50 to 500 rpm And ball milling can be performed for 1 to 50 hours.

The lithium-nickel-manganese oxide (LiNi _x Mn _{2 -x} O ₄ (0 < _x ? 0.5)) is immersed in a solution in which the lithium source and the boron source are dissolved and dried. The drying is preferably performed at a temperature of 40 to 80 캜 for 1 to 72 hours. It is preferable to control the content of the lithium-nickel-manganese oxide so that the lithium-boron oxide glass coated on the surface of the lithium-nickel-manganese oxide is 0.01 to 1.5 parts by weight based on 100 parts by weight of the lithium-nickel- Do.

The dried resultant is heat-treated at a temperature of 400 to 700 占 폚 to obtain a cathode active material in which lithium-boron oxide glass is coated on the surface of lithium-nickel-manganese oxide. In the process described above, the lithium-boron-based oxide glass coated on the surface of the lithium-nickel-manganese oxide is added in an amount of 0.01 to 1.5 parts by weight based on 100 parts by weight of the lithium-nickel- - nickel-manganese oxide content of the nickel-manganese oxide.

The cathode active material coated with the lithium-boron-based oxide glass on the surface of the lithium-nickel-manganese oxide can be used as the anode of the lithium secondary battery. Hereinafter, a method of manufacturing a positive electrode of a lithium secondary battery using the positive electrode active material will be described.

A positive electrode active material, a conductive material, a binder and a solvent are mixed to prepare a composition for a positive electrode for a lithium secondary battery.

The composition for a lithium secondary battery positive electrode comprises a positive electrode active material, 2 to 20 parts by weight of a conductive material per 100 parts by weight of the positive electrode active material, 2 to 20 parts by weight of a binder with respect to 100 parts by weight of the positive electrode active material, 1 to 300 parts by weight of a solvent. Since the composition for a positive electrode for a lithium secondary battery is in a kneading state, it may be difficult to uniformly mix (completely disperse). It is preferable to use a mixer such as a planetary mixer for a predetermined time (for example, 10 minutes to 12 hours) When the mixture is stirred, a composition for a positive electrode of a lithium secondary battery suitable for electrode production can be obtained. A mixer such as a planetary mixer enables the preparation of a uniformly mixed composition for a cathode of a lithium secondary battery.

The binder may be selected from the group consisting of polytetrafluoroethylene (PTFE), polyvinylidenefluoride (PVDF), carboxymethylcellulose (CMC), polyvinyl alcohol (PVA), polyvinyl butyral vinyl butyral (PVB), poly-N-vinylpyrrolidone (PVP), styrene butadiene rubber (SBR), polyamide-imide, polyimide One or more selected ones may be used in combination.

The conductive material is not particularly limited as long as it is an electron conductive material which does not cause a chemical change. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, Super-P black, carbon fiber, , Metal powder such as aluminum and silver, or metal fiber.

The solvent may be an organic solvent such as ethanol (EtOH), acetone, isopropyl alcohol, N-methyl pyrrolidone (NMP), propylene glycol (PG) or water.

A lithium secondary battery positive electrode composition in which a positive electrode active material, a binder, a conductive material and a solvent are mixed is formed into an electrode form, or the lithium secondary battery positive electrode composition is coated on a metal foil to form an electrode, The positive electrode composition is rolled into a sheet form and attached to a metal foil to form an electrode, and the resultant electrode is dried at a temperature of 100 to 350 DEG C to form a positive electrode of the lithium secondary battery.

An example of forming a positive electrode of a lithium secondary battery will be described in more detail. The composition for a positive electrode of a lithium secondary battery can be pressed and formed by using a roll press molding machine. The roll press molding machine aims at improving the electrode density through rolling and controlling the thickness of the electrode. The roll press molding machine includes a controller capable of controlling the thickness and the heating temperature of the rolls and rolls at the upper and lower ends, the winding &Lt; / RTI &gt; As the electrode in the roll state passes the roll press, the rolling process is carried out and the roll is rolled again to complete the electrode. At this time, the pressing pressure of the press is preferably 5 to 20 ton / cm 2, and the roll temperature is preferably 0 to 150 ° C. The composition for a positive electrode of a lithium secondary battery that has undergone the above press-bonding process is subjected to a drying process. The drying process is carried out at a temperature of 100 ° C to 350 ° C, preferably 150 ° C to 300 ° C. If the drying temperature is less than 100 ° C, evaporation of the solvent is difficult, which is not preferable, and oxidation of the conductive material may occur during drying at a high temperature exceeding 350 ° C, which is not preferable. Therefore, the drying temperature is preferably 100 占 폚 or more and not exceeding 350 占 폚. The drying process is preferably carried out at the above temperature for about 10 minutes to 6 hours. Such a drying process improves the strength of the lithium secondary battery anode by drying (solvent evaporation) the composition for the anode of the lithium secondary battery and binding the powder particles.

Another example of forming a positive electrode of a lithium secondary battery will be described below. The composition for the positive electrode of the lithium secondary battery is prepared by forming a metal foil (e.g., Ti foil, Al foil, Al foil, metal foil), or the lithium secondary battery positive electrode composition may be rolled into a sheet state (rubber type) and attached to a metal foil to produce an anode shape. The aluminum etched foil means that the aluminum foil is etched in a concavo-convex shape. The cathode shape after the above-mentioned process is subjected to a drying process. The drying process is carried out at a temperature of 100 ° C to 350 ° C, preferably 150 ° C to 300 ° C. If the drying temperature is less than 100 ° C, evaporation of the solvent is difficult, which is not preferable, and oxidation of the conductive material may occur during drying at a high temperature exceeding 350 ° C, which is not preferable. Therefore, the drying temperature is preferably 100 占 폚 or more and not exceeding 350 占 폚. The drying process is preferably carried out at the above temperature for about 10 minutes to 6 hours. This drying process improves the strength of the positive electrode of the lithium secondary battery by drying the composition for the positive electrode of the lithium secondary battery (solvent evaporation) and binding the powder particles.

The lithium secondary battery anode manufactured as described above may be usefully applied to a lithium secondary battery of a desired type such as a coin cell.

Hereinafter, experimental examples according to the present invention will be presented, and the present invention is not limited to the following experimental examples.

<Experimental Example 1>

Lithium-nickel-manganese oxide, LiNi _{0 .5} Mn _{1 .5} to manufacture O ₄ Li: the molar ratio of Mn 2:: Ni 1: 3 ( or 1: 0.5: 1.5) to achieve lithium nitrate (LiNO ₃₎ 0.02 mol of nickel nitrate (Ni (NO ₃ ) ₂ .6H ₂ O), and 0.03 mol of manganese nitrate (Mn (NO ₃ ) ₂ .6H ₂ O) were prepared.

The prepared lithium nitrate (LiNO ₃ ), nickel nitrate (Ni (NO ₃ ) ₂揃 6H ₂ O) and manganese nitrate (Mn (NO ₃ ) ₂揃 6H ₂ O) were placed in a 250 ml container, Lt; RTI ID = 0.0 &gt; 60 C &lt; / RTI &gt; for 24 hours.

Lithium nitrate (LiNO _3), nickel nitrate _{(Ni (NO 3) 2 ·} 6H 2 O) and manganese nitrate _{(Mn (NO 3) 2 ·} 6H 2 O) is 1 mole of sucrose (3.424g) was dissolved in a solution Followed by drying for 24 hours with stirring at a rate of about 200 rpm at 120 ° C.

The dried product was heat-treated at a temperature of 800 ° C. for 10 hours, annealed at a temperature of 600 ° C. for 10 hours, and cooled to 3 ° C. per minute to obtain a lithium-nickel-manganese oxide (LiNi _{0 .5} Mn _{1 . 5} O ₄ ) was synthesized.

<Experimental Example 2>

To prepare lithium-boron oxide glass, 0.01 mol of lithium hydroxide (LiOH) and 0.02 mol of boric acid (H ₃ BO ₃ ) were prepared.

The prepared lithium hydroxide (LiOH) and boric acid (H ₃ BO ₃ ) were placed in a mortar and ground for 1 hour using a mortar.

Crushed lithium hydroxide (LiOH) and boric acid (H ₃ BO ₃ ) were placed in a 250 ml container, and 50 ml of ultrapure water was added thereto, followed by dissolving at a temperature of 60 ° C for 3 hours.

Lithium hydroxide (LiOH) and boric acid (H ₃ BO ₃₎ The lithium synthesized in Experimental Example 1 in the dissolved solution-nickel-then immersed into a manganese oxide _{(LiNi 0 .5 Mn 1 .5 O} 4), 60 ℃ &Lt; / RTI &gt;

The dried product was heat-treated at a temperature of 600 ° C for 10 hours to obtain a cathode active material coated with lithium-boron oxide glass on the surface of lithium-nickel-manganese oxide.

<Experimental Example 3>

0.8 g of the cathode active material coated with lithium-nickel-manganese oxide on the surface of the lithium-boron oxide glass according to Experimental Example 2, 0.1 g of super-P as a conductive material, 0.1 g of polyvinylidenefluoride PVDF) and 1.5 g of N-methylpyrrolidone (NMP) as a solvent were uniformly mixed to form a composition for a lithium secondary battery positive electrode.

The composition for the positive electrode of the lithium secondary battery was uniformly compressed at a pressure of 5 ton by using a hydraulic machine (Ex-met), and vacuum dried at 120 ° C to prepare a positive electrode of a lithium secondary battery.

1.15 moles of LiPF ₆ in a mixed solvent of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate mixed at a volume ratio of 3: 3: 4 was used as a separator, and the positive electrode of the lithium secondary battery and the lithium foil were used as counter electrodes. Coin cell of 2032 standard was manufactured according to a conventional manufacturing process of a lithium secondary battery using a solution as an electrolyte.

Figure 1 Experimental Example 1 The lithium-prepared according to the-nickel-manganese oxide _{(LiNi 0 .5 Mn 1 .5 O} 4) scanning electron microscope; and (scanning electron microseope JEOL, Japan, JSM-7000F) pictures, 2 Is a scanning electron micrograph of a lithium-nickel-manganese oxide coated with lithium-boron oxide glass according to Experimental Example 2. FIG.

1 and 2, it can be seen that the lithium-nickel-manganese oxide prepared according to Experimental Example 1 has a particle size of 0.2 to 5 μm. It can be seen that the particle size of the lithium-nickel-manganese oxide coated with lithium-boron oxide glass according to Experimental Example 2 is not different from the particle size of the lithium-nickel-manganese oxide prepared according to Experimental Example 1. [

Figure 3 Experimental Example 1 The lithium-prepared according to the-nickel-manganese oxide _{(LiNi 0 .5 Mn 1 .5 O} 4) X- ray diffraction, (in Fig. 3 (a)) (X- ray diffraction XRD) pattern Ray diffraction (XRD) pattern (FIG. 3 (b)) of a lithium-nickel-manganese oxide coated with lithium-boron oxide glass according to Experimental Example 2. FIG. X-ray diffraction was measured using a D / Max-2500 manufactured by Rigaku, Japan.

3, lithium-nickel-manganese oxide prepared according to Experimental Example 1 and lithium-nickel-manganese oxide coated with lithium-boron oxide glass according to Experimental Example 2 have the same crystal phase. From this, it can be seen that the lithium-boron oxide glass does not have a crystalline phase but an amorphous phase.

In order to evaluate the characteristics of the lithium secondary battery prepared according to Experimental Example 3 Electrochemical analysis apparatus (Maccor, USA, S-4000 ) potential region of 3.5 ~ 4.9V at 65 ℃ using and current of 0.7mA / cm ² Charge and discharge experiments were carried out under the density conditions. FIG. 4 is a charge / discharge curve showing a specific capacity according to a voltage, and FIG. 5 is a graph of a lifetime characteristic showing a discharge capacity according to the number of charge / discharge cycles. 4 and 5, (a) shows the case of lithium-nickel-manganese oxide produced according to Experimental Example 1, and (b) shows the case of lithium-nickel-manganese oxide coated with lithium- Oxide.

Referring to FIG. 4, the lithium-nickel-manganese oxide coated with lithium-boron oxide glass according to Experimental Example 2 was subjected to a surface treatment (coating) with lithium-boron oxide glass, The overall initial discharge capacity was reduced by about 5 mAh / g compared to manganese oxide.

Referring to FIG. 5, in the case of the lithium-nickel-manganese oxide of Experimental Example 1 in which the surface treatment with lithium-boron oxide glass was not performed, the reduction rate of the discharge capacity at high temperature (65 ° C) The lithium-nickel-manganese oxide coated with lithium-boron oxide glass showed a reduction rate of the discharge capacity at a high temperature (65 ° C) as the first charge / discharge and one discharge Compared with about 87% of the capacity.

In the case of using a cathode active material composed of a lithium-nickel-manganese oxide surface-treated with lithium-boron oxide glass, the reduction rate of the discharge capacity of the lithium secondary battery in the charge-discharge test was higher than that of the lithium- Manganese oxide, and its discharge capacity was excellent at 100 to 120 mAh / g after 50 repetitive charge / discharge cycles.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, This is possible.

Claims (10)

delete delete delete At least one first lithium source selected from lithium sulphate (Li ₂ SO ₄ ) and lithium chloride (LiCl) and a boron source composed of boron oxide (B ₂ O ₃ ) are prepared and lithium-nickel-manganese Oxide (LiNi _x Mn _2-x O ₄ (0 < _x ? 0.5));
Dissolving the first lithium source and the boron source in water (H ₂ O);
Immersing the lithium-nickel-manganese oxide in a solution in which the first lithium source and the boron source are dissolved, followed by drying; And
Treating the dried resultant at a temperature of 400 to 700 DEG C to obtain a cathode active material coated with lithium-boron-based oxide glass on the surface of lithium-nickel-manganese oxide,
The step of preparing the lithium-nickel-manganese oxide comprises:
Preparing a second lithium source, a nickel source and a manganese source such that a molar ratio of Li: Ni: Mn is 1: x: 2-x ((0 <
Dissolving the prepared second lithium source, nickel source and manganese source in a solvent;
Adding sucrose to the dissolved product and drying; And
Treating the dried product to obtain a lithium-nickel-manganese oxide (LiNi _x Mn _2-x O ₄ (0 < _x ? 0.5)
The second lithium source is at least one material selected from lithium sulfate (Li ₂ SO ₄ ) and lithium chloride (LiCl)
The nickel source is one or more materials that are selected from nickel sulfate (NiSO ₄₎ and nickel chloride (NiCl _2),
Wherein the manganese source is at least one material selected from manganese sulfate (MnSO ₄ ) and manganese chloride (MnCl ₂ ).
The lithium secondary battery according to claim 4, wherein the first lithium source and the boron source are dissolved in water (H ₂ O) so that a molar ratio of lithium (Li) and boron (B) is 1: A method for producing a cathode active material.
The method of claim 4, further comprising the step of grinding the first lithium source and the boron source to the first lithium source and the boron source before being dissolved in the water (H ₂ O),
Wherein the dissolution is performed at a temperature of 40 to 80 캜.
The lithium secondary battery according to claim 4, wherein the lithium-boron oxide glass coated on the surface of the lithium-nickel-manganese oxide is 0.01 to 1.5 parts by weight based on 100 parts by weight of the lithium-nickel- Wherein the content of the boron oxide and the lithium-nickel-manganese oxide is controlled.
delete 5. The method of claim 4, wherein the solvent is water (H ₂ O), and the dissolution is performed at a temperature of 40 to 80 ° C.
5. The method of claim 4, wherein the heat treatment is performed at a temperature of 700 to 900 DEG C, and annealing is performed at a temperature of 400 to 600 DEG C after the heat treatment.

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