KR20100061349A - Positive electrode for lithium ion secondary battery and lithium ion secondary battery including same - Google Patents

Abstract

PURPOSE: A positive electrode for a secondary lithium battery is provided to keep positive electrode active material in stable state when the battery is charged/discharged at a high temperature and a high pressure and to obtain excellent cycle properties. CONSTITUTION: A positive electrode for a secondary lithium battery includes a lithium manganese-based compound core and a heat-resistant polymer which is located on the lithium manganese-based compound core. The heat-resistant polymer has a glass transition temperature(Tg) of 80-400°C. The heat- resistant polymer is selected from a group comprising a polyamide resin, a polyimide resin, a polyamide-imide resin, a polyacrylonitrile resin, a polysulfone resin, a polybenzoimidazole resin, a polytetrafluoroethylene resin, or their copolymers.

Description

A positive electrode for a lithium ion secondary battery, and a lithium ion secondary battery including the same {POSITIVE ELECTRODE FOR LITHIUM ION SECONDARY BATTERY AND LITHIUM ION SECONDARY BATTERY INCLUDING SAME}

It relates to a positive electrode for a lithium ion secondary battery and a lithium ion secondary battery comprising the same.

Recently, a higher capacity is required for a lithium ion secondary battery that can be used in a mobile phone or a notebook computer. To realize such a high capacity and high energy density, a high charging voltage is set to improve the utilization rate of the positive electrode to achieve high capacity. Attempts are being made.

For example, when a lithium manganese oxide such as LiMn ₂ O ₄ is used as the positive electrode active material, it is precipitated into metal manganese by the insertion reaction of lithium ions accompanying charge and discharge. As described above, when metal manganese is deposited and accumulated in the negative electrode, the cycle characteristics of the lithium ion secondary battery are degraded due to breakage of the separator or deterioration of the negative electrode.

As such, when the metal is eluted from the positive electrode active material, the metal is deposited on the negative electrode or the separator is oxidized, thereby deteriorating the lithium ion secondary battery. Since the dissolution of such transition metal is remarkable at high voltage and high temperature, the degradation accompanying the dissolution of the transition metal is more remarkable at high voltage and high temperature. Due to the deterioration, the impedance (resistance) of the lithium ion secondary battery is increased, and the cycle characteristics are lowered.

In order to solve the above-mentioned problem, the method of suppressing deterioration of electrolyte solution, a negative electrode, or a separator was tried through the aramid resin (meaning an wholly aromatic polyamide resin) layer between a positive electrode and a separator. However, the above method cannot prevent the metal from eluting from the positive electrode active material inside the positive electrode not in contact with the aramid resin layer.

One aspect of the present invention is to provide a positive electrode for a lithium ion secondary battery that can maintain a positive electrode active material in a stable state even when charging and discharging under high voltage and high temperature, and can exhibit excellent cycle characteristics.

Another aspect of the present invention is to provide a lithium ion secondary battery comprising the positive electrode.

The positive electrode for a lithium ion secondary battery according to an aspect of the present invention is used in a lithium ion secondary battery including a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material, the positive electrode is a lithium manganese compound core and And a heat resistant polymer positioned on the lithium manganese compound core, wherein the heat resistant polymer has a glass transition temperature (Tg) of about 80 to about 400 ° C.

The heat resistant polymer having a glass transition temperature (Tg) of about 80 to about 400 ° C. may include polyamide (PA) resin, polyimide (PI) resin, polyamideimide (PAI) resin, polyacrylonitrile (PAN) resin, poly It may be selected from the group consisting of sulfone (PS) resin, polybenzoimidazole (PBI) resin, polytetrafluoroethylene (PTFE) resin, or copolymers thereof, and combinations thereof. The polyamide resin may be a wholly aromatic polyamide-based resin. The heat resistant polymer resin content may be about 0.01 part by weight to about 3 parts by weight based on 100 parts by weight of the lithium manganese compound.

When positioning the heat resistant polymer, the average thickness of the heat resistant polymer layer may be about 0.002 to about 0.5 μm.

In addition, according to another aspect of the present invention, a cathode for a lithium ion secondary battery includes a lithium manganese compound core and a heat resistant polymer and an inorganic metal compound positioned on the manganese compound core, and the heat resistant polymer has a glass transition temperature of about 80 degrees. To about 400 ° C.

The heat resistant polymer is polyamide (PA) resin, polyimide (PI) resin, polyamideimide (PAI) resin, polyacrylonitrile (PAN) resin, polysulfone (PS) resin, polybenzoimidazole (PBI) resin , Polytetrafluoroethylene (PTFE) resins or copolymers thereof, and combinations thereof. The polyamide resin may be a wholly aromatic polyamide-based resin. The heat resistant polymer resin content may be about 0.01 part by weight to about 3 parts by weight based on 100 parts by weight of the lithium manganese compound.

The inorganic metal compound may be selected from the group consisting of oxides, hydroxides, nitrides, halides, sulfides, and combinations thereof. The metal of the inorganic metal compound may be selected from Al, Ti, Zr, Mg, Si, Li, Zn, La, Nb, Ta, Ge, Y, Se, B, or a combination thereof. The inorganic metal compound is Li _{2 + 2x} Zn _1-x GeO ₄ (where 0 <x <1), Li _4-3x Ga _x GeO ₄ (here 0 <x <1), La _{2 / 3-x} Li _3x TiO ₃ (0..03≤x≤0.167), La _{1 / 3-x} Li _3x TaO ₃ (0.025≤x≤0.167), La _{1 / 3-x} Li _3x NbO ₃ (0≤x≤0.06), La _1.3 Li _1.7 Al _0.3 (PO ₄ ) ₃ , LiAlTa (PO ₄ ) ₃ , LiAl _0.4 Ge _1.6 (PO ₄ ) ₃ , Li _1.4 Ti _1.6 Y _0.4 (PO ₄ ) ₃ , Li ₂ OSeO ₂ B ₂ O ₃ , LiCl-Li _1.4 M ₂ (PO ₄ ) ₃ , where M is Al, Ti, Ge or mixtures thereof, Li _x PO _y N _z (where x = 2.9, y = 3.3, z = 0.46), Li _x BO _y N _z (where 0 <x <1, 0 < y <1, 0 <z <1), Li 2 S · P 2 O 5, Li 2 S · SiS 2, Li 2 S · SiS 2 · Li x MO ₄ (wherein M is Si, P, Ge or a mixture thereof, 0 <x <1), Li 2 S · SiS 2 · Li 3 PO 4, Li 2 S · SiS 2 · xMS y ( wherein M is Sn, Ta, Ti or mixtures thereof, 0 <x <1), Li ₂ S.SiS ₂ .Li ₃ N, Li ₃ N.SiS ₂ , or a combination thereof.

The mixing ratio of the heat resistant polymer and the inorganic metal compound may be 5 to 50 parts by weight of the heat resistant polymer to 95 to 50 parts by weight of the inorganic metal compound. When the heat resistant polymer and the inorganic metal compound are used together, the average thickness of the heat resistant polymer and the inorganic metal compound layer may be about 0.002 to about 0.5 μm.

Another aspect of the invention provides a lithium ion secondary battery comprising the positive electrode for the lithium ion secondary battery.

Even when charging and discharging under high voltage and high temperature, the lithium manganese-based compound can be maintained in a stable state, and a positive electrode for a lithium ion secondary battery capable of suppressing deterioration of the positive electrode and expressing excellent cycle characteristics can be provided.

In addition, elution of manganese can be suppressed, and deterioration of not only the positive electrode but also the separator and the negative electrode can be suppressed.

It demonstrates in detail below.

A positive electrode for a lithium ion secondary battery according to an embodiment of the present invention includes a lithium manganese compound core and a heat resistant polymer positioned on the lithium manganese compound core, and the heat resistant polymer has a glass transition temperature (Tg) of about 80 to about 80 ° C. It is about 400 ° C.

The lithium manganese compound is a lithium intercalation compound in which the structural stability and capacity of the active material are determined by a reversible intercalation / deintercalation reaction of lithium ions. The lithium manganese compound may be selected from, for example, a compound represented by Formula 1 to Formula 4 or a combination thereof.

[Formula 1]

Li _x Mn _{1 - y} M _y A ₂

[Formula 2]

Li _x Mn _{1 - y} M _y O _{2 - z} X _z

(3)

Li _x Mn ₂ O _4-z X _z

[Formula 4]

Li _x Mn _{2 - y} M ' _y A ₄

Wherein 0.95≤x≤1.1, 0≤y≤0.7, 0≤z≤0.5, 0≤α≤2, M 'is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V and rare earth At least one element selected from the group consisting of elements, A is at least one element selected from the group consisting of O, F, S and P, and X is at least one element selected from the group consisting of F, S and P Element.

As the lithium manganese compound is used alone, as the charge and discharge proceeds, manganese is eluted with the electrolyte, and the eluted manganese component is deposited on the surface of the negative electrode active material, such as a carbon material, and receives electrons from the negative electrode active material. There is a problem that deterioration of the battery occurs by promoting decomposition of the active material to increase the resistance of the battery. Therefore, it can be seen that manganese deposited on the surface of the negative electrode active material rapidly decreases the reversible capacity in the lithium ion battery. Precipitation of such manganese components is more severe when stored at high temperature.

However, when the heat-resistant polymer is placed on the lithium manganese compound core according to one embodiment of the present invention, not only the lithium manganese compound present on the surface of the positive electrode plate but also the lithium manganese compound present inside the positive electrode plate are not dissolved. It can be suppressed. As a result, the decomposition reaction of the electrolyte solution is alleviated, so that elution of manganese, deterioration associated with precipitation, gas generation, and the like are suppressed, and excellent cycle characteristics can be expressed even when charging and discharging under high voltage and high temperature.

A heat resistant polymer having a glass transition temperature of about 80 ° C. to about 400 ° C. is positioned on the core particles of the lithium manganese compound. The heat resistant polymer may be a heat resistant polymer having a glass transition temperature of about 80 to about 400 ° C., for example, a polyamide (PA) resin, a polyimide (PI) resin, a polyamideimide (PAI) resin, or a polyacrylonitrile (PAN). ), Polysulfone (PS) resins, polybenzoimidazole (PBI) resins, polytetrafluoroethylene (PTFE) resins or copolymers thereof. More specifically, the glass transition temperature of the heat resistant polymer is, for example, the glass transition temperature of the polyacrylonitrile (PAN) resin is about 87 ℃, the glass transition temperature of the polyamideimide (PAI) resin is about 293 ℃, the glass transition temperature of the polysulfone (PS) resin is about 185 ℃, the glass transition temperature of the polybenzoimidazole (PBI) resin is about 270 ℃.

The polyamide resin may be a wholly aromatic polyamide-based resin. Examples of the wholly aromatic polyamide-based resin include, but are not limited to, poly (phenylene terephthalamide), poly (benzamide), poly (4,4'-benzanilidedoterphthalamide), poly (phenylene-4,4 ' Biphenylene dicarboxylic acid amide), poly (phenylene-2,6-naphthalenedicarboxylic acid amide), poly (2-chloro-phenylene terephthalamide), phenylene terephthalamide / 2,6-chlorophenylene The wholly aromatic polyamide-type resin (henceforth aramid resin), such as a terephthalamide polypolymer, is mentioned.

Melting | fusing point of the said aramid resin is about 180 degreeC or more, and is excellent in heat resistance. The optical properties of the aramid resin may be meta or para, and may be used alone or in combination of two or more.

By placing the heat resistant polymer on the lithium manganese compound core, for example, in the case of a lithium manganese compound, the elution of manganese is suppressed and the deterioration of the positive electrode is suppressed, and the separator and the negative electrode deteriorated caused by the eluted manganese simultaneously. Is also alleviated. For this reason, the cycling characteristics of a lithium ion secondary battery can be improved under high voltage and high temperature.

The method of placing the heat resistant polymer having the glass transition temperature of about 80 to about 400 ° C. on the lithium manganese compound core is not particularly limited. For example, a mechanical alloy that mechanically pulverizes and binds the lithium manganese compound core and the heat resistant polymer, a dry method in which the lithium manganese compound core and the heat resistant polymer or the inorganic metal compound are mixed and heated, and the lithium The wet method of immersing a manganese compound core in the coating liquid containing the said heat resistant polymer or the said inorganic metal compound may be sufficient.

The heat resistant polymer resin is used in about 0.01 parts by weight to about 3 parts by weight based on 100 parts by weight of the lithium manganese compound. Within this range, the heat resistance is improved and the inorganic metal compound may be uniformly coated on the surface of the active material.

The heat resistant polymer layer located on the lithium manganese based compound core has a thickness of about 0.002 to about 0.5 μm. When the thickness of the heat resistant polymer layer is within the above range, there is a continuous coating effect when coating the heat resistant polymer layer on the core of the lithium manganese-based compound, it is preferable that the heat resistance characteristics are evenly distributed.

According to one embodiment of the present invention, the inorganic metal compound as well as the heat resistant polymer having the glass transition temperature of about 80 to about 400 ° C. may be placed on the core particles of the lithium manganese compound.

Since the description of the lithium manganese-based compound and the heat-resistant polymer having the glass transition temperature of about 80 to about 400 ° C. is the same as described above, redundant descriptions are omitted.

Examples of the inorganic metal compound include at least one compound selected from the group consisting of oxides, hydroxides, nitrides, halides and sulfides; Or compounds containing at least one metal element selected from the group consisting of Al, Ti, Zr, Mg, Si, Li, Zn, La, Nb, Ta, Ge, Y, Se, B, or a combination thereof. have. Since the said inorganic metal compound is excellent in heat resistance and can expect the effect which improves electrolyte impregnation, when using the said inorganic metal compound together, it is good that the heat resistance and an ion conduction effect can be improved simultaneously.

The inorganic metal compound may, for _{example, Li 2 +2 x Zn 1 -x} GeO 4 ( where 0 <x <1), Li 4 -3x Ga x GeO 4 ( where 0 <x <1), La 2/3 _{- x Li 3x TiO 3 (0} · .03≤x≤0.167), La 1 / 3x Li 3x TaO 3 (0.025≤x≤0.167), La 1 / 3x Li 3x NbO 3 (0≤x≤ _{0.06), La 1 .3 Li 1} .7 Al 0 .3 (PO 4) 3, LiAlTa (PO 4) 3, LiAl 0.4 Ge 1.6 (PO 4) 3, Li 1 .4 Ti 1 .6 Y 0 .4 _{(PO 4) 3, Li 2} O · SeO 2 · B 2 O 3, LiCl·Li 1 .4 M 2 (PO 4) 3 ( where M is Al, Ti, Ge or a mixture thereof), Li _x PO _y N _z (where x = 2.9, y = 3.3, z = 0.46), Li _x BO _y N _z (where 0 <x <1, 0 <y <1, 0 <z <1), Li ₂ S · P ₂ O ₅ , Li ₂ S.SiS ₂ , Li ₂ S.SiS ₂ .Li _x MO ₄ (where M is Si, P, Ge or mixtures thereof, 0 <x <1), Li ₂ S.SiS ₂ .Li _{3 PO 4, Li 2 S ·} SiS 2 · xMS y ( wherein M is Sn, Ta, Ti or mixtures thereof, 0 <x <1), Li 2 S · SiS 2 · Li 3 N, Li 3 N · SiS ₂ , or a combination thereof.

The mixing ratio of the heat resistant polymer and the inorganic metal compound is preferably 5 to 50 parts by weight of the heat resistant polymer to 95 to 50 parts by weight of the inorganic metal compound, and more preferably 10 to 30 parts by weight of the heat resistant polymer to the inorganic metal compound 90 To 70 parts by weight, more preferably 15 to 25 parts by weight of the heat resistant polymer to 85 to 75 parts by weight of the inorganic metal compound. In particular, when the inorganic metal compound is included in the above range, the area of the coating layer located on the core of the lithium manganese compound can be prevented from becoming too dense, and the effect of improving the performance of the lithium ion secondary battery is considered to be further improved. In addition, the electrolyte impregnation effect can be improved as well as advantageous in terms of ion conductivity effect and heat resistance effect.

The method of using together and positioning the said heat resistant polymer and the said inorganic metal compound on the said lithium manganese type compound core is not specifically limited. For example, a mechanical alloy which mechanically pulverizes and binds the lithium manganese compound core and the heat resistant polymer or the inorganic metal compound, and heats after mixing the lithium manganese compound core and the heat resistant polymer or the inorganic metal compound Any of the dry method and the wet method in which the lithium manganese compound core is immersed in the coating liquid containing the heat resistant polymer or the inorganic metal compound may be used. After the production of the positive electrode plate from the positive electrode active material particles, the positive electrode plate may be dipped in a coating solution containing a polyamide resin or an inorganic metal compound to coat the positive electrode active material particles contained in the positive electrode plate.

In addition, the heat resistant polymer and the inorganic metal compound composite layer positioned on the lithium manganese compound core also have a thickness of about 0.002 to about 0.5 μm. Within the above range, there is a continuous coating effect as described above, it is good that the heat resistance characteristics are evenly distributed.

When placed in combination with a heat-resistant polymer and an inorganic metal compound having a glass transition temperature of about 80 to about 400 ° C. on the lithium manganese compound core, when the layer located on the core becomes too thick, the reaction between the anode and the electrolyte is inhibited. Resulting in a decrease in capacity. For this reason, the average thickness of the layer located on the core is preferably about 0.002 µm to about 0.5 µm or less, more preferably about 0.002 µm to about 0.2 µm or less. The thickness can be measured by transmission electron micryscopy (TEM). That is, by taking a TEM photograph, the lithium manganese-based active material core and the heat resistant polymer or the shell portion of the heat resistant polymer and the inorganic metal compound can be distinguished from each other. For example, measure 10 times and calculate the average value.

In addition, a layer including a heat resistant polymer having a glass transition temperature of about 80 ° C. to about 400 ° C. may be formed on the cathode plate made of the cathode active material, and a layer including an inorganic metal compound may be disposed together with the heat resistant polymer.

One embodiment of the present invention provides a lithium ion secondary battery including the positive electrode for a lithium ion secondary battery. Hereinafter, a lithium ion secondary battery according to an embodiment of the present invention will be described.

Examples of the lithium ion secondary battery according to the present embodiment may have a coin type, a button type, a sheet type, a cylinder type, a flat type, a square type, and the like, and the lithium ion secondary battery may be a positive electrode, a negative electrode, an electrolyte, or a separator. And the like.

Since the positive electrode for a lithium ion secondary battery is as described above, the same description is omitted.

Examples of the negative electrode include graphite-based carbon materials, silicon, tin, silicon alloys, tin alloys, silicon oxides, lithium vanadium oxide, and the like as active materials, and in particular, silicon, tin, silicon alloys, tin alloys, and the like. It is preferable to use a compound alloyable with lithium, or silicon oxide, lithium vanadium oxide, or the like as the active material.

The capacity density of silicon, tin, silicon alloy, tin alloy, silicon oxide, lithium vanadium oxide, etc. is about 850 mAh / cm ³ or more, while the capacity density of graphite-based carbon material is about 560 to about 630 mAh / cm ³ . By using these, the battery can be miniaturized and high in capacity. On the other hand, these negative electrode active materials may be used alone or in combination of two or more thereof.

The positive electrode and the negative electrode may be appropriately selected and blended with the powder of the above-mentioned active material, for example, an additive such as an electrically conductive material, a binder, a filler, a dispersant, and an ion electrically conductive material.

Examples of the electrically conductive material include graphite, carbon black, acetylene black, KETJEN BLACK, carbon fiber, and metal powder. Examples of the binder include polytetrafluoroethylene and polyvinylidene fluoride (PVdF). And polyethylene.

In the production of the positive electrode or the negative electrode, for example, a mixture of an electrically active substance and various additives is added to a solvent such as water or an organic solvent to form a slurry or paste, and the obtained slurry or paste is obtained by a doctor blade method. It can apply | coat to an electrode support board | substrate using etc., dry, and it can manufacture by crimping | compressing / compressing with a rolling roll etc.

Examples of the electrode support substrate may include a foil, a sheet or net made of copper, nickel, stainless steel, or the like, and a sheet or net made of carbon fiber. On the other hand, a cathode can be manufactured by crimping / compressing and forming a pallet type, without using an electrode support substrate.

Examples of the electrolyte include a nonaqueous electrolyte in which lithium salt is dissolved in an organic solvent, a polymer electrolyte, an inorganic solid electrolyte, a composite material of a polymer electrolyte and an inorganic solid electrolyte, and the like.

Examples of the solvent of the nonaqueous electrolytic solution include chain carbonates such as cyclic carbonates such as ethylene carbonate, propylene carbonate and vinylene carbonate, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate; γ-lactones such as γ-butyl lactone: chain ethers such as 1,2-dimethoxyethane, 1,2-diethoxyethane and ethoxymethoxyethane: cyclic ethers of tetrahydrofuran: acetonitrile and the like Nitriles, and the like. These solvents may be used alone or in combination of two or more thereof.

Examples of the lithium salt that is the solute of the nonaqueous electrolyte include LiAsF ₆ , LiBF ₄ , LiPF ₆ , LiAlCl ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiSbF ₆ , LiSCN, LiCl, LiC ₆ H ₅ SO ₃ , LiN ( CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC ₄ P ₉ SO ₃ , and the like.

Examples of the separator include a porous membrane made of polyolefin such as polypropylene or polyethylene. Furthermore, a polyamide layer may be provided on the porous membrane, and this may be a polyamide layer containing an inorganic metal compound.

Hereinafter, examples and comparative examples of the present invention are described. The following examples are described in more detail as one preferred embodiment of the present invention, but the present invention is not limited to the following examples.

(Example 1)

About 94.75% by weight of LiMn ₂ O ₄ having a particle size of about 10 μm was added to a solution in which 0.25% by weight of polyimide (PI) resin was dissolved in N-methyl-2-pyrrolidone (NMP) and stirred with a stirring apparatus. Thereafter, the solution and the solid were separated by filtration, and the solid was vacuum dried at 160 ° C. The thickness of the layer located on the LiMn ₂ O ₄ core was about 0.005 μm. The solid was mixed with acetylene black and polyvinylidene fluoride (PVdF) at 94: 3: 3 to obtain a positive electrode active material slurry, and the slurry was coated on an aluminum substrate to prepare a positive electrode.

N-methyl-2-pyrrolidone was added to about 3% by weight of graphite powder and 3% by weight of polyvinylidene fluoride (PVdF) as a binder to form a negative electrode active material slurry, which was then coated on a copper foil which is a negative electrode current collector. Was prepared.

A polypropylene separator was interposed between the prepared positive and negative electrodes, and a nonaqueous electrolyte was injected to prepare a coin-type lithium ion secondary battery. The nonaqueous electrolyte was prepared using a nonaqueous electrolyte in which LiPF ₆ was dissolved at a concentration of 1.50 mol / L in a mixed solvent prepared by mixing ethylene carbonate and diethyl carbonate in a ratio of 3: 7.

(Example 2)

A positive electrode was prepared in the same manner as in Example 1 by mixing and coating a heat-resistant polymer PI and an inorganic metal compound LiAlTa (PO ₄ ) ₃ in a weight ratio of 1: 3 on the LiMn ₂ O ₄ particle surface, and including the obtained positive electrode. A lithium secondary battery was manufactured in the same manner as in Example 1.

(Example 3)

_{LiNi 0 .5 Co 0 .2 Mn 0} .3 O 2 particles to prepare a positive electrode in the same manner as in Example 1 by coating a heat-resistant polymer PI on the surface and in the same manner as in Example 1 with lithium include the above-obtained positive electrode A secondary battery was prepared.

(Example 4)

_{LiNi 0 .5 Co 0 .2 Mn 0} .3 O 2 particle surface a heat-resistant polymer and the inorganic metal compound to the PI LiAlTa (PO _{4) 3} weight ratio of 1: Preparation Example 1, a positive electrode was coated in the same manner and then mixed with 3 And, a lithium secondary battery was prepared in the same manner as in Example 1 including the obtained positive electrode.

(Comparative Example 1)

LiMn ₂ O ₄ , carbon-based conductive material acetylene black, and PVdF binder were mixed at 94: 3: 3 to prepare a positive electrode slurry and coated on an aluminum substrate to prepare a positive electrode, the same as in Example 1 including the positive electrode. A lithium ion secondary battery was prepared.

(Comparative Example 2)

_{LiNi 0 .5 Co 0 .2 Mn 0} .3 to O ₂ and the carbon-based conductive material of acetylene black and PVdF binder 94: 3: 3 to produce a mixture with the positive electrode slurry to produce a positive electrode was coated on an aluminum substrate, wherein A lithium ion secondary battery was manufactured in the same manner as in Example 1 including a positive electrode.

(Battery performance evaluation)

Charge and discharge experiments of the coin-type lithium secondary batteries prepared according to Examples 1 to 4 and Comparative Examples 1 to 2 were performed. First, a charge and discharge experiment was performed with a charge and discharge current density of 0.1C, a charge end voltage of 4.3V (Li / Li +), and a discharge end voltage of 3.0V (Li / Li +).

Subsequently, the charge and discharge current densities were 0.2C and 0.5C, and each current density was performed once each under the above charge and discharge termination voltage conditions, and then, 50 times were performed under the current density conditions of 1.0C. The charge and discharge experiments were all made in a 60 ℃ high temperature chamber.

All charging and discharging were performed by constant current. After completion of a total of 50 cycles of tests, the discharge capacity (initial capacity) and charge / discharge efficiency (discharge capacity / charge capacity, initial efficiency) of the first cycle were determined. Then, the capacity ratio (50th / 1st), which is divided by the discharge capacity of 50 cycles by the discharge capacity of the first cycle of 0.1C, was obtained to obtain a capacity retention rate. Evaluation was made as an average value after producing and evaluating three or more coin-type lithium secondary batteries about the same binder composition. The results are shown in Table 1 below.

TABLE 1

Initial capacity (mAh / g) Initial discharge efficiency (%) 50 cycles capacity retention rate (%) Example 1 115.9 80.6 82.6 Example 2 117.2 80.5 88.1 Comparative Example 1 121.9 71.8 54.5 Example 3 158.2 88.6 89.4 Example 4 156.2 88.2 92.1 Comparative Example 2 160.4 87.5 80.9

As can be seen in Table 1, the lithium manganese oxide particles are coated by using a heat-resistant polymer having a glass transition temperature (Tg) of 80 to 400 ° C. or an inorganic metal compound together with the heat-resistant polymer according to Examples 1 to 4. The lithium ion secondary battery prepared by comparing the lithium ion secondary battery prepared according to Comparative Examples 1 to 2 it can be confirmed that the excellent performance of the battery.

More specifically, when comparing Examples 1, 2 and Comparative Example 1 using LiMn ₂ O ₄ as a lithium manganese compound core, LiMn ₂ O ₄ particles compared to Comparative Example 1 using LiMn ₂ O ₄ alone It can be seen that the capacity retention rate of the battery of Example 1 in which the heat-resistant polymer is coated on the surface and the heat-resistant polymer and the inorganic metal compound are coated on the surface of the LiMn ₂ O ₄ particles is about 30%.

Further, as a lithium manganese-based compound core _{LiNi 0 .5 Co 0 .2 Mn 0} .3 O performed using ₂ A comparison of the Examples 3 and 4 and Comparative Example 2, _{LiNi 0 .5 Co 0 .2 Mn 0} .3 O compared to Comparative example 2 using _{2 alone, LiNi 0 .5 Co 0 .2 Mn} 0 .3 O 2 coated with the heat-resistant polymer particles carried on the surface example 3 and LiNi _0.5 Co _0.2 Mn _0.3 O ₂ heat-resistant polymer to the particle surface And it can be seen that the capacity retention rate of the battery of Example 4 coated with an inorganic metal compound is about 10% advantageous.

Therefore, when manufacturing a lithium secondary battery using a positive electrode active material having a heat-resistant polymer or a heat-resistant polymer and an inorganic metal compound on the core of the lithium manganese-based compound, due to the effect of suppressing elution of manganese from the lithium manganese-based compound It can be seen through the above examples and comparative examples that the performance of the battery is improved.

Claims (15)

Lithium manganese compound core and It comprises a heat-resistant polymer located on the lithium manganese compound core, The heat resistant polymer has a glass transition temperature (Tg) of 80 to 400 ℃ positive electrode for a lithium ion secondary battery. The method of claim 1, The heat resistant polymer is polyamide (PA) resin, polyimide (PI) resin, polyamideimide (PAI) resin, polyacrylonitrile (PAN) resin, polysulfone (PS) resin, polybenzoimidazole (PBI) resin , Polytetrafluoroethylene (PTFE) resin, or a copolymer thereof, and a combination thereof, the positive electrode for a lithium ion secondary battery. The method of claim 1, The polyamide resin is a cathode for a lithium ion secondary battery that is a wholly aromatic polyamide-based resin. The method of claim 1, The amount of the heat resistant polymer resin is in the range of 0.01 parts by weight to 3 parts by weight based on 100 parts by weight of the lithium manganese-based compound positive electrode for a lithium ion secondary battery. The method of claim 1, An average thickness of the heat resistant polymer layer is 0.002㎛ 0.5㎛ positive electrode for secondary batteries. Lithium manganese compound core and Comprising a heat-resistant polymer and an inorganic metal compound located on the manganese-based compound core, wherein the heat-resistant polymer is a glass transition temperature of 80 to 400 ℃ positive electrode for a lithium ion secondary battery. The method of claim 5, The heat resistant polymer is polyamide (PA) resin, polyimide (PI) resin, polyamideimide (PAI) resin, polyacrylonitrile (PAN) resin, polysulfone (PS) resin, polybenzoimidazole (PBI) resin , Polytetrafluoroethylene (PTFE) resin, or a copolymer thereof, and a combination thereof, the positive electrode for a lithium ion secondary battery. The method of claim 5, The polyamide resin is a wholly aromatic polyamide-based resin positive electrode for a lithium ion secondary battery. The method of claim 5, The amount of the heat resistant polymer resin is in the range of 0.01 parts by weight to 3 parts by weight based on 100 parts by weight of the lithium manganese-based compound positive electrode for a lithium ion secondary battery. The method of claim 5, The inorganic metal compound is selected from the group consisting of oxides, hydroxides, nitrides, halides, sulfides and combinations thereof. The method of claim 5, The metal of the inorganic metal compound is selected from Al, Ti, Zr, Mg, Si, Li, Zn, La, Nb, Ta, Ge, Y, Se, B or a combination thereof. The method of claim 5, The inorganic metal compound is Li _{2 + 2x} Zn _1-x GeO ₄ (where 0 <x <1), Li _4-3x Ga _x GeO ₄ (here 0 <x <1), La _{2 / 3-x} Li _3x TiO ₃ (0..03≤x≤0.167), La _{1 / 3-x} Li _3x TaO ₃ (0.025≤x≤0.167), La _{1 / 3-x} Li _3x NbO ₃ (0≤x≤0.06), La _1.3 Li _1.7 Al _0.3 (PO ₄ ) ₃ , LiAlTa (PO ₄ ) ₃ , LiAl _0.4 Ge _1.6 (PO ₄ ) ₃ , Li _1.4 Ti _1.6 Y _0.4 (PO ₄ ) ₃ , Li ₂ OSeO ₂ B ₂ O ₃ , LiCl-Li _1.4 M ₂ (PO ₄ ) ₃ , where M is Al, Ti, Ge or mixtures thereof, Li _x PO _y N _z (where x = 2.9, y = 3.3, z = 0.46), Li _x BO _y N _z (where 0 <x <1, 0 < y <1, 0 <z <1), Li 2 S · P 2 O 5, Li 2 S · SiS 2, Li 2 S · SiS 2 · Li _x MO ₄ (wherein M is Si, P, Ge or a mixture thereof, 0 <x <1), Li 2 S · SiS 2 · Li 3 PO 4, Li 2 S · SiS 2 · xMS y ( wherein M is Sn , Ta, Ti or a mixture thereof, 0 <x <1), Li ₂ S.SiS ₂ .Li ₃ N, Li ₃ N.SiS ₂ , or a combination thereof. The method of claim 5, The mixing ratio of the heat-resistant snow polymer and the inorganic metal compound is 5 to 50 parts by weight of the heat resistant polymer to 95 to 50 parts by weight of the inorganic metal compound. The method of claim 5, The average thickness of the heat resistant polymer and the inorganic metal compound layer is 0.002㎛ 0.5㎛ positive electrode for a secondary battery. The lithium ion secondary battery containing the positive electrode for lithium ion secondary batteries of any one of Claims 1-14.