WO2018124593A1 - Cathode active material for secondary battery, method for manufacturing same, and lithium secondary battery comprising same - Google Patents

Abstract

The present invention relates to a cathode active material for a secondary battery, comprising: a lithium transition metal oxide containing nickel (Ni), cobalt (Co), and at least one selected from the group consisting of manganese (Mn) and aluminum (Al), wherein the content of nickel (Ni) in the total transition metal element in the lithium transition metal oxide is 80 mol% or more, and the cation mixing ratio of Ni cations in a lithium layer in the lithium transition metal oxide structure is 1.1% or less.

Description

Cathode active material for secondary battery, manufacturing method thereof and lithium secondary battery comprising same

Citation with Related Applications

This application claims the benefit of priority based on Korean Patent Application No. 10-2016-0181022 dated December 28, 2016 and Korean Patent Application No. 10-2017-0174131 dated December 18, 2017. All content disclosed in the literature is included as part of this specification.

Field of technology

The present invention relates to a cathode active material for a secondary battery, a manufacturing method thereof, and a lithium secondary battery including the same.

As technology development and demand for mobile devices increase, the demand for secondary batteries as a source of energy is rapidly increasing. Among such secondary batteries, lithium secondary batteries having high energy density and voltage, long cycle life, and low self discharge rate have been commercialized and widely used.

Lithium transition metal composite oxide is used as a positive electrode active material of a lithium secondary battery, and among these, lithium cobalt composite metal oxide of LiCoO ₂ having a high operating voltage and excellent capacity characteristics is mainly used. However, since LiCoO ₂ is very poor in thermal properties due to destabilization of crystal structure due to de-lithium and is expensive, there is a limit to using LiCoO ₂ as a power source in fields such as electric vehicles.

As a material for replacing LiCoO ₂ , lithium manganese composite metal oxides (such as LiMnO ₂ or LiMn ₂ O ₄ ), lithium iron phosphate compounds (such as LiFePO ₄ ), or lithium nickel composite metal oxides (such as LiNiO ₂ ) have been developed. Among them, research and development of lithium nickel composite metal oxides having a high reversible capacity of about 200 mAh / g, which is easy to implement a large-capacity battery, have been actively studied. However, LiNiO ₂ has a poor thermal stability compared to LiCoO _2, and when an internal short circuit occurs due to pressure from the outside in a charged state, the positive electrode active material itself decomposes, causing a battery to rupture and ignite.

Accordingly, as a method for improving low thermal stability while maintaining excellent reversible capacity of LiNiO ₂ , nickel cobalt manganese-based lithium composite metal oxide in which a part of Ni is substituted with Mn and Co (hereinafter, simply referred to as 'NCM-based lithium oxide'). Has been developed. However, the conventional NCM-based lithium oxide developed to date has a limitation in application due to insufficient capacity characteristics.

In order to improve such a problem, researches have recently been made to increase the content of Ni in NCM-based lithium oxide. However, in the case of a high nickel content of a high concentration of the nickel positive electrode active material, there is a problem that the structural stability and chemical stability of the active material is lowered, the thermal stability is sharply lowered. In addition, as the nickel content in the active material increases, the amount of lithium by-products present in the form of LiOH and Li ₂ CO ₃ on the surface of the positive electrode active material increases, resulting in gas generation and swelling, thereby improving battery life and stability. The problem of deterioration also arises.

Accordingly, there is a demand for development of a high-density nickel (Ni-rich) cathode active material having high residual capacity and low residual amount of lithium by-products while meeting high capacity.

The present invention is to solve the above problems, high concentration nickel positive electrode active material that can simultaneously realize structural stability, excellent capacity characteristics and high temperature stability with a small amount of lithium by-products, a method of manufacturing the same, and a secondary battery positive electrode comprising the same And to provide a lithium secondary battery.

The present invention comprises the steps of preparing a lithium transition metal oxide containing nickel (Ni), cobalt (Co), at least one selected from the group consisting of manganese (Mn) and aluminum (Al); Washing the lithium transition metal oxide to remove lithium impurities present on the surface of the lithium transition metal oxide; And a high temperature heat treatment of the lithium transition metal oxide after washing with water, wherein the high temperature heat treatment includes: an elevated temperature section for heating and heating the temperature, a holding section for maintaining the elevated temperature, and cooling the temperature; It includes a section, the temperature rising section provides a method for producing a positive electrode active material for secondary batteries 20 to 30% of the total high temperature heat treatment time.

In addition, the present invention includes a lithium transition metal oxide containing nickel (Ni), cobalt (Co), at least one selected from the group consisting of manganese (Mn) and aluminum (Al), the lithium transition metal The oxide is a positive electrode active material for secondary batteries having a nickel (Ni) content of at least 80 mol% of all transition metal elements, and a cation mixing ratio of Ni cations in the lithium layer in the lithium transition metal oxide structure is 1.1% or less. to provide.

In addition, the present invention provides a cathode and a lithium secondary battery including the cathode active material.

According to the present invention, by performing a high temperature heat treatment under specific conditions after washing with water, while the residual amount of lithium by-products is reduced, structural stability is improved while recrystallization of the crystalline structure in which lithium escapes and is destroyed in the crystal structure, resulting in excellent high temperature stability. A positive electrode active material can be manufactured. In addition, unlike the conventional high-concentration nickel positive electrode active material, not only is structurally stable, but also may exhibit a secondary battery having excellent capacity characteristics and small resistance increase rate even when repeated charging.

1 is a graph showing heat flow with respect to the temperature of a cathode active material according to Examples and Comparative Examples.

2 is a graph showing capacity retention rates for charge and discharge cycles of battery cells manufactured using positive electrode active materials according to Examples and Comparative Examples.

3 is a graph illustrating a resistance increase rate with respect to a charge / discharge cycle of a battery cell manufactured using a cathode active material according to Examples and Comparative Examples.

Hereinafter, the present invention will be described in more detail to aid in understanding the present invention. At this time, the terms or words used in the present specification and claims should not be construed as being limited to the ordinary or dictionary meanings, and the inventors appropriately define the concept of terms in order to explain their invention in the best way. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that it can.

The present invention reduces the residual amount of lithium by-products by washing the lithium transition metal oxide containing high concentration of nickel with high temperature and washing it at a specific condition, thereby reducing the residual amount of lithium by-products and recrystallization of the crystal structure in which lithium is released and destroyed. This improved high concentration nickel-based cathode active material can be prepared.

Specifically, the present invention comprises the steps of preparing a lithium transition metal oxide containing nickel (Ni), cobalt (Co), and at least one selected from the group consisting of manganese (Mn) and aluminum (Al); Washing the lithium transition metal oxide to remove lithium impurities present on the surface of the lithium transition metal oxide; And a high temperature heat treatment of the lithium transition metal oxide after washing with water, wherein the high temperature heat treatment includes: an elevated temperature section for heating and heating the temperature, a holding section for maintaining the elevated temperature, and cooling the temperature; It includes a section, the temperature rising section provides a method for producing a positive electrode active material for secondary batteries 20 to 30% of the total high temperature heat treatment time.

First, a lithium transition metal oxide including nickel (Ni) and cobalt (Co) and including at least one selected from the group consisting of manganese (Mn) and aluminum (Al) is prepared.

Specifically, the lithium transition metal oxide may be represented by the following formula (1).

[Formula 1]

Li _a Ni _1-x1-y1-z1 Co _x1 M ¹ _y1 M ² _z1 M ³ _q1 O ₂

In Formula 1, M ¹ is at least one selected from the group consisting of Mn and Al, M ² and M ³ are each independently Ba, Ca, Zr, Ti, Mg, Ta, Nb, W and Mo At least one selected from the group consisting of: 1.0 ≦ a ≦ 1.5, 0 <x1 ≦ 0.2, 0 <y1 ≦ 0.2, 0 ≦ z1 ≦ 0.1, 0 ≦ q1 ≦ 0.1, 0 <x1 + y1 + z1 ≦ 0.2 to be.

In the lithium transition metal oxide of Chemical Formula 1, Li may be included in an amount corresponding to a, that is, 1.0 ≦ a ≦ 1.5. If a is less than 1.0, the capacity may be lowered. If a is more than 1.5, the particles may be sintered in the firing process, and the production of the positive electrode active material may be difficult. Considering the remarkable effect of improving the capacity characteristics of the positive electrode active material according to the control of the Li content and the balance of the sintering property during manufacturing of the active material, the Li may be more preferably included in a content of 1.0≤a≤1.15.

In addition, in the lithium transition metal oxide of Chemical Formula 1, Ni may be included in an amount corresponding to 1-x1-y1-z1, that is, 0.8≤1-x1-y1-z1 <1. More preferably Ni may be included as 0.8≤1-x1-y1-z1 <0.9. When the Ni content in the lithium transition metal oxide of Formula 1 is 0.8 or more, the amount of Ni sufficient to contribute to charging and discharging may be secured, thereby achieving high capacity. If the content of Ni is less than 0.8, there may be a limit to the implementation of high capacity.In the composition of more than 0.9, part of the Li site may be replaced by Ni to obtain sufficient amount of Li to contribute to charge and discharge. There is a risk of deterioration.

In addition, in the lithium transition metal oxide of Chemical Formula 1, Co may be included in an amount corresponding to x1, that is, 0 <x1 ≦ 0.2. When the content of Co in the lithium transition metal oxide of Formula 1 exceeds 0.2, efficiency of capacity improvement may be deteriorated compared to an increase in cost. Considering the remarkable effect of improving the capacity characteristics according to the inclusion of Co, Co may be included in a content of 0.05≤x≤0.2 more specifically.

In addition, in the lithium transition metal oxide of Chemical Formula 1, M ¹ may be Mn or Al, or Mn and Al, and these metal elements may improve the stability of the active material and, as a result, improve the stability of the battery. In consideration of the improvement of lifespan characteristics, M ¹ may be included in an amount corresponding to y1, that is, 0 <y1 ≦ 0.2. When y1 in the lithium composite transition metal oxide of Formula 1 exceeds 0.2, there is a concern that the output characteristics and capacity characteristics of the battery may be lowered, and M ¹ may be included in an amount of 0.05 ≦ y1 ≦ 0.2.

In addition, in the lithium transition metal oxide of Chemical Formula 1, M ² may be a doping element included in the crystal structure of the lithium composite transition metal oxide, and M ² may be included in an amount corresponding to z 1, that is, 0 ≦ z ¹ ≦ 0.1. have.

In addition, in the lithium transition metal oxide of Formula 1, the metal element of M ³ may not be included in the lithium composite transition metal oxide structure, and when the precursor and the lithium source are mixed and calcined, the M ³ source may be mixed together and calcined. After forming a lithium composite transition metal oxide, a lithium composite transition metal oxide doped on the surface of the M ³ lithium composite transition metal oxide may be prepared by separately adding an M ³ source and firing. The M ³ may be included in an amount corresponding to q1, that is, in an amount of 0 ≦ q1 ≦ 0.1, so as not to degrade the characteristics of the positive electrode active material.

The lithium transition metal oxide used in the present invention may be an NCM-based lithium composite transition metal oxide including nickel (Ni), cobalt (Co) and manganese (Mn), or nickel (Ni), cobalt (Co) and It may be an NCA-based lithium composite transition metal oxide including aluminum (Al). In addition, the positive electrode active material may be a four-component lithium composite transition metal oxide including essentially four components of nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al).

In addition, the lithium transition metal oxide used in the present invention may be a high-nickel-based lithium transition metal oxide having a molar ratio of nickel of 0.8 or more in the total molar ratio of the transition metal in the lithium transition metal oxide.

The lithium transition metal oxide of Chemical Formula 1 is not limited thereto, but may be, for example, a mixture of a precursor represented by Chemical Formula 2 and a lithium-containing raw material, and then fired at 700 to 900 ° C. . More preferably, it can bake in oxygen atmosphere at the said baking temperature.

[Formula 2]

Ni _1-x2-y2-z2 Co _x2 M ¹ _y2 M ² _z2 (OH) ₂

In Formula 2, M ¹ is at least one selected from the group consisting of Mn and Al, M ² is at least selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb, W and Mo 1 or more types, 0 <x2 <= 0.2, 0 <= y2 <0.2, 0 <z2 <0.1, and 0 <x2 + y2 + z2 <0.2.

In the cathode active material precursor of Formula 2, the preferred composition of Ni, Co, M ¹ and M ² may be the same as the range of the composition of the lithium transition metal oxide described above.

The lithium-containing raw material material may be lithium-containing carbonate (e.g., lithium carbonate), hydrate (e.g., lithium hydroxide I hydrate (LiOH, H ₂ O), etc.), hydroxide (e.g., lithium hydroxide, etc.), nitrate (Eg, lithium nitrate (LiNO ₃ ), etc.), chlorides (eg, lithium chloride (LiCl), and the like), and the like, and one of these may be used alone or a mixture of two or more thereof may be used. Lithium carbonate may be used.

Next, the lithium transition metal oxide prepared as described above is washed with water to remove lithium by-products remaining in the lithium transition metal oxide.

In the case of the lithium transition metal oxide containing a high concentration of nickel, such as the lithium transition metal oxide of the present invention, because the structural unstable compared to the lithium transition metal oxide having a low nickel content and unreacted lithium hydroxide or lithium carbonate in the manufacturing process More lithium by-products are produced. Specifically, in the case of lithium composite metal oxide having a nickel content of less than 80 mol%, the amount of lithium by-products after synthesis is about 0.5 to 0.6 wt%, whereas in the case of a lithium composite metal oxide having a nickel content of 80 mol% or more, lithium after synthesis The amount of by-products appears as high as 1% by weight. On the other hand, when a large amount of lithium by-products are present in the positive electrode active material, lithium by-products and electrolytes react to generate gas and swelling, and thus high temperature stability is significantly lowered. Therefore, a washing process for removing lithium by-products from lithium transition metal oxides containing high concentrations of nickel is essential.

The washing step may be performed, for example, by adding a lithium transition metal oxide to pure water and stirring.

In this case, the washing with water may be performed using 50 to 100 parts by weight of pure water with respect to 100 parts by weight of lithium transition metal oxide.

If the amount of pure water is less than 50 parts by weight based on 100 parts by weight of the lithium transition metal oxide during washing, insufficient cleaning may be insufficient, and if the amount of pure water exceeds 100 parts by weight, lithium in the crystal structure may be insufficient. The amount of dissolved water may increase, particularly in the case of a lithium transition metal oxide having a high nickel content of at least 80 mol%, the amount of lithium dissolved in the crystal structure is significantly reduced when the pure water content is too large. Increasingly, a sudden decrease in the capacity and life of the battery may occur.

In addition, the washing temperature may be 30 ℃ or less, preferably -10 ℃ to 30 ℃, the washing time may be about 10 minutes to 1 hour. When the water washing temperature and the water washing time satisfy the above range, lithium by-products can be effectively removed.

Next, the washed lithium transition metal oxide is subjected to high temperature heat treatment.

At this time, the step of the high temperature heat treatment, the temperature increase and the heat treatment section for heat treatment includes a maintenance section for heat treatment while maintaining the elevated temperature and a cooling section for cooling the temperature. The temperature increase section is preferably 20 to 30% of the total high temperature heat treatment time.

The high temperature heat treatment step is to improve the structural stability and thermal stability by further removing lithium by-products, and recrystallization of the metal elements in the positive electrode active material through high temperature heat treatment. In the case of the lithium transition metal oxide containing high concentration of nickel, washing with water is performed to remove residual lithium by-products. When washing with lithium, not only lithium by-products but also lithium in the crystal structure are released and crystallinity is reduced and stability is lowered. Accordingly, the present invention is a high-temperature heat treatment of the washed transition metal oxide under the above conditions, thereby recrystallizing the metal elements of the lithium transition metal oxide to fill the vacancy of lithium, and improved surface stability.

If the elevated temperature range is less than 20% of the total high temperature heat treatment time, the remaining moisture may not be sufficiently removed after the washing process, and thus, battery performance may be deteriorated, such as a decrease in electrical conductivity. If the temperature exceeds 30%, the crystallization may not be effectively performed. The cation mixing ratio of the Ni cation may increase.

The holding section may be 40 to 50% of the total high temperature heat treatment time. The cooling section may be 20 to 30% of the total high temperature heat treatment time. By satisfying the ratio of the temperature rising section, the holding section and the cooling section within the above ranges, residual water may be removed, residual lithium by-products may be further removed, and recrystallization may be effectively improved to significantly improve stability.

The total time of the high temperature heat treatment is preferably within 10 hours, specifically, the total high temperature heat treatment time may be 6 hours to 10 hours.

The temperature increase rate of the temperature increase section may be 2 to 7 ℃ / min, more preferably 3 to 6 ℃ / min. The heat treatment temperature of the organic section may be 600 ° C or more, more preferably 600 to 900 ° C. The cooling section may be cooled in a natural cooling manner.

When the time and heat treatment temperature of each section of the high temperature heat treatment step satisfy the above range, the thermal stability improvement effect is excellent. According to the researches of the present inventors, it was found that there is little effect of improving the thermal stability when the heat treatment temperature of the holding section is less than 600 ℃.

On the other hand, the high temperature heat treatment may be performed in an oxygen atmosphere, specifically, an oxygen partial pressure of 80% or more, more preferably 80 to 99%, even more preferably 90 to 95%. When heat treatment is performed in an oxygen atmosphere as in the present invention, lithium by-products can be effectively removed and recrystallization can occur effectively. According to the researches of the present inventors, the effect of removing lithium by-products is remarkably decreased when the heat treatment is performed in the air. In particular, when the heat treatment is performed at 600 ° C. or higher, the amount of lithium by-products is increased rather than before heat treatment.

The high temperature heat-treated lithium transition metal oxide is H ₃ BO ₃ , B ₂ O ₃ And it may be mixed with at least one selected from the group consisting of Al ₂ O ₃ and heat treatment to form a coating layer on the surface of the lithium transition metal oxide. At this time, the heat treatment may be performed at a temperature of 200 to 500 ℃. By performing the coating heat treatment further, the crystallinity may be improved, and the stability of the cathode active material may be further improved.

Next, the positive electrode active material for secondary batteries according to the present invention will be described.

The cathode active material for a secondary battery of the present invention manufactured by the above method includes nickel (Ni) and cobalt (Co), and includes at least one or more selected from the group consisting of manganese (Mn) and aluminum (Al). The lithium transition metal oxide has a nickel (Ni) content of 80 mol% or more in all transition metal elements, and a cation mixing ratio of Ni cations in the lithium layer in the lithium transition metal oxide structure is 1.1% or less.

The lithium transition metal oxide may be represented by the following Chemical Formula 1.

[Formula 1]

Li _a Ni _1-x1-y1-z1 Co _x1 M ¹ _y1 M ² _z1 M ³ _q1 O ₂

In Formula 1, M ¹ is at least one selected from the group consisting of Mn and Al, M ² and M ³ are each independently Ba, Ca, Zr, Ti, Mg, Ta, Nb, W and Mo At least one selected from the group consisting of: 1.0 ≦ a ≦ 1.5, 0 <x1 ≦ 0.2, 0 <y1 ≦ 0.2, 0 ≦ z1 ≦ 0.1, 0 ≦ q1 ≦ 0.1, 0 <x1 + y1 + z1 ≦ 0.2 to be. Specific specifications of the lithium transition metal oxide represented by Chemical Formula 1 are the same as those described in the manufacturing method, and thus, detailed description thereof will be omitted.

In the case of a conventional lithium transition metal oxide containing high concentration of nickel, when washing with water to remove the residual lithium by-products, the lithium in the crystal structure as well as the lithium by-products during the washing together, the crystallinity is lowered, Ni cation The amount of cation mixing to be incorporated into this lithium layer has increased. This is indicated by the deterioration of the electrochemical properties.

Accordingly, the present invention, in order to produce a positive electrode active material having excellent electrochemical characteristics such as discharge capacity and lifespan, after washing the lithium transition metal oxide containing a high concentration of nickel, and then heat treatment under high temperature in an oxygen atmosphere of the lithium transition metal oxide The layered structure was well developed and the amount of cation mixing of Ni cations in the lithium layer was 1.1% or less. More preferably, the amount of cation mixing may be 1.0% or less. When the amount of cation mixing in which the Ni cation is incorporated in the lithium layer satisfies the above range, the capacity characteristics of the lithium transition metal oxide may be excellent, but the high temperature stability and the life characteristics may be effectively improved.

In addition, the cathode active material according to the present invention as described above is manufactured through a process of high temperature heat treatment in an oxygen atmosphere after washing with water, the residual amount of lithium by-products can be significantly reduced. Preferably the content of lithium by-product present in the positive electrode active material may be more than 0.3% to 1% by weight, more preferably more than 0.3% to 0.6% by weight, more preferably more than 0.35% to 0.5% by weight It may be less than or equal to%. As described above, the cathode active material according to the present invention satisfies the amount of residual lithium by-products within the above range, thereby effectively forming a coating layer by reaction between the lithium by-products and the coating source, thereby effectively suppressing gas generation and swelling during charging and discharging. Can be. If the amount of residual lithium by-products is 0.3 wt% or less, there is a lack of lithium by-products that react with the coating source to form a coating layer, making it difficult to form a coating layer, and the coating source may act as a resistor, and when the amount exceeds 1 wt%, Lithium by-products can lead to capacity and lifetime inferiority and gas evolution.

In addition, the cathode active material according to the present invention may have a crystal density of 4.76 g / cm ^{3 or} more. More preferably 4.765 g / cm ^{3 or} more. Conventional high-concentration nickel-containing positive electrode active material has a significant decrease in structure stability and high temperature stability after washing with water, but the positive electrode active material according to the present invention has a crystal density due to recrystallization of metal elements by high temperature heat treatment in an oxygen atmosphere after washing with water. Can increase to 4.76 g / cm ³ or more. Through this, the calorific value is significantly reduced, and the high temperature life characteristics and the high temperature resistance increase rate can be significantly improved.

In addition, the cathode active material according to the present invention may have a BET specific surface area of 0.5 m ² / g or less. Conventional high-concentration nickel-containing positive electrode active material, while the lithium in the surface crystal structure withdraws through the water, the specific surface area is significantly increased and the structural stability and high temperature stability is deteriorated, but the positive electrode active material according to the present invention is a high temperature heat treatment in an oxygen atmosphere after water washing As a result, the specific surface area may be reduced to 0.5 m ² / g or less, more preferably 0.35 m ² / g or less due to recrystallization of the metal elements. Through this, the calorific value is significantly reduced, and the high temperature life characteristics and the high temperature resistance increase rate can be significantly improved.

In addition, the positive electrode active material according to the present invention, when measured the heat flow (Heat Flow) by differential scanning calorimetry (DSC), the maximum temperature in the temperature range of 220 ℃ to 250 ℃, preferably 225 ℃ to 245 ℃ A peak may appear and the maximum value of the heat flow may be 200 mW or less (based on a sample of 15 mg). If the high temperature heat treatment is not performed after washing with water or if the heat treatment temperature and atmosphere do not satisfy the conditions of the present invention even after high temperature heat treatment, the maximum peak appears at a lower temperature, that is, less than 220 ° C., and a high heat flow value exceeding 200 mW (sample 15 mg standard). As described above, when the maximum peak appears in the low temperature range and the cathode active material having a high maximum heat flow amount is used, when the temperature inside the battery increases due to overcharging or the like, an explosion may occur while the heat flow rate increases rapidly. On the other hand, since the positive electrode active material of the present invention has a relatively high temperature range in which the maximum peak appears and a small maximum amount of heat flow, the explosion risk is small even when the internal temperature of the battery increases due to overcharge or the like.

In addition, the cathode active material according to the present invention may include the lithium transition metal oxide in a layered structural phase and a spinel-like structural phase. The spinel-like structure phase may be formed by a phase transition from the layered structure phase. The phase transition may occur by high temperature heat treatment.

According to another embodiment of the present invention, a cathode including the cathode active material is provided.

Specifically, the positive electrode includes a positive electrode current collector and a positive electrode active material layer positioned on at least one surface of the positive electrode current collector and including the positive electrode active material.

The positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, carbon, nickel, titanium on the surface of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface treated with silver, silver or the like can be used. In addition, the positive electrode current collector may have a thickness of about 3 to 500 μm, and may form fine irregularities on the surface of the current collector to increase the adhesion of the positive electrode active material. For example, it can be used in various forms, such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven body.

The cathode active material layer may include a conductive material and a binder together with the cathode active material described above.

At this time, the positive electrode active material may be included in the weight of 80 to 99% by weight, more specifically 85 to 98% by weight relative to the total weight of the positive electrode active material layer. When included in the above content range may exhibit excellent capacity characteristics.

In this case, the conductive material is used to impart conductivity to the electrode. In the battery constituted, the conductive material may be used without particular limitation as long as it has electronic conductivity without causing chemical change. Specific examples thereof include graphite such as natural graphite and artificial graphite; Carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black and carbon fiber; Metal powder or metal fibers such as copper, nickel, aluminum, and silver; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Or conductive polymers such as polyphenylene derivatives, and the like, or a mixture of two or more kinds thereof may be used. The conductive material may be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

The binder serves to improve adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC). ), Starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubbers, or various copolymers thereof, and the like, and one or a mixture of two or more thereof may be used. The binder may be included in an amount of 1 to 30% by weight based on the total weight of the positive electrode active material layer.

The positive electrode may be manufactured according to a conventional positive electrode manufacturing method except for using the positive electrode active material described above. Specifically, the positive electrode active material and optionally, a composition for forming a positive electrode active material layer prepared by dissolving or dispersing a binder and a conductive material in a solvent may be applied onto a positive electrode current collector, followed by drying and rolling. In this case, the type and content of the cathode active material, the binder, and the conductive material are as described above.

The solvent may be a solvent generally used in the art, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone or acetone. Water, and the like, one of these alone or a mixture of two or more thereof may be used. The amount of the solvent is sufficient to dissolve or disperse the positive electrode active material, the conductive material, and the binder in consideration of the coating thickness of the slurry and the production yield, and to have a viscosity that can exhibit excellent thickness uniformity during application for the production of the positive electrode. Do.

Alternatively, the positive electrode may be prepared by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating the film obtained by peeling from the support onto a positive electrode current collector.

According to another example of the present invention, an electrochemical device including the anode is provided. The electrochemical device may be specifically a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned to face the positive electrode, a separator and an electrolyte interposed between the positive electrode and the negative electrode, and the positive electrode is as described above. The lithium secondary battery may further include a battery container for accommodating the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container.

In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. For example, the negative electrode current collector may be formed on a surface of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper, or stainless steel. Surface-treated with carbon, nickel, titanium, silver, and the like, aluminum-cadmium alloy and the like can be used. In addition, the negative electrode current collector may have a thickness of 3 μm to 500 μm, and similarly to the positive electrode current collector, fine concavities and convexities may be formed on the surface of the current collector to enhance the bonding force of the negative electrode active material. For example, it can be used in various forms, such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven body.

The negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fibers, and amorphous carbon; Metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys or Al alloys; Metal oxides capable of doping and undoping lithium, such as SiO _β (0 <β <2), SnO ₂ , vanadium oxide, and lithium vanadium oxide; Or a composite including the metallic compound and the carbonaceous material, such as a Si-C composite or a Sn-C composite, and any one or a mixture of two or more thereof may be used. In addition, a metal lithium thin film may be used as the anode active material. As the carbon material, both low crystalline carbon and high crystalline carbon can be used. Soft crystalline carbon and hard carbon are typical low crystalline carbon, and high crystalline carbon is amorphous, plate, scaly, spherical or fibrous natural graphite or artificial graphite, Kish graphite (Kish) graphite, pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch High-temperature calcined carbon such as derived cokes is typical.

In addition, the binder and the conductive material may be the same as described above in the positive electrode.

The negative electrode active material layer is, for example, coated with a negative electrode active material, and optionally a composition for forming a negative electrode active material layer prepared by dissolving or dispersing a binder and a conductive material in a solvent and dried, or for forming the negative electrode active material layer The composition may be prepared by casting the composition on a separate support, and then laminating the film obtained by peeling from the support onto a negative electrode current collector.

On the other hand, in the lithium secondary battery, the separator is to separate the negative electrode and the positive electrode and to provide a passage for the movement of lithium ions, if it is usually used as a separator in a lithium secondary battery can be used without particular limitation, in particular for ion transfer of the electrolyte It is desirable to have a low resistance against the electrolyte and excellent electrolytic solution-moisture capability. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer or the like Laminate structures of two or more layers may be used. In addition, conventional porous nonwoven fabrics such as nonwoven fabrics made of high melting point glass fibers, polyethylene terephthalate fibers and the like may be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may be optionally used as a single layer or a multilayer structure.

In addition, examples of the electrolyte used in the present invention include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, and the like, which can be used in manufacturing a lithium secondary battery. It doesn't happen.

Specifically, the electrolyte may include an organic solvent and a lithium salt.

The organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may be an ester solvent such as methyl acetate, ethyl acetate, γ-butyrolactone or ε-caprolactone; Ether solvents such as dibutyl ether or tetrahydrofuran; Ketone solvents such as cyclohexanone; Aromatic hydrocarbon solvents such as benzene and fluorobenzene; Dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate, Carbonate solvents such as PC); Alcohol solvents such as ethyl alcohol and isopropyl alcohol; Nitriles, such as R-CN (R is a C2-C20 linear, branched or cyclic hydrocarbon group, which may include a double bond aromatic ring or an ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; Or sulfolanes may be used. Of these, carbonate-based solvents are preferable, and cyclic carbonates having high ionic conductivity and high dielectric constant (for example, ethylene carbonate or propylene carbonate) that can improve the charge and discharge performance of a battery, and low viscosity linear carbonate compounds ( For example, a mixture of ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate and the like is more preferable. In this case, the cyclic carbonate and the chain carbonate may be mixed and used in a volume ratio of about 1: 1 to about 1: 9, so that the performance of the electrolyte may be excellent.

The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (C ₂ F ₅ SO ₃ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ . LiCl, LiI, or LiB (C ₂ O ₄ ) ₂ and the like can be used. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0M. When the concentration of the lithium salt is included in the above range, since the electrolyte has an appropriate conductivity and viscosity, it can exhibit excellent electrolyte performance, and lithium ions can move effectively.

In addition to the electrolyte components, the electrolyte includes, for example, haloalkylene carbonate-based compounds such as difluoro ethylene carbonate, pyridine, tri, etc. for the purpose of improving battery life characteristics, reducing battery capacity, and improving discharge capacity of the battery. Ethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N, N-substituted imida One or more additives such as zolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol or aluminum trichloride may be included. In this case, the additive may be included in 0.1 to 5% by weight based on the total weight of the electrolyte.

As described above, since the lithium secondary battery including the cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, portable devices such as mobile phones, notebook computers, digital cameras, and hybrid electric vehicles ( It is useful for electric vehicle fields such as hybrid electric vehicle (HEV).

Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

The battery module or the battery pack is a power tool (Power Tool); Electric vehicles including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); Or it can be used as a power source for any one or more of the system for power storage.

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be cylindrical, square, pouch type, or coin type using a can.

The lithium secondary battery according to the present invention may not only be used in a battery cell used as a power source for a small device, but also preferably used as a unit battery in a medium-large battery module including a plurality of battery cells.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily practice the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

Example 1

Lithium transition metal oxide is _{Li (Ni 0. 86 Co 0} . 1 Mn 0. 02 Al 0. 02) O 2 300 g of pure water was added to 240 mL of water, stirred for 30 minutes, and washed for 20 minutes. The filtered lithium transition metal oxide was dried at 130 ° C. in a vacuum oven, followed by sieving.

Then, the washed lithium transition metal oxide was subjected to high temperature heat treatment in an oxygen atmosphere with an oxygen partial pressure of 95%. At this time, the temperature was raised to 700 ° C. at 5 ° C./min for 2 hours and 15 minutes, and heat-treated at 700 ° C. for 3 hours and 40 minutes, and then heated at a high temperature for 2 hours and 30 minutes.

Next, after mixing 1.0 wt% of H ₃ BO ₃ with B content based on the high temperature heat-treated lithium transition metal oxide, coating heat treatment was performed at 300 ° C. under a dry air atmosphere for 5 hours to prepare a cathode active material.

Example 2

Except that the high temperature heat treatment was heated to 600 ℃ for 2 hours 20 minutes at 4 ℃ / min, heat treatment for 3 hours 40 minutes at 600 ℃, and the high temperature heat treatment by cooling for 2 hours 30 minutes Example 1 The positive electrode active material was prepared in the same manner as the above.

Comparative Example 1

Except not performing a high temperature heat treatment was carried out in the same manner as in Example 1 to prepare a positive electrode active material.

Comparative Example 2

The high temperature heat treatment was carried out in the same manner as in Example 1 except that the temperature was raised to 200 ℃ for 45 minutes, the heat treatment at 200 ℃ for 10 hours, the cooling process for 60 minutes to prepare a positive electrode active material.

Comparative Example 3

The cathode active material was prepared in the same manner as in Example 1 except that the mixture was heated to 300 ° C. for 70 minutes, heat-treated at 300 ° C. for 3 hours and 40 minutes, and cooled at 90 ° C. for 90 minutes. It was.

Comparative Example 4

The high temperature heat treatment was carried out in the same manner as in Example 1 except that the temperature was raised to 400 ℃ for 80 minutes, the heat treatment for 4 hours at 400 ℃, and the high temperature heat treatment for 2 hours to prepare a cathode active material.

Comparative Example 5

A high temperature heat treatment was carried out in the same manner as in Example 1 except that the temperature was elevated to 500 ° C. for 90 minutes, heat treated at 500 ° C. for 4 hours, and cooled for 2 hours and 20 minutes to prepare a cathode active material. It was.

Comparative Example 6

The high temperature heat treatment was carried out in the same manner as in Example 1 except that the temperature was raised to 700 ℃ for 3 hours, the heat treatment for 10 hours at 700 ℃, and the high temperature heat treatment for 3 hours to prepare a cathode active material.

Comparative Example 7

A positive electrode active material was prepared in the same manner as in Example 1 except that the high temperature heat treatment was performed in an air atmosphere instead of an oxygen atmosphere.

Experimental Example 1: XRD Analysis by Process]

The cathode active materials prepared in Example 1 and Comparative Example 1 were analyzed by XRD using Bruker AXS D4 Endeavor XRD, and the crystal size, crystal density, and Ni cations in the lithium layer were analyzed. The results of cation mixing are shown in Table 1. In addition, the BET surface area was measured using BELSORP-mini, the results are shown in Table 1.

	fair	Cation mixing (%)	Crystal Density (g / cm 3 )	Crystal size (nm)	BET surface area (m 2 / g)
Example 1	Before washing	1.0	4.773	181	0.27
	Defensive	1.4	4.757	182	1.51
	High temperature heat treatment	1.1	4.768	173	0.33
	Coating heat treatment	1.0	4.768	154	0.32
Comparative Example 1	Flush-coating heat treatment	1.4	4.722	159	0.68

Referring to Table 1, it can be seen that in Example 1 subjected to high temperature heat treatment according to the present invention, the amount of cation mixture was decreased, the crystal density was increased, and the BET specific surface area was reduced compared to Comparative Example 1, which was not subjected to high temperature heat treatment. .

Experimental Example 2: Evaluation of Residual By-Products of Lithium

10 g of the positive electrode active material prepared according to Examples and Comparative Examples was dispersed in 100 mL of water, and titrated with 0.1 M HCl to measure a change in pH value to obtain a pH titration curve. Residual LiOH and Li ₂ CO _{3 in the} positive electrode active material were calculated using the pH titration curve, and the sum of these values was evaluated as the total amount of lithium byproduct.

	Residual LiOH (wt%)	Residual amount of Li 2 CO 3 (wt%)	Total Lithium By-Product Residues (wt%)
Example 1	0.234	0.070	0.304
Example 2	0.278	0.171	0.449
Comparative Example 1	0.356	0.200	0.556
Comparative Example 2	0.211	0.334	0.545
Comparative Example 3	0.246	0.272	0.518
Comparative Example 4	0.328	0.305	0.633
Comparative Example 5	0.360	0.236	0.596
Comparative Example 6	0.305	0.214	0.519
Comparative Example 7	0.779	0.605	1.384

Referring to Table 2, the content of residual lithium by-products was significantly reduced in Examples 1 and 2 compared to Comparative Example 1 without high temperature heat treatment or Comparative Examples 2 to 6 not satisfying high temperature heat treatment conditions of the present invention. , In Comparative Example 7 heat-treated in the air atmosphere it can be seen that the content of the residual lithium by-products further increased compared to Comparative Example 1 not subjected to high temperature heat treatment.

Experimental Example 3: Evaluation of Heat Flow Rate

Differential scanning calorimetry (SETENRAM SENSYS Evo) was used to measure the heat flow (Heat Flow) according to the temperature of the positive electrode active materials of Examples and Comparative Examples. 15 mg of a 4.25V charged electrode was collected, and 20 µl of the electrolyte was added, and then measured up to 400 ° C. at a temperature rising rate of 10 ° C. per minute.

The measurement result is shown in FIG.

Referring to FIG. 1, the positive electrode active materials of Examples 1 and 2 have a maximum heat flow value of less than 200 mW, whereas the positive active materials of Comparative Examples 1 to 7 have a maximum heat flow value of more than 400 mW, and particularly, in the case of Comparative Example 1, 600 mW. It can be confirmed that the excess. This shows that the positive electrode active materials of Examples 1 and 2 have excellent high temperature stability compared to the positive electrode active materials of Comparative Examples 1 to 7.

Experimental Example 4: Battery Performance Evaluation

Each positive electrode active material, carbon black conductive material, and PVdF binder prepared in Examples and Comparative Examples were mixed in an N-methylpyrrolidone solvent in a ratio of 95: 2.5: 2.5 by weight in a positive electrode mixture (viscosity: 5000 mPa · s ) Was applied to one surface of an aluminum current collector, dried at 130 ° C., and then rolled to prepare a positive electrode.

In addition, as a negative electrode active material, a natural graphite, a carbon black conductive material, and a PVdF binder were mixed in an N-methylpyrrolidone solvent in a ratio of 85: 10: 5 in a weight ratio to prepare a composition for forming a negative electrode active material layer, and a copper current collector It was applied to one side of to prepare a negative electrode.

An electrode assembly was manufactured between the positive electrode and the negative electrode prepared as described above through a separator of porous polyethylene, the electrode assembly was placed in a case, and an electrolyte solution was injected into the case to prepare a lithium secondary battery. At this time, the electrolyte is prepared by dissolving 1.0M concentration of lithium hexafluorophosphate (LiPF ₆ ) in an organic solvent consisting of ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate (mixing volume ratio of EC / DMC / EMC = 3/4/3). It was.

Capacity retention rate (%) and resistance increase rate of the lithium secondary battery prepared as described above while performing 30 cycles of charge and discharge at 45 ° C. under a charge end voltage of 4.25V, a discharge end voltage of 2.5V, and 0.3C / 0.3C. (DCIR [%]) was measured. The measurement results are shown in FIGS. 2 and 3. 2 is a graph showing a capacity retention rate, and FIG. 3 is a graph showing a resistance increase rate.

2 and 3, in the secondary batteries to which the cathode active materials of Examples 1 and 2 are applied, the capacity reduction rate and the resistance increase rate are remarkable at 30 charge / discharge cycles compared to the secondary batteries to which the cathode active materials of Comparative Examples 1 to 7 are applied. It can be confirmed that the low temperature life characteristics and resistance characteristics are improved.

Claims (20)

1. Preparing a lithium transition metal oxide including nickel (Ni) and cobalt (Co) and including at least one selected from the group consisting of manganese (Mn) and aluminum (Al);

   Washing the lithium transition metal oxide to remove lithium impurities present on the surface of the lithium transition metal oxide; And

   And heat-treating the lithium transition metal oxide after washing with water.

   The high temperature heat treatment may include a temperature increase section for increasing the temperature and heat treatment, a maintenance section for maintaining the elevated temperature, and a cooling section for cooling the temperature, wherein the temperature increase section includes 20 to 30 degrees for the entire high temperature heat treatment time. Method for producing a positive electrode active material for secondary batteries which is%.
2. The method of claim 1,

   The holding section is a method of manufacturing a positive electrode active material for a secondary battery is 40 to 50% of the total high temperature heat treatment time.
3. The method of claim 1,

   The cooling section is a method of manufacturing a positive electrode active material for secondary batteries 20 to 30% of the total high temperature heat treatment time.
4. The method of claim 1,

   The total high temperature heat treatment time is 6 to 10 hours manufacturing method of the positive electrode active material for secondary batteries.
5. The method of claim 1,

   The heat treatment temperature of the holding section is 600 to 900 ℃ the manufacturing method of the positive electrode active material for secondary batteries.
6. The method of claim 1,

   The temperature increase rate of the temperature increase interval is 2 to 7 ℃ / min method for producing a positive electrode active material for secondary batteries.
7. The method of claim 1,

   The cooling section is a method of manufacturing a positive active material for a secondary battery to be naturally cooled.
8. The method of claim 1,

   The high temperature heat treatment is a method of manufacturing a positive electrode active material for a secondary battery performed in an oxygen atmosphere with an oxygen partial pressure of 80% or more.
9. The method of claim 1,

   The washing method is a method of manufacturing a positive electrode active material for a secondary battery performed using 50 to 100 parts by weight of pure water with respect to 100 parts by weight of the lithium transition metal oxide.
10. The method of claim 1,

    The washing method is a method of manufacturing a cathode active material for a secondary battery performed at a temperature of -10 to 30 ℃.
11. The method of claim 1,

    The lithium transition metal oxide is a method of manufacturing a positive electrode active material for a secondary battery represented by the following formula (1).

    [Formula 1]

    Li _a Ni _{1 -x1-y1- z1} Co _x1 M ¹ _y1 M ² _z1 M ³ _q1 O ₂

    (In Formula 1,

    M ¹ is at least one or more selected from the group consisting of Mn and Al,

    M ² and M ³ is each independently at least one or more selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb, W, and Mo,

    1.0≤a≤1.5, 0 <x1≤0.2, 0 <y1≤0.2, 0≤z1≤0.1, 0≤q1≤0.1, 0 <x1 + y1 + z1≤0.2.)
12. The method of claim 1,

    Preparing the lithium transition metal oxide,

    A method of manufacturing a cathode active material for a secondary battery, which is performed by mixing a precursor represented by Chemical Formula 2 and a lithium-containing raw material and firing at 700 to 900 ° C.

    [Formula 2]

    Ni _{1 - x2 -y2- z2} Co _x2 M ¹ _y2 M ² _z2 (OH) ₂

    (In Formula 2,

    M ¹ is at least one or more selected from the group consisting of Mn and Al,

    M ² is at least one or more selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb, W and Mo,

    0 <x2≤0.2, 0≤y2≤0.2, 0≤z2≤0.1, 0 <x2 + y2 + z2≤0.2.)
13. The method of claim 1,

    The high temperature heat-treated lithium transition metal oxide and at least one selected from the group consisting of H ₃ BO ₃ , B ₂ O ₃ and Al ₂ O ₃ are mixed, followed by heat treatment at a temperature of 200 to 500 ℃ surface of the lithium transition metal oxide Forming a coating layer on the;

    Method of manufacturing a positive electrode active material for a secondary battery further comprising.
14. Nickel (Ni), cobalt (Co), including a lithium transition metal oxide containing at least one selected from the group consisting of manganese (Mn) and aluminum (Al),

    The lithium transition metal oxide has a content of nickel (Ni) of at least 80 mol% of the total transition metal elements,

    The positive electrode active material for secondary batteries, wherein a cation mixing ratio of Ni cations in the lithium layer in the lithium transition metal oxide structure is 1.1% or less.
15. The method of claim 14,

    The positive electrode active material for secondary batteries, wherein the lithium by-product content present in the positive electrode active material is more than 0.3% by weight to 1% by weight or less.
16. The method of claim 14,

    The lithium transition metal oxide includes a layered structural phase and a spinel-like structural phase.
17. The method of claim 14,

    Crystal active material of the positive electrode active material (crystal density) is 4.76 g / cm ³ or more positive electrode active material for secondary batteries.
18. The method of claim 14,

    The positive electrode active material for secondary batteries whose BET specific surface area of the said positive electrode active material is 0.5 m <^2> / g or less.
19. The positive electrode for secondary batteries containing the positive electrode active material for secondary batteries of any one of Claims 14-18.
20. A lithium secondary battery comprising the anode for secondary battery of claim 19.

Images