KR20240048709A - Method for preparing positive electrode active material and positive electrode active material - Google Patents

Abstract

The present invention relates to a method for manufacturing a positive electrode active material, which secures the initial efficiency and stability of the lithium manganese rich positive electrode active material through doping of a specific element, while preventing drying problems that may occur when manufacturing the lithium manganese rich positive electrode active material by the Pezzini method. It relates to a method for manufacturing a positive electrode active material that solves problems that may occur during spray drying through spray drying, and to a positive electrode active material manufactured therefrom.

Description

Cathode active material manufacturing method and cathode active material {METHOD FOR PREPARING POSITIVE ELECTRODE ACTIVE MATERIAL AND POSITIVE ELECTRODE ACTIVE MATERIAL}

The present invention relates to a method for producing a positive electrode active material and a positive electrode active material manufactured therefrom.

Recently, the demand for high-capacity secondary batteries has increased due to technological developments such as electric vehicles, and accordingly, research on cathodes using high-nickel (High Ni) cathode active materials with excellent capacity characteristics has been actively conducted. However, in the case of high nickel positive electrode active materials, there is a problem of increased manufacturing costs due to the use of cobalt and excessive nickel.

Accordingly, lithium manganese-rich cathode materials with a layered structure in which the manganese content is higher than the nickel content are receiving attention as next-generation cathode materials. This has the advantage of not only being cheaper than existing high nickel positive electrode active materials, but also having a high discharge capacity of over 250 mAh/g and being able to operate at high voltage. This lithium manganese rich cathode material is composed of manganese and nickel, which are redox active transition metals, and consists of two phases, Li ₂ MnO ₃ and LiMnO ₂ , and is driven by high voltage formation. It is activated through, and at this time, Li ⁺ ions are extracted, oxygen evolution (O ₂ evolution) occurs, and LiO ₂ or Li _x MnO ₂ with excellent electrical conductivity is generated, resulting in high capacity. In addition, lithium manganese rich cathode materials can operate stably at high temperatures and have relatively little decomposition.

However, due to the structural characteristics of the lithium manganese rich cathode material, which is a layered structure, it not only causes voltage fade, gas generation, and structural change to a spinel structure during the cycle, but also causes capacity loss in the first cycle and There is a problem with limited cycle life.

The problem to be solved by the present invention is to secure the initial efficiency and stability of the lithium manganese rich cathode active material through doping of a specific element in manufacturing the lithium manganese rich cathode active material, and to eliminate the problems that occur in each process when manufacturing the lithium manganese rich cathode active material. The goal is to solve all possible problems.

In other words, the present invention was developed to solve the problems of the prior art, and while securing the initial efficiency and stability of the lithium manganese rich positive electrode active material through doping of a specific element, when manufacturing the lithium manganese rich positive electrode active material by the Pezzini method, The purpose is to provide a method for manufacturing a positive electrode active material that solves drying problems that may occur through spray drying and also solves problems that may occur during spray drying.

In order to solve the above problems, the present invention provides a method for producing a positive electrode active material and a positive electrode active material manufactured therefrom.

(1) The present invention includes the step of preparing a synthetic solution by mixing lithium raw material, nickel raw material, manganese raw material, potassium doped raw material, and zirconium doped raw material (S10); Producing a dried product by spray drying the synthetic solution prepared in the step (S10) (S20); A step (S30) of producing a plastic product by first firing the dried product manufactured in the step (S20); and a step (S40) of producing a fired product by secondary firing the fired product prepared in the step (S30) in the presence of lithium chloride.

(2) The present invention provides a method for producing a positive electrode active material in (1) above, wherein the mixing in step (S10) is performed by the Pezzini method.

(3) The present invention provides a method for producing a positive electrode active material according to (1) or (2) above, wherein the spray drying in the step (S20) is performed at a temperature of 150 ℃ or more and 200 ℃ or less.

(4) The present invention is a method for producing a positive electrode active material according to any one of (1) to (3) above, wherein the first calcination in the step (S30) is performed at 400 ℃ to 500 ℃ for 3 hours to 6 hours. provides.

(5) The present invention provides a method for producing a positive electrode active material according to any one of (1) to (4) above, wherein the step (S40) is performed by performing secondary firing in a mixed state of the calcined product and lithium chloride. do.

(6) In the present invention, in any one of (1) to (5) above, in the step (S40), the lithium chloride is used in an amount of 0.1 to 2.0 parts by weight based on 100 parts by weight of the total raw materials mixed in the step (S10). A method for manufacturing a positive electrode active material is provided in which the positive electrode active material is added in an amount of parts by weight.

(7) The present invention is a method for producing a positive electrode active material according to any one of (1) to (6) above, wherein the secondary calcination in step (S40) is performed at 800 ℃ to 1,000 ℃ for 10 to 12 hours. provides.

(8) The present invention provides a positive electrode active material containing a lithium transition metal complex oxide containing lithium, nickel, manganese, potassium, zirconium, and chlorine.

(9) The present invention provides the positive electrode active material according to (8) above, wherein the lithium transition metal complex oxide has a layered structure.

(10) The present invention provides the positive electrode active material according to (8) or (9) above, wherein the lithium transition metal complex oxide has an average composition represented by the following formula (1).

[Formula 1]

Li _a K _b Ni _c Mn _d Zr _e O _2-f Cl _f

In Formula 1,

1.10<a<1.30, 0.005<b<0.03, 0.20<c<0.30, 0.50<d<0.65, 0.001<e<0.05 and 0.001<f<0.3, a+b+c+d+e=2.

(11) The present invention according to any one of (8) to (10) above, wherein the lithium transition metal composite oxide has a peak with the strongest peak intensity among the peaks in which 2θ appears at 40° to 50° in XRD. A positive electrode active material without peak splitting is provided.

(12) The present invention provides a positive electrode containing the positive electrode active material according to any one of (8) to (11) above.

(13) The present invention provides a lithium secondary battery including the positive electrode according to (12) above.

According to the method for producing a positive electrode active material of the present invention, it is possible to produce a lithium manganese-rich positive electrode active material that has excellent initial efficiency and stability and does not generate secondary phases.

범위를 확대 및 스피넬 구조의 피크를 표시하여 나타낸 XRD 데이터이다.Figure 1 shows XRD data for the positive electrode active material prepared in Examples 1 to 4 and Comparative Example 1 of the present invention, and Figure 2 shows XRD data from 35° to 50° 2 of the XRD data shown in Figure 1.

This is XRD data shown by expanding the range and displaying the peak of the spinel structure.

Hereinafter, the present invention will be described in more detail to facilitate understanding of the present invention.

Terms or words used in the description and claims of the present invention should not be construed as limited to their usual or dictionary meanings, and the inventor must appropriately use the concepts of terms to explain his invention in the best way. Based on the principle of definability, it must be interpreted with meaning and concept consistent with the technical idea of the present invention.

In the present invention, the term 'lithium manganese rich phase' refers to a phase with a layered rock salt structure based on the Li ₂ MnO ₃ phase, and the 'secondary phase' refers to the LiMn ₂ O ₄ phase. It refers to a phase based on a spinel structure.

Cathode active material manufacturing method

The present invention provides a method for manufacturing a positive electrode active material. The positive electrode active material may be a lithium manganese rich positive electrode active material. For example, the lithium manganese rich positive electrode active material can be manufactured from a solution in which raw materials are mixed all at once by the Pezzini method. However, the synthetic solution synthesized by the Pezzini method has a problem in that the volume of the dried product expands as solvents such as water evaporate during drying, resulting in a rapid decrease in yield to volume during mass production through scale-up. The drying problem that occurs when drying the synthetic solution can be solved through spray drying, which evaporates solvents such as water at the same time as spraying. However, when spray drying is performed, drying is performed from spherical droplets, so the surface area of the dried product increases. Therefore, products dried by spray drying based on the same sintering temperature have the problem of intensified volatilization of lithium due to the increased surface area, and as a result, there is a problem of secondary phases occurring in the manufactured positive electrode active material. Accordingly, the present invention not only has excellent initial efficiency and stability, but also solves the drying problem through spray drying when manufacturing a lithium manganese rich positive electrode active material from a synthetic solution synthesized by the Pezzini method, and also solves the secondary phase problem through spray drying. A method for manufacturing a positive electrode active material that solves this problem is provided.

According to one embodiment of the present invention, the method for producing a positive electrode active material includes preparing a synthetic solution by mixing lithium raw material, nickel raw material, manganese raw material, potassium doped raw material, and zirconium doped raw material (S10); Producing a dried product by spray drying the synthetic solution prepared in the step (S10) (S20); A step (S30) of producing a plastic product by first firing the dried product manufactured in the step (S20); And it may include a step (S40) of producing a fired product by secondary firing the fired product prepared in the step (S30) in the presence of lithium chloride.

According to one embodiment of the present invention, step (S10) is a step of mixing all raw materials including lithium raw materials at once, and mixing in step (S10) may be performed by the Pezzini method. The Pezzini method is a method for synthesizing substances through drying after dissolving all solutes in a solvent such as water at once. Unlike the coprecipitation method, it is a method that allows simultaneous synthesis if the solutes are dissolved in a solvent such as water. Therefore, unlike the coprecipitation method, the positive electrode active material according to the present invention can be synthesized at once with lithium raw materials, transition metal raw materials, and doping raw materials, which has the advantage of shortening the process. In addition, in the case of the Pezzini method as in the present invention, it is similar to the solid-phase synthesis method in that lithium raw materials are synthesized at once, but unlike the solid-phase synthesis method, a solvent such as water is used, and unlike the solid-phase synthesis method, There is an advantage that synthesis is possible through uniform mixing between each raw material, even without mixing by applying a large amount of energy.

According to one embodiment of the present invention, the lithium raw material may be lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, for example, Li ₂ CO ₃ , LiNO ₃ , LiNO ₂ , LiOH, LiOH·H ₂ O, LiH, LiF, LiCl, LiBr, LiI, CH ₃ COOLi, Li ₂ O, Li ₂ SO ₄ , CH ₃ COOLi, Li ₃ C ₆ H ₅ O ₇ or mixtures thereof may be used, and a specific example may be lithium acetate.

According to one embodiment of the present invention, the nickel raw material and the manganese raw material may include acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or oxyhydroxide of each transition metal. As a specific example, the nickel raw material is Ni(OH) ₂ , NiO, NiOOH, NiCO ₃ ·2Ni(OH) ₂ ·4H ₂ O, NiC ₂ O ₂ ·2H ₂ O, Ni(NO ₃ ) ₂ ·6H ₂ O , NiSO ₄ , NiSO ₄ ·6H ₂ O, fatty acid nickel salt, or nickel halide, and any one or a mixture of two or more of these may be used. A more specific example may be nickel(II) acetate. Additionally, the manganese raw materials include manganese oxides such as Mn ₂ O ₃ , MnO ₂ and Mn ₃ O ₄ ; Manganese salts such as MnCO ₃ , Mn(NO ₃ ) ₂ , MnSO ₄ , manganese acetate, dicarboxylic acid manganese salt, manganese citrate and fatty acid manganese salt; It may be oxyhydroxide or manganese chloride, and any one or a mixture of two or more of these may be used. A more specific example may be manganese(II) acetate.

According to one embodiment of the present invention, the potassium doping raw material and the zirconium doping raw material may be acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or oxyhydroxide of potassium and zirconium, respectively. Specific examples include potassium Acetate and zirconium acetate.

According to one embodiment of the present invention, the potassium doping raw material is for doping lithium sites by substituting potassium. When doping potassium as in the present invention, the ionic radius of potassium is larger than the ionic radius of lithium, The occurrence of secondary phases can be suppressed, and thus initial efficiency and derating can be increased while maintaining structural stability.

According to one embodiment of the present invention, the zirconium doping raw material is used to dope the transition metal site by substituting zirconium. In addition to zirconium, the doping raw material that can improve the initial efficiency of the lithium manganese rich positive electrode active material is limited, Sn may also be considered as a transition metal that can improve initial efficiency, but in the case of Sn, there is a problem of secondary phases occurring when the doping concentration is increased enough to improve initial efficiency.

According to one embodiment of the present invention, the step (S20) is a step for producing a dried product by drying the synthetic solution prepared according to the step (S10), that is, the synthetic solution synthesized according to the Pezzini method. In order to prevent volume expansion of the dried product during drying of the solution, spray drying may be used, and the spray drying in step (S20) may be performed at a temperature of 150°C or more and 200°C or less. As a specific example, the spray drying in step (S20) may be carried out at a temperature of 150 ℃ or higher, 160 ℃ or higher, 170 ℃ or higher, or 180 ℃ or higher, and may also be performed at a temperature of 200 ℃ or lower, 190 ℃ or lower, or 180 ℃ or lower. It can be carried out within this range, while preventing volume expansion of the dried product and maximizing drying efficiency.

According to one embodiment of the present invention, the (S30) step is a step for producing a plastic product by heat treating the dried product, and the first firing in the (S30) step is at 400 ℃ to 500 ℃ for 3 to 6 hours. It can be implemented. As a specific example, the first calcination in the step (S30) may be carried out at a temperature of 400 ℃ or higher, 410 ℃ or higher, 420 ℃ or higher, 430 ℃ or higher, 440 ℃ or higher, or 450 ℃ or higher, and 500 ℃ or lower, 490 ℃ or higher. Hereinafter, it may be carried out at a temperature of 480 ℃ or lower, 470 ℃ or lower, 460 ℃ or lower, or 450 ℃ or lower. In addition, the first firing in the step (S30) may be performed for 3 hours or more, 4 hours or more, or 5 hours or less, and may be performed for 6 hours or less, or 5 hours or less, within the temperature and time range. Structural stability can be improved while suppressing the occurrence of secondary phases.

According to one embodiment of the present invention, the step (S40) is a step for producing a fired product by heat treating the fired product, and may be performed in the presence of lithium chloride to prevent the generation of a secondary phase due to secondary firing. there is. As a specific example, the step (S40) may be performed by secondary calcination in a state where the calcined product and lithium chloride are mixed. The plastic product is manufactured from the dried product by spray drying in step (S20), and has an increased surface area due to volume expansion during drying. Therefore, when secondary firing is performed on the calcined product at a high temperature, volatilization of lithium intensifies, and secondary phases are generated accordingly. However, when the secondary calcination of the calcined product is performed in the presence of lithium chloride, as in the step (S40) above, it is possible to prevent secondary phases from occurring due to volatilization of lithium due to the flux effect caused by lithium chloride. Of course, the particle size can also be improved. Meanwhile, in addition to the above lithium chloride, it is also possible to consider adding other types of lithium halide. However, lithium halide other than lithium chloride does not show a flux effect, so it is expected to prevent secondary phase generation and improve cell performance as much as lithium chloride. It's difficult to do.

According to one embodiment of the present invention, in the step (S40), the lithium chloride may be added in an amount of 0.1 to 2.0 parts by weight based on 100 parts by weight of the total raw materials mixed in the step (S10). As a specific example, the lithium chloride is 0.1 part by weight, 0.2 part by weight, 0.3 part by weight, 0.4 part by weight, 0.5 part by weight, 0.6 part by weight, based on 100 parts by weight of the total raw materials mixed in step (S10). It may be added in an amount of more than 0.7 parts by weight, or less than 2.0 parts by weight, less than 1.9 parts by weight, less than 1.8 parts by weight, less than 1.7 parts by weight, less than 1.6 parts by weight, less than 1.5 parts by weight, or less than 1.45 parts by weight. It can be added in an amount of parts by weight or less, and within this range, the initial capacity can be further improved while preventing the occurrence of secondary phases due to secondary firing.

According to one embodiment of the present invention, the secondary calcination in step (S40) may be performed at 800°C to 1,000°C for 10 to 12 hours. As a specific example, the secondary firing in step (S40) may be carried out at a temperature of 800 ℃ or higher, 810 ℃ or higher, 820 ℃ or higher, 830 ℃ or higher, 840 ℃ or higher, or 850 ℃ or higher, and 1,000 ℃ or lower, 990 ℃. Hereinafter, it may be carried out at a temperature of 980 ℃ or lower, 970 ℃ or lower, 960 ℃ or lower, or 950 ℃ or lower. In addition, the secondary calcination in step (S40) may be performed for 10 hours or more, 10.5 hours or more, or 11 hours or more, and may also be performed for 12 hours or less, and the secondary phase is generated within the temperature and time range. Structural stability can be improved while suppressing .

positive electrode active material

The present invention provides a positive electrode active material. The positive electrode active material may be manufactured according to the positive electrode active material manufacturing method.

According to one embodiment of the present invention, the positive electrode active material may include a lithium transition metal complex oxide containing lithium, nickel, manganese, potassium, zirconium, and chlorine. Here, the positive electrode active material may be a lithium manganese rich positive electrode active material. As a specific example, the lithium transition metal complex oxide may have a layered structure, and as a more specific example, the lithium manganese rich positive electrode active material may have a layered rock salt structure based on Li ₂ MnO ₃ .

According to one embodiment of the present invention, the lithium transition metal complex oxide may have an average composition represented by the following Chemical Formula 1.

[Formula 1]

Li _a K _b Ni _c Mn _d Zr _e O _2-f Cl _f

In Formula 1, 1.10<a<1.30, 0.005<b<0.03, 0.20<c<0.30, 0.50<d<0.65, 0.001<e<0.05 and 0.001<f<0.3, a+b+c+d+e =2.

According to one embodiment of the present invention, in Formula 1, a is the molar ratio of lithium in the lithium transition metal complex oxide, and may be 1.10 or more, 1.11 or more, 1.12 or more, 1.13 or more, 1.14 or more, or 1.15 or more, and, It may be 1.30 or less, 1.25 or less, or 1.20 or less.

According to one embodiment of the present invention, in Formula 1, b is the molar ratio of doped potassium in the lithium transition metal complex oxide, and may be greater than 0.005, greater than 0.006, greater than 0.007, greater than 0.008, greater than 0.009, or greater than 0.01, Additionally, it may be less than 0.03, less than 0.025, less than 0.02, or less than 0.015.

According to an embodiment of the present invention, in Formula 1, c, d, and e may be the molar ratio of nickel (Ni), manganese (Mn), and zirconium, a doping element, in the lithium transition metal complex oxide, respectively. As a specific example, c may be greater than 0.2, greater than 0.21, or greater than 0.22 as the molar ratio of nickel (Ni), and may also be less than 0.3, less than 0.29, less than 0.28, or less than 0.27. The d may be greater than 0.50, greater than 0.51, greater than 0.52, greater than 0.53, greater than 0.54, or greater than 0.55 as the molar ratio of manganese (Mn), and may be less than 0.65, less than 0.64, less than 0.63, less than 0.62, less than 0.60, less than 0.59. , may be 0.58 or less, or 0.67 or less. The e, as the molar ratio of zirconium, may be greater than 0.001, greater than 0.005, greater than 0.01, greater than 0.02, or greater than 0.03, and may also be less than 0.05, less than 0.045, or less than 0.04.

According to one embodiment of the present invention, in Chemical Formula 1, f may be the molar ratio of chlorine in the lithium transition metal complex oxide. As a specific example, f may be greater than 0.001, greater than 0.0015, or greater than 0.0025, and may also be less than 0.3, less than 0.25, less than 0.2, less than 0.15, less than 0.1, less than 0.5, less than 0.1, less than 0.05, or less than 0.01.

According to one embodiment of the present invention, the lithium transition metal complex oxide may be a perlithiated positive electrode active material with a high proportion of lithium, as represented by Chemical Formula 1, and may also be a perlithiated positive electrode active material with a high proportion of manganese among the transition metals. It can be a lithiated manganese-rich positive electrode active material, and has improved energy density and excellent capacity characteristics without containing cobalt.

According to one embodiment of the present invention, the lithium transition metal complex oxide may not include a secondary phase. The secondary phase can be confirmed from XRD measurements on lithium transition metal complex oxide. As a specific example, the XRD measurement was performed by collecting 2 g to 3 g of positive electrode active material particles from the positive active material powder and using Cu-Kα rays (wavelength 1.54 Å) at an acceleration voltage of 40 kV/40 mA and a scan speed of 0.2 °/sec. It can be carried out in a 2θ range of 15 ° to 90 °. When measuring XRD for the lithium transition metal complex oxide of the positive electrode active material, when it contains a secondary phase, the peak showing the strongest peak intensity among the peaks with 2θ appearing at 40 ° to 50 ° is peak splitting. ), and since the positive electrode active material does not contain a secondary phase, peak splitting of the peak showing the strongest peak intensity among the peaks where 2θ appears at 40 ° to 50 ° in XRD does not appear.

anode

The present invention provides a positive electrode containing the above positive electrode active material.

According to one embodiment of the present invention, the positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer may include the positive electrode active material.

According to one embodiment of the present invention, the positive electrode current collector may include a highly conductive metal, and the positive electrode active material layer is easily adhered, but is not particularly limited as long as it is not reactive within the voltage range of the battery. The positive electrode current collector may be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or an aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. Additionally, the positive electrode current collector may typically have a thickness of 3 ㎛ to 500 ㎛, and fine irregularities may be formed 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 films, sheets, foils, nets, porous materials, foams, and non-woven materials.

According to one embodiment of the present invention, the positive electrode active material layer may optionally include a conductive material and a binder along with the positive electrode active material. At this time, the positive electrode active material may be included in an amount of 80% to 99% by weight, more specifically 85% to 98.5% by weight, based on the total weight of the positive electrode active material layer, and can exhibit excellent capacity characteristics within this range. there is.

According to one embodiment of the present invention, the conductive material is used to provide conductivity to the electrode, and can be used without particular limitation as long as it does not cause chemical change and has electronic conductivity in the battery being constructed. Specific examples 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, thermal black, and carbon fiber; Metal powders or metal fibers such as copper, nickel, aluminum, and silver; Conductive tubes such as carbon nanotubes; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Or conductive polymers such as polyphenylene derivatives, etc., of which one type alone or a mixture of two or more types may be used. The conductive material may be included in an amount of 0.1% to 15% by weight based on the total weight of the positive electrode active material layer.

According to one embodiment of the present invention, the binder serves to improve adhesion between positive electrode active material particles and adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylalcohol, polyacrylonitrile, and polymethylmethane. Crylate (polymethymethaxrylate), carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene- Diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and polymers in which hydrogen thereof is substituted with Li, Na, or Ca, or various copolymers thereof Combinations, etc. may be mentioned, and one type of these may be used alone or a mixture of two or more types may be used. The binder may be included in an amount of 0.1% by weight to 15% by weight based on the total weight of the positive electrode active material layer.

According to one embodiment of the present invention, the positive electrode can be manufactured according to a conventional positive electrode manufacturing method except for using the positive electrode active material described above. Specifically, the positive electrode is prepared by dissolving or dispersing the positive electrode active material and optionally a binder, a conductive material, and a dispersant in a solvent, and the composition for forming a positive active material layer is applied to the positive electrode current collector and then dried. and rolling, or by casting the composition for forming the positive electrode active material layer on a separate support and then peeling from this support and laminating the film obtained on the positive electrode current collector.

According to an embodiment of the present invention, the solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, and N-methylpyrrolidone. (NMP), dimethylformamide (DMF), acetone, or water, among which one type alone or a mixture of two or more types may be used. The amount of the solvent used is to dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant in consideration of the application thickness and manufacturing yield of the slurry, and to have a viscosity capable of exhibiting excellent thickness uniformity when applied for subsequent positive electrode production. That's enough.

Lithium secondary battery

The present invention provides a lithium secondary battery including the positive electrode.

According to one embodiment of the present invention, the lithium secondary battery includes the positive electrode; cathode; It may include a separator and an electrolyte interposed between the anode and the cathode. Additionally, the lithium secondary battery may optionally further include a battery container that accommodates the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

According to one embodiment of the present invention, the negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

According to one embodiment of the present invention, the negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, for example, copper, stainless steel, aluminum, nickel, titanium, plastic. Surface treatment of carbon, copper or stainless steel with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector may typically have a thickness of 3 ㎛ to 500 ㎛, and like the positive electrode current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven materials.

According to one embodiment of the present invention, the negative electrode active material layer may optionally include a binder and a conductive material along with the negative electrode active material.

According to one embodiment of the present invention, a compound capable of reversible intercalation and deintercalation of lithium may be used as the negative electrode active material. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; Metallic compounds that can be alloyed with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; Metal oxides that can dope and undope lithium, such as SiOβ (0<β<2), SnO ₂ , vanadium oxide, and lithium vanadium oxide; Alternatively, a composite containing the above-described metallic compound and a carbonaceous material, such as a Si-C composite or Sn-C composite, may be used, and any one or a mixture of two or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Additionally, the carbon material may include both low-crystalline carbon and high-crystalline carbon. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and high-crystalline carbon includes amorphous, plate-shaped, flaky, spherical, or fibrous natural graphite, artificial graphite, and Kish graphite. graphite, pyrolytic carbon, mesophase pitch based carbonfiber, meso-carbon microbeads, mesophase pitches, and petroleum or coal tar pitch derived High-temperature calcined carbon such as cokes is a representative example. The negative electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of the negative electrode active material layer.

According to one embodiment of the present invention, the binder of the negative electrode active material layer is a component that assists the bonding between the conductive material, the active material, and the current collector, and is typically contained in the amount of 0.1% by weight to 10% by weight based on the total weight of the negative electrode active material layer. is added. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, and polytetra. Examples include fluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluorine rubber, and various copolymers thereof.

According to one embodiment of the present invention, the conductive material of the negative electrode active material layer is a component to further improve the conductivity of the negative electrode active material, and is contained in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. may be added. These conductive materials are not particularly limited as long as they have conductivity without causing chemical changes in the battery, and examples include graphite such as natural graphite or artificial graphite; Carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fiber and metal fiber; fluorinated carbon; Metal powders such as aluminum and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

According to one embodiment of the present invention, the negative electrode is manufactured by applying and drying a composition for forming a negative electrode active material layer prepared by dissolving or dispersing the negative electrode active material and optionally the binder and the conductive material in a solvent on the negative electrode current collector, or Alternatively, it can be manufactured by casting the composition for forming the negative electrode active material layer on a separate support, and then lamination of the film obtained by peeling from this support onto the negative electrode current collector.

According to one embodiment of the present invention, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. It can be used without particular restrictions as long as it is normally used as a separator in a lithium secondary battery, and in particular, it can be used for ion movement in the electrolyte. It is desirable to have low resistance and excellent electrolyte moisturizing ability. Specifically, porous polymer films, for example, porous polymer films made of polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer, or these. A laminated structure of two or more layers may be used. In addition, conventional porous nonwoven fabrics, for example, nonwoven fabrics made of high melting point glass fibers, polyethylene terephthalate fibers, etc., may be used. Additionally, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

According to an embodiment of the present invention, the electrolyte may include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, and a molten inorganic electrolyte that can be used when manufacturing a lithium secondary battery. It is not limited to these. As a specific example, the electrolyte may include an organic solvent and a lithium salt.

According to one embodiment of the present invention, 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 includes ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; Ether-based solvents such as dibutyl ether or tetrahydrofuran; Ketone-based solvents such as cyclohexanone; Aromatic hydrocarbon solvents such as benzene and fluorobenzene; Dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC) ), carbonate-based solvents such as; Alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a straight-chain, branched or ring-structured hydrocarbon group having 2 to 20 carbon atoms and may include a double bond aromatic ring or ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; Alternatively, sulfolane, etc. may be used. Among these, carbonate-based solvents are preferable, and cyclic carbonates (e.g., ethylene carbonate or propylene carbonate, etc.) with high ionic conductivity and high dielectric constant that can improve the charging and discharging performance of the battery, and low-viscosity linear carbonate-based compounds ( For example, ethylmethyl carbonate, dimethyl carbonate, diethyl carbonate, etc.) are more preferable.

According to one embodiment of the present invention, the lithium salt can be used without particular limitation as long as it is a compound that can provide lithium ions used in lithium secondary batteries. Specifically, the anions of the lithium salt include F ^- , Cl ^- , Br ^- , I ^- , NO ₃ ^- , N(CN) ₂ ^- , BF ₄ ^- , CF ₃ CF ₂ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , (SF ₅ ) ₃ C ^- , (CF ₃ SO ₂ ) ₃ C ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- , and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- It may be at least one selected from the group consisting of, 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 may be used. The concentration of the lithium salt is preferably used within the range of 0.1 M to 2.0 M. When the concentration of lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, so excellent electrolyte performance can be achieved and lithium ions can move effectively.

According to one embodiment of the present invention, in addition to the electrolyte components, the electrolyte contains halo such as difluoroethylene carbonate for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. Alkylene carbonate compounds, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexanoic acid triamide, nitrobenzene derivatives, sulfur, quinone imine dye, N-substituted oxazoli One or more additives such as dinon, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, or aluminum trichloride may be further included. At this time, the additive may be included in an amount of 0.1% to 5% by weight based on the total weight of the electrolyte.

Since the lithium secondary battery containing the positive electrode active material according to the present invention stably exhibits excellent capacity characteristics, output characteristics, and lifespan characteristics, it is used in portable devices such as mobile phones, laptop computers, and digital cameras, and hybrid electric vehicles. It is useful in the field of electric vehicles such as HEV) and electric vehicles (EV).

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

The lithium secondary battery according to the present invention can not only be used in battery cells used as a power source for small devices, but can also be preferably used as a unit cell in medium to large-sized battery modules containing multiple battery cells.

Accordingly, according to one 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.

According to one embodiment of the present invention, the battery module or battery pack includes a power tool; Electric vehicles, including electric vehicles (EV), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEV); Alternatively, it can be used as a power source for any one or more mid- to large-sized devices among power storage systems.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement it. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein.

Example

Example 1

9.894 g of citric acid as a chelating agent was dissolved in 80 ml of ion-exchanged water. Afterwards, 30.529 g of lithium acetate, 14.930 g of nickel (II) acetate, 36.580 g of manganese (II) acetate, 0.491 g of potassium acetate, and 0.210 g of zirconium acetate were added to the solution and dissolved at 80 ° C to prepare a synthetic solution. . After each raw material was completely dissolved in the synthetic solution, a dried product was prepared by spray drying at 180°C, and the obtained dried product was first fired at 450°C for 5 hours to prepare a plastic product. Next, the calcined product was mixed with 0.3 g of lithium chloride, the calcined product was prepared by secondary firing at 900°C for 12 hours, and sieving was performed to produce lithium nickel manganese composite oxide powder doped with potassium, zirconium, and chlorine. was obtained.

Example 2

In Example 1, the same method as Example 1 was performed except that 0.6 g of lithium chloride was mixed instead of 0.3 g, and lithium nickel manganese composite oxide powder doped with potassium, zirconium, and chlorine was obtained.

Example 3

In Example 1, the same method as Example 1 was performed except that 0.9 g of lithium chloride was mixed instead of 0.3 g, and lithium nickel manganese composite oxide powder doped with potassium, zirconium, and chlorine was obtained.

Example 4

In Example 1, the same method as Example 1 was performed except that 1.2 g of lithium chloride was mixed instead of 0.3 g, and lithium nickel manganese composite oxide powder doped with potassium, zirconium, and chlorine was obtained.

Comparative Example 1

9.894 g of citric acid as a chelating agent was dissolved in 80 ml of ion-exchanged water. Afterwards, 30.529 g of lithium acetate, 14.930 g of nickel (II) acetate, and 36.580 g of manganese (II) acetate were added to the solution and dissolved at 80°C to prepare a synthetic solution. After each raw material was completely dissolved in the synthetic solution, a dried product was prepared by spray drying at 180°C, and the obtained dried product was first fired at 450°C for 5 hours to prepare a plastic product. Next, the calcined product was subjected to secondary firing at 900° C. for 12 hours to prepare a calcined product, and sieving was performed to obtain lithium nickel manganese composite oxide powder.

Comparative Example 2

9.894 g of citric acid as a chelating agent was dissolved in 80 ml of ion-exchanged water. Afterwards, 30.529 g of lithium acetate, 14.930 g of nickel (II) acetate, 36.580 g of manganese (II) acetate, and 0.491 g of potassium acetate were added to the solution and dissolved at 80°C to prepare a synthetic solution. After each raw material was completely dissolved in the synthetic solution, a dried product was prepared by spray drying at 180°C, and the obtained dried product was first fired at 450°C for 5 hours to prepare a plastic product. Next, the calcined product was mixed with 0.3 g of lithium chloride, the calcined product was prepared by secondary calcination at 900°C for 12 hours, and sieving was performed to obtain lithium nickel manganese composite oxide powder doped with potassium and chlorine. did.

Experiment example

Experimental Example 1: XRD analysis

For each positive electrode active material prepared in the above examples and comparative examples, after XRD measurement, each XRD data is shown in Figures 1 and 2.

At this time, the XRD was performed by collecting 2 g to 3 g of positive electrode active material particles from each of the positive electrode active material powders prepared in the examples and comparative examples, and using Cu-Kα line (wavelength 1.54 Å) at an acceleration voltage of 40 kV/ Measurements were made using X-ray diffraction analysis in a 2θ range of 15° to 90° at a scan speed of 0.2°/sec at 40 mA.

Data measured by XRD are relative values and may vary depending on the measuring device and conditions, but the ratio between peak intensities is an absolute value and does not change depending on the measuring device and conditions.

As shown in Figures 1 and 2, the lithium nickel manganese composite oxide, which is the positive electrode active material prepared in Comparative Example 1, shows peak splitting of the peak showing the strongest peak intensity among the peaks where 2θ appears at 40 ° to 50 °, 2 It was confirmed that a car injury had occurred. On the other hand, the lithium nickel manganese composite oxide doped with potassium, zirconium and chlorine, which is the positive electrode active material prepared in Examples 1 to 4 of the present invention, had a layered rock salt structure based on the Li ₂ MnO ₃ phase, which is a lithium manganese rich phase. , peak splitting of the peak showing the strongest peak intensity among the peaks where 2θ appears at 40 ° to 50 ° did not appear, indicating that the secondary phase of the spinel structure based on the LiMn ₂ O ₄ phase did not occur. I was able to confirm. This is because the structural stability of the lithium manganese-rich positive electrode active material is improved by mixing lithium chloride during the secondary firing of the calcined product, even if the spray drying process is performed when manufacturing the positive electrode active material.

Experimental Example 2: ICP analysis

After taking 0.1 g of each positive electrode active material prepared in the above Examples and Comparative Examples, 1.5 ml of 0.1 M hydrochloric acid was added and heated to 80° C. to dissolve the positive electrode active material. Afterwards, a small amount of hydrogen peroxide was added to completely dissolve the positive electrode active material to prepare a solution. Subsequently, the solution was diluted with ion-exchanged water so that the total volume was 30 ml, and this was diluted again 10 times to prepare an analysis sample. Using an ICP device, the ratio of constituent elements present in the analysis sample was measured, and the ratios of lithium, potassium, nickel, manganese, zirconium, and chlorine elements are shown in Table 2 below.

division Li Ni Mn K Zr Cl Example 1 1.1685 0.2272 0.5585 0.0105 0.0370 0.0010 Example 2 1.1798 0.2213 0.5501 0.0091 0.0374 0.0023 Example 3 1.1666 0.2267 0.5588 0.0088 0.0368 0.0023 Example 4 1.1889 0.2614 0.5445 0.0089 0.0381 0.0032 Comparative Example 1 1.1920 0.2410 0.5670 - - -

As shown in Table 1, it was confirmed that the positive electrode active material prepared in Examples 1 to 4 of the present invention was a lithium manganese rich positive electrode active material, contained an excessive amount of lithium and manganese, and was doped with potassium, zirconium, and chlorine. .

In addition, it was confirmed that the positive electrode active material prepared in Comparative Example 1 did not contain any doping raw materials and contained only lithium, nickel, and manganese.

Experimental Example 3: Coin-type half-cell manufacturing and capacity characteristic evaluation

92.5% by weight of the positive electrode active material prepared in the above examples and comparative examples, 3.0% by weight of Super P as a conductive material, and 4.5% by weight of polyvinylidene fluoride (PVDF) as a binder were mixed in N-methylpyrrolidone (NMP) solvent. A positive electrode slurry was prepared. The prepared positive electrode slurry was applied to one side of an aluminum current collector, dried at 130°C, and rolled to prepare a positive electrode.

An electrode assembly was manufactured using a lithium metal electrode as a negative electrode and a porous polyethylene separator between the positive and negative electrodes. Place it inside the battery case and inject an electrolyte solution in which 1 M LiPF ₆ is dissolved in an organic solvent mixed with ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a volume ratio of 3:4:3. A coin-type half cell was manufactured.

Using the coin-type half-cell containing the positive electrode active material of the examples and comparative examples prepared above, charging to 4.65 V at 0.1 C constant current at 45 ° C, and then discharging to 2.0 V at 0.1 C, performed an activation process (formation). This was carried out, and the charging and discharging capacities at this time were measured.

Subsequently, the battery was charged to 4.4 V at 0.1 C constant current at 25°C, and then discharged to 2.5 V at 0.1 C to measure the initial charge and discharge capacity.

The charging and discharging capacities measured at each stage are shown in Table 2 below.

division activation process Initial charge and discharge charging capacity
(mAh/g) discharge capacity
(mAh/g) efficiency
(%) charging capacity
(mAh/g) discharge capacity
(mAh/g) efficiency
(%) Example 1 321.78 266.77 82.90 206.01 187.06 90.80 Example 2 324.99 275.90 84.89 214.95 195.40 90.90 Example 3 324.89 276.65 85.15 216.22 196.92 91.07 Example 4 324.26 278.14 85.78 218.15 199.17 91.30 Comparative Example 1 295.39 274.74 83.87 193.63 176.23 91.01 Comparative Example 2 305.32 263.41 86.28 205.93 186.34 90.49

As shown in Table 2, it was confirmed that the positive electrode active materials prepared in Examples 1 to 4 of the present invention were all excellent in charge capacity, discharge capacity, and initial efficiency. On the other hand, it was confirmed that the positive electrode active material prepared in Comparative Example 1 did not contain a doping element and had poor initial charge capacity and discharge capacity. In addition, the positive electrode active material prepared in Comparative Example 2 had slightly increased charging capacity, discharging capacity, and efficiency compared to Comparative Example 1, but did not contain zirconium among the doping elements, confirming that it was not sufficiently improved compared to Examples 1 to 4. I was able to.

Claims (11)

Preparing a synthetic solution by mixing lithium raw material, nickel raw material, manganese raw material, potassium doped raw material, and zirconium doped raw material (S10);
Producing a dried product by spray drying the synthetic solution prepared in the step (S10) (S20);
A step (S30) of producing a plastic product by first firing the dried product manufactured in the step (S20); and
A method for producing a positive electrode active material comprising a step (S40) of producing a fired product by secondary firing the fired product prepared in the step (S30) in the presence of lithium chloride. According to paragraph 1,
A method for producing a positive electrode active material, wherein the mixing in step (S10) is performed by the Pezzini method. According to paragraph 1,
A method for producing a positive electrode active material, wherein the spray drying in step (S20) is carried out at a temperature of 150 ℃ or more and 200 ℃ or less. According to paragraph 1,
A method for producing a positive electrode active material, wherein the first calcination in the step (S30) is performed at 400 ℃ to 500 ℃ for 3 to 6 hours. According to paragraph 1,
The (S40) step is a method of producing a positive electrode active material in which secondary firing is performed in a mixed state of the calcined product and lithium chloride. According to paragraph 1,
In the step (S40), the lithium chloride is added in an amount of 0.1 to 2.0 parts by weight based on 100 parts by weight of the total raw materials mixed in the step (S10). According to paragraph 1,
A method for producing a positive electrode active material, wherein the secondary calcination in step (S40) is performed at 800 ℃ to 1,000 ℃ for 10 to 12 hours. A positive electrode active material containing a lithium transition metal complex oxide containing lithium, nickel, manganese, potassium, zirconium, and chlorine. According to clause 8,
A positive electrode active material in which the lithium transition metal complex oxide has a layered structure. According to clause 8,
The lithium transition metal complex oxide is a positive electrode active material having an average composition represented by the following formula (1):
[Formula 1]
Li _a K _b Ni _c Mn _d Zr _e O _2-f Cl _f
In Formula 1,
1.10<a<1.30, 0.005<b<0.03, 0.20<c<0.30, 0.50<d<0.65, 0.001<e<0.05 and 0.001<f<0.3, a+b+c+d+e=2. According to clause 8,
The lithium transition metal complex oxide is a positive electrode active material in which there is no peak splitting of the peak showing the strongest peak intensity among the peaks that appear at 2θ at 40 ° to 50 ° in XRD.