Method for manufacturing cathode active material for sodium ion battery

Abstract

This specification relates to a method for manufacturing a positive electrode active material for a sodium ion battery using a refractory box for calcining a precursor material.

Description

Technology Field

[0001] The present specification relates to a method for manufacturing a positive electrode active material for a sodium ion battery, and more specifically, to a method for manufacturing a positive electrode active material for a sodium ion battery that is economically efficient because it can be used one or more times by suppressing the generation of by-products in the refractory box used during the calcination of the precursor material. Background Technology

[0003] Various inorganic compounds are manufactured through heat treatment (calcination) of precursor materials.

[0004] Typically, calcination of a precursor material of an inorganic compound is performed by placing the precursor material in a heat treatment vessel (hereinafter referred to as a 'refractory container') having heat resistance and chemical resistance and heat treating it at a predetermined temperature.

[0005] At this time, the precursor material, which is the compound to be heat-treated (an inorganic compound or its raw material), is loaded inside the refractory case and is fired through heating without coming into direct contact with flames, smoke, etc.

[0006] Accordingly, the above-mentioned refractory casing must essentially ensure stability at the firing temperature of the above-mentioned precursor material, that is, specific heat resistance and chemical resistance.

[0007] A representative example of an inorganic compound manufactured through heat treatment of a precursor material is the positive electrode active material used in lithium batteries.

[0008] Compounds used as cathode active materials for lithium batteries include lithium nickel oxide, lithium cobalt oxide, lithium manganese oxide, or complex oxides thereof (e.g., NCM, NCA-based lithium complex oxides).

[0009] In the case of the positive electrode active material, the transition metal-containing precursor material and the lithium-containing raw material (e.g., LiOH) are loaded into a refractory container and then heat-treated at a temperature of 600 to 1,200°C to be manufactured.

[0010] Accordingly, the refractory casing used in the manufacture of the positive electrode active material is manufactured using high-heat-resistant ceramic materials such as cordierite, mullite, and spinel as the main component to ensure sufficient heat resistance within the heat treatment temperature range described above.

[0011] Meanwhile, the price of lithium, a scarce resource with limited reserves, is rising due to the expansion of the battery industry. Consequently, sodium-ion battery technology utilizing sodium, which can be produced relatively inexpensively, is being developed.

[0012] Positive active materials used in sodium-ion batteries include sodium chromium oxide, sodium iron oxide, and sodium manganese oxide. Similar to positive active materials for lithium batteries, these are manufactured by loading a precursor material and a sodium-containing raw material (e.g., Na2CO3) into a refractory container and then heat-treating them at a high temperature.

[0013] However, there is a problem in that if sodium-containing raw materials are loaded into conventional cordierite-mullite-spinel refractories and fired, the refractories break, making it impossible to manufacture the anode active material. Prior art literature

[0015] Korean Published Patent Application No. 10-2020-0058383 (Published May 27, 2020) Korean Registered Patent Application No. 10-1161139 (Announced July 2, 2012) Korean Registered Patent Application No. 10-1448417 (Published October 7, 2014) The problem to be solved

[0016] One objective of the present specification is to provide a method for manufacturing a positive electrode active material for a sodium ion battery that improves upon the problem of the refractory casing deteriorating and breaking during the calcination of a mixture containing a sodium-containing raw material.

[0017] Another objective of this specification is to reduce side reactions between sodium-containing raw materials and the main components of refractory casings during the manufacture of positive electrode active materials for sodium-ion batteries, thereby Na x -(Al / Si) y -Oz It is to prevent the generation of by-products such as the back.

[0018] In addition, another objective of the present specification is to provide a method for manufacturing a positive electrode active material for a sodium ion battery using a refractory box having sufficient strength to effectively withstand pressure applied to the inner wall of the refractory box or high-temperature firing conditions when a precursor material is loaded into the refractory box and then pressed.

[0019] The purposes of this specification are not limited to those mentioned above, and other purposes and advantages of this specification not mentioned may be understood from the following description and will be more clearly understood by the embodiments of this specification. Furthermore, it will be readily apparent that the purposes and advantages of this specification can be realized by the means and combinations thereof set forth in the claims. means of solving the problem

[0021] According to one aspect of the present specification, a method for manufacturing a positive electrode active material for a sodium ion battery is provided, comprising: (a) a step of preparing a mixture including a sodium-containing raw material and a precursor material; and (b) a step of heat-treating the mixture after loading it into a refractory box, wherein the refractory box comprises a main body having a space for loading the precursor material, and the ratio of the cordierite phase in the main body is less than 1 weight percent.

[0022] In one embodiment, the sodium-containing raw material may be at least one selected from the group consisting of sodium hydroxide, sodium carbonate, sodium nitrate, sodium nitrite, sodium sulfate, sodium sulfite, sodium phosphate, disodium hydrogen phosphite, sodium fluoride, and sodium acetate.

[0023] Meanwhile, the above-mentioned precursor material may include at least one element selected from the group consisting of Ni, Fe, Mn, Co, Cr, Li, Sb, Cr, Cu, Ru, Sr, Ti, Mg, Zn, Zr, Nb, Sn, Sb, and V.

[0024] In another embodiment, the main body may comprise at least one metal oxide selected from spinel, corundum, mullite, spodumene, zircon, quartz, petalite, eucryptite, lithium disilicate, lithium metasilicate, sodium disilicate, sodium metasilicate, forsterite, magnesium metasilicate, alumina, and silicate.

[0025] Here, the spinel content of the main body may be 25% by weight or less.

[0026] In addition, the above main body may have a corundum content of 15% by weight or more.

[0027] Meanwhile, the above main body may have a spodumene content of 45% by weight or more.

[0028] In one embodiment, the porosity of the main body may be 20 volume% or less.

[0029] At this time, the heat treatment can be performed at a maximum temperature of 600 to 1,200°C for 6 to 18 hours.

[0030] Meanwhile, the above positive active material can be represented by the following chemical formula 1:

[0031] [Chemical Formula 1]

[0032] Na w M1 x M2 y M3 z O2

[0033] M1, M2, and M3 are each at least one selected from the group consisting of Ni, Fe, Mn, Co, Cr, Li, Sb, Cr, Cu, Ru, Sr, Ti, Mg, Zn, Zr, Nb, Sn, Sb, and V, and

[0034] 0.5≤w≤1.5, 0≤x≤1, 0≤y≤1, 0≤z≤1, x+y+z=1. Effects of the invention

[0036] According to the present specification, by preventing the refractory casing from reacting with the sodium-containing raw material to form a thermal image, it is possible to manufacture a positive electrode active material for a sodium ion battery one or more times repeatedly.

[0037] In particular, the generation of by-products such as Na-(Al / Si)-O is reduced, thereby improving the durability of the refractory case and further preventing contamination of the manufactured anode active material by said by-products.

[0038] In addition to the effects described above, the specific effects of this specification are described together with the specific details for implementing the matters described in this specification below. Brief explanation of the drawing

[0040] FIG. 1 shows a refractory plate after heat treatment of a positive electrode active material for a sodium ion battery according to one embodiment of the present specification. Specific details for implementing the invention

[0041] For convenience of understanding this specification, specific terms are defined herein. Unless otherwise defined herein, scientific and technical terms used herein shall have the meanings generally understood by those skilled in the art. Furthermore, unless specifically indicated in the context, terms in their singular form shall be understood to include their plural form, and terms in their plural form shall be understood to include their singular form.

[0043] Hereinafter, a method for manufacturing a positive electrode active material for a sodium ion battery according to the present specification will be described in more detail.

[0045] Method for manufacturing a positive electrode active material for a sodium ion battery

[0046] A method for manufacturing a positive electrode active material for a sodium ion battery according to one aspect of the present specification comprises: (a) a step of preparing a mixture comprising a sodium-containing raw material and a precursor material; and (b) a step of heat-treating the mixture after loading it into a refractory box, wherein the refractory box comprises a main body having a space for loading the precursor material, and the ratio of the cordierite phase in the main body may be less than 1 weight%.

[0047] Sodium ion batteries, also known as sodium ion batteries, are a type of secondary battery that can be charged and discharged through the movement of sodium ions and electrochemical reactions, unlike conventional lithium ion batteries which are widely used.

[0048] Unlike lithium, a scarce resource with limited reserves, sodium dissolves in seawater and can be easily produced, making sodium-ion batteries superior to lithium-ion batteries in terms of cost.

[0049] In addition, since sodium ions are alkaline ions with an oxidation state of +1, just like lithium ions, their characteristics are similar, so it is expected that existing facilities can be utilized when manufacturing sodium-ion batteries.

[0050] However, sodium-ion batteries have a lower energy density than lithium-ion batteries. The oxidation / reduction potential of sodium (Na + -2.71 V ( / Na) is the oxidation / reduction potential of lithium (Li + Since it is higher than -3.04 V ( / Li), the operating voltage of sodium-ion batteries is lower than that of lithium-ion batteries, and as a result, they have a lower energy density.

[0051] Sodium-ion batteries are known to be inferior to lithium-ion batteries in terms of lifespan characteristics. This is because the size of sodium ions (1.02 Å) is larger than that of lithium ions (0.76 Å), so there is a difference in the change in crystal structure due to ion intercalation and deintercalation.

[0052] To address these issues, research is being conducted on various cathode active materials for sodium-ion batteries, such as layered transition metal oxides, polyanionic compounds, and Prussian blue compounds.

[0053] The above-mentioned positive electrode active material for a sodium ion battery may be capable of intercalation and deintercalation of sodium ions.

[0054] Sodium ion cathode active materials based on layered transition metal oxides are divided into octahedral O3 and orthorhombic P2. Layered transition metal oxide-based cathode active materials are known to have excellent rate capability and high energy density during high-speed charging and discharging due to having a two-dimensional ion diffusion pathway.

[0055] Polyanionic compounds include NASICON, olivine, pyrophosphate, mixed phosphate, fluorophosphate, fluorosulfate, bisulfate, etc.

[0056] Prussian blue compounds include metal-organic framework compounds that have a structure similar to Prussian blue, which is used as a dye.

[0057] Meanwhile, the composition of the generated cathode active material varies depending on the type of precursor material that reacts with the sodium-containing raw material.

[0058] Step (a) above is a step of preparing by mixing a sodium-containing raw material and a precursor material to form the positive electrode active material.

[0059] Here, the sodium-containing raw material may be at least one selected from the group consisting of sodium hydroxide, sodium carbonate, sodium nitrate, sodium nitrite, sodium sulfate, sodium sulfite, sodium phosphate, disodium hydrogen phosphite, sodium fluoride, and sodium acetate, but is not limited thereto.

[0060] The above-mentioned positive electrode active material is synthesized by reacting a sodium-containing raw material with a precursor material. The above-mentioned manufacturing method uses high-temperature heat treatment as a method to react the sodium-containing raw material and the precursor material.

[0061] Here, the precursor material may include at least one element selected from the group consisting of Ni, Fe, Mn, Co, Cr, Li, Sb, Cr, Cu, Ru, Sr, Ti, Mg, Zn, Zr, Nb, Sn, Sb, and V.

[0062] For example, when the above sodium-containing raw material and the above precursor material react, NaCrO2, NaMnO2, NaFeO2, Na 0.72 Cr 0.86 Sb 0.14 O2, NaLi 1 / 3 Mn 2 / 3 O2, Na 0.55 [Ni 0.1 Fe 0.1 Mn 0.8 ]O2, Na 0.66 Li 0.22 Ru 0.78 Layered transition metal oxides such as O2 or polyanionic compounds such as NaFePO4 can be synthesized.

[0063] Meanwhile, the precursor material can be prepared by reacting raw materials to prepare the mixture of step (a) above. For example, the precursor material can be prepared by reacting one or more raw materials containing the elements Ni, Fe, Mn, Co, Cr, Li, Sb, Cr, Cu, Ru, Sr, Ti, Mg, Zn, Zr, Nb, Sn, Sb, and V. The raw materials may be sulfates, carbonates, nitrates, acetates, silicates, phosphates, borates, hydrofluorics, chlorides, hydroxides, or oxides containing the aforementioned elements.

[0064] Next, step (b) above is a step of heat-treating the mixture to produce an anode active material.

[0065] In step (b) above, the mixture can be loaded into a refractory box with an internal space and then heat-treated.

[0066] A refractory box is a type of refractory container used to manufacture a desired product by firing precursor materials while preventing direct contact with flames, smoke, etc.

[0067] Therefore, as long as the shape of the above-mentioned refractory case is provided with a space to load a precursor material inside, it is not limited to prismatic, cylindrical, or elliptical shapes and can be used in various ways depending on the purpose.

[0068] Meanwhile, although the composition of the aforementioned positive electrode active material for a sodium ion battery varies depending on the type, it can be manufactured by calcining a mixture containing a sodium-containing raw material and a precursor material in common.

[0069] Here, sodium contained in raw materials such as NaOH and Na2CO3 introduced into the refractory box for the calcination of the precursor material can penetrate into the refractory box during the calcination process and react with Al2O3, SiO2, etc., which are the main components of the conventional refractory box.

[0070] Due to such sodium penetration and reaction, Na x -(Al / Si) y -O z By-products such as the back are formed.

[0071] In particular, sodium-containing raw materials are more alkaline than lithium-containing raw materials, so a byproduct layer is easily formed. This byproduct layer causes damage to the inner wall of the refractory, shortens the strength and lifespan of the refractory, and may reduce the number of repeated uses or even make a single firing process impossible.

[0072] To improve this, the possibility of by-product generation can be reduced by excluding Si-containing raw materials from the main components of the refractory casing, or by coating the inner wall of the refractory casing with spinel or the like, thereby reducing side reactions between the refractory casing and the sodium-containing raw materials.

[0073] However, if the content of Si-containing raw materials among the main components of the refractory armor is reduced, the content of Al-containing raw materials must be increased; in this case, there is a problem where the possibility of Al-derived by-products occurring instead of Si-derived by-products increases, and the overall strength of the refractory armor decreases as Si-containing raw materials among the main components are excluded or reduced.

[0074] Meanwhile, since the above refractory casing must be repeatedly exposed to a high-temperature firing process, it can be manufactured from a ceramic material with a high melting point.

[0075] Ceramic materials are materials composed of compounds formed by combining metal elements such as silicon (Si), aluminum (Al), titanium (Ti), zirconium (Zr), and magnesium (Mg) with nonmetal or metalloid elements such as oxygen, carbon, and nitrogen through high-temperature heat treatment.

[0076] For example, the ceramic material constituting the above refractory case is Al2O3, MgO, SiO2, K2O, ZrO, ZrO2, CaO, Fe x O y It may include various materials known as materials for constructing refractory armor, such as the back.

[0077] In addition to the chemical composition expressed by the aforementioned chemical formula, the properties of ceramic materials can vary depending on the form they form, that is, the type of mineral phase.

[0078] Examples of mineral phases of ceramic materials that can be used in the above refractory case include spinel, corundum, mullite, spodumene, zircon, quartz, petalite, eucryptite, sodium disilicate, sodium metasilicate, forsterite, magnesium metasilicate, alumina, silicate, etc.

[0079] The general forms of these materials are described as follows, but are not limited thereto. For example, the coefficient of thermal expansion of each component is an exemplary value measured in a temperature range of 25°C to 800°C.

[0080] Spinel is a mineral with an isometric crystal structure represented by MgO·Al2O3, and as measured in one example, it is 6.72 x 10⁻⁶. -6 It can have a coefficient of thermal expansion of / ℃.

[0081] Corundum is a hexagonal crystal mineral represented as Al2O3, and as measured in one example, it is 7.26X10 -6 It can have a coefficient of thermal expansion of / ℃.

[0082] Mullite is an orthorhombic mineral with a crystal structure represented as 3Al2O3·2SiO2, and as measured in one example, it is 5.84X10 -6 It can have a coefficient of thermal expansion of / ℃.

[0083] Spodumene is represented as Li2O·Al2O3·nSiO2 and is divided into monoclinic α-spodumene and tetragonal β-spodumene depending on the formation temperature, and as measured in one example, 0.44×10⁻⁶ -6 It can have a coefficient of thermal expansion of / ℃.

[0084] Zircon is a tetragonal crystalline phase represented as ZrO2·SiO2, and as measured in one example, it is 2.03X10 -6 It can have a coefficient of thermal expansion of / ℃.

[0085] Quartz is a hexagonal crystalline phase represented by SiO2, and as measured in one example, it is 7.64X10 -6 It can have a coefficient of thermal expansion of / ℃.

[0086] Meanwhile, most refractory materials used in the manufacture of positive electrode active materials for conventional lithium-ion batteries contain cordierite, mullite, and spinel as constituent components.

[0087] The above manufacturing method is an improvement based on the discovery that cordierite, among these components, readily reacts with sodium ions and deteriorates.

[0088] In other words, in conventional refractory casings containing cordierite, sodium penetrates and reacts with the refractory casing during the firing process, which can lead to problems such as the deterioration of the refractory casing's components, causing peeling or damage.

[0089] To minimize the manufacturing cost of the final fired product, refractory kilns must be reused; however, refractory kilns that have peeled off can degrade product performance, making reuse impossible or extremely difficult. Additionally, damaged refractory kilns cannot be used.

[0090] Cordierite is an orthorhombic mineral with a crystal structure represented by 2MgO·2Al2O3·5SiO2, and as measured in one example, 1.76X10 -6 It can have a coefficient of thermal expansion of / ℃.

[0091] When sodium ions react with cordierite, thermal images such as nepheline, sodium magnesium silicate, and sodium aluminum silicate can be formed.

[0092] Such thermal imaging can reduce the bonding strength between components and become a factor causing delamination of the refractory shell.

[0093] As the precursor material is fired using the above refractory casing, sodium from the sodium-containing raw material (NaOH, etc.) contained in the precursor material penetrates into the refractory casing, and Na is deposited on the inner side of the refractory casing. x -(Al / Si) y -O z It can deposit impurities expressed with a composition such as that.

[0094] For example, nepheline, represented as (Na,K)AlSiO4, is also called nephelite and is approximately 16 x 10⁻⁶ -6 It can have a coefficient of thermal expansion of / ℃.

[0095] As such, the byproduct formed by the reaction of sodium ions has a significantly higher coefficient of thermal expansion compared to other components constituting the refractory casing, which can cause deformation or breakage of the refractory casing.

[0096] Specifically, when using a refractory casing containing cordierite, an impurity layer (or deterioration layer) having a predetermined thickness may be formed on the inner side of the main body, particularly on the bottom surface.

[0097] Furthermore, cracks may occur in the generated impurity layer, causing the mixture loaded into the refractory box to penetrate or detach from the refractory box, making it impossible to manufacture the anode active material.

[0098] To improve these problems, the lifespan characteristics of the refractory casing can be improved by excluding cordierite from the components of the main body into which the precursor material is loaded, so that the reaction in which sodium among the sodium-containing raw materials (NaOH, etc.) included in the precursor material penetrates into the refractory casing and forms impurities can be suppressed.

[0099] Accordingly, the proportion of the cordierite phase in the above body may be less than 1 weight%, for example, less than 1 weight%, less than 0.5 weight%, less than 0.1 weight%, or 0%.

[0100] Meanwhile, the above main body may include at least one metal oxide selected from spinel, corundum, mullite, spodumene, zircon, quartz, petalite, eucryptite, lithium disilicate, lithium metasilicate, sodium disilicate, sodium metasilicate, forsterite, magnesium metasilicate, alumina, and silicate.

[0101] In particular, the main body may include the metal oxide as a main material. Here, including the metal oxide as a main material means that 45 weight percent or more of the components constituting the main body is a metal oxide, or that at least one of the weight ratio, molar ratio, and volume ratio of the component belonging to the metal oxide among the various compositions is the highest.

[0102] If a refractory casing is used as the main material of the above body, which contains the metal oxide but contains extremely little or no cordierite, side reactions during the firing of the loaded sodium-containing raw material can be suppressed.

[0103] Accordingly, the generation of by-products such as Na-(Al / Si)-O is reduced, thereby improving the durability of the refractory box and allowing the refractory box to be used in multiple firing processes, and furthermore, preventing product performance deterioration due to contamination of the firing result.

[0104] Meanwhile, the above main body may have a spinel content of 25 wt% or less, for example, 25 wt%, 24.5 wt%, 24 wt%, 23.5 wt%, 23 wt%, 22.5 wt%, 22 wt%, 21.5 wt%, 21 wt%, 20.5 wt%, 20 wt%, 19.5 wt%, 19 wt%, 18.5 wt%, 18 wt%, 17.5 wt%, 17 wt%, 16.5 wt%, 16 wt%, 15.5 wt%, 15 wt%, 14.5 wt%, 14 wt%, 13.5 wt%, 13 wt%, 12.5 wt%, 12 wt%, 11.5 wt%, 11 wt%, 10.5 wt%, 10 wt%, or a range between two of these values. there is.

[0105] The above body may not contain cordierite, which has a relatively low coefficient of thermal expansion, but instead may have a spinel content that satisfies the range described above.

[0106] In addition, the above-mentioned main body may have a corundum content of 15 wt% or more, for example, 15 wt%, 15.5 wt%, 16 wt%, 16.5 wt%, 17 wt%, 17.5 wt%, 18 wt%, 18.5 wt%, 19 wt%, 19.5 wt%, 20 wt%, 20.5 wt%, 21 wt%, 21.5 wt%, 22 wt%, 22.5 wt%, 23 wt%, 23.5 wt%, 24 wt%, 24.5 wt%, 25 wt%, or a range between two of these values.

[0107] The above main body may exclude cordierite, which has excellent heat resistance, and instead have a corundum content that satisfies the range described above.

[0108] Meanwhile, in the firing process of precursor materials using a refractory casing, in addition to peeling or deterioration caused by sodium penetration and reaction, cracking due to repeated thermal shock can also act as one of the factors determining the lifespan of the refractory casing.

[0109] For example, if the precursor material expands during firing, it applies pressure to the refractory casing, particularly the walls, which can cause cracks. Another example is that volume changes of individual components within the refractory casing body composition can act as a cause for cracks. In particular, if the composition constituting the refractory casing body reacts with sodium and transforms into a material with a high coefficient of thermal expansion, cracks can easily occur.

[0110] As a means to minimize the occurrence of such cracks, a sintered material containing petalite can be used as the refractory casing.

[0111] Specifically, the main body of the above-mentioned refractory case may include a spodumene phase sintered from a raw material including petalite, in particular β-spodumene.

[0112] In one example, the main body has a spodumene content of 45 wt% or more, for example, 45 wt%, 45.5 wt%, 46 wt%, 46.5 wt%, 47 wt%, 47.5 wt%, 48 wt%, 48.5 wt%, 49 wt%, 49.5 wt%, 50 wt%, 50.5 wt%, 51 wt%, 51.5 wt%, 52 wt%, 52.5 wt%, 53 wt%, 53.5 wt%, 54 wt%, 54.5 wt%, 55 wt%, 55.5 wt%, 56 wt%, 56.5 wt%, 57 wt%, 57.5 wt%, 58 wt%, 58.5 wt%, 59 wt%, 59.5 wt%, 60 wt%, or between two of these values. It can be a range.

[0113] The above main body contains a high content of spodumene, which has low reactivity to sodium ions, thereby suppressing side reactions during the calcination of the positive electrode active material for a sodium ion battery and minimizing the formation of a thermal phase. In addition, spodumene can suppress the thermal expansion of the refractory body.

[0114] Meanwhile, the spodumene phase formed from petalite can have a low volume expansion rate, unlike that formed from α-spodumene.

[0115] Specifically, petalite can be converted into a solid solution containing β-spodumene and SiO2 during the sintering process of the refractory casing.

[0116] Since these solid solutions have a low rate of volume change within the temperature range where the precursor material is fired, they can reduce the problem of cracks occurring in the refractory due to stress caused by volume changes.

[0117] Specifically, the spodumene phase derived from petalite has a volume change rate of 0.020% or less in the range of 25 to 1,200°C, whereas the structure derived from α-spodumene can have a volume change rate exceeding 0.1% in the range of 25 to 1,200°C.

[0118] In another example, the above body may be one in which discontinuous aggregate is dispersed within a continuous matrix of base material.

[0119] When firing the precursor material, components constituting the refractory shell with a small average particle size are used as the base material for the protective layer because they have high reactivity with sodium, while other components can be applied as aggregates with a relatively large average particle size.

[0120] If the above main body has the shape described above, fine parent material can be filled between aggregates with a large average particle size.

[0121] As a result, during the sintering of the refractory shell, the base material and aggregate can bond with each other or individually to form a dense structure.

[0122] This dense structure suppresses delamination caused by the penetration and reaction of sodium and provides excellent impact resistance, thereby preventing the refractory casing from breaking during the firing of the precursor material.

[0123] As an example of a protective layer composition capable of forming a dense structure, the average particle size of the base material is 0.5 to 25 μm and the average particle size of the aggregate is 150 to 900 μm, but is not limited thereto.

[0124] The method for manufacturing particles having such particle sizes is not limited, and, for example, depending on the type of raw material and the desired characteristics, methods such as evaporation-condensation, chemical vapor deposition, gas-phase pyrolysis, gas-phase reduction, coprecipitation, hydrolysis, spray drying, freeze-drying, pyrolysis, reduction, solid-state reaction, sublimation, and solution methods may be utilized.

[0125] In one example, a parent material with a small average particle size can be obtained by pulverizing the raw material through various grinding methods.

[0126] For example, raw materials can be ground using grinding methods such as ball mills, pebble mills, rod mills, roller mills, colloid mills, impact mills, and jet mills.

[0127] The above refractory casing is mainly used under high-temperature firing conditions. If the coefficient of thermal expansion of the ceramic material used as aggregate and base material is high, the rate of volume change before and after firing is excessively large, which can cause cracking of the refractory casing.

[0128] Accordingly, it is desirable that at least one of the aggregate and the base material constituting the refractory body, or at least one of the ceramic material used as the aggregate and the base material, has a relatively small coefficient of thermal expansion.

[0129] The thermal expansion coefficient of such base material or aggregate may vary depending on the composition of the above-mentioned refractory armor and the absolute magnitude of the thermal expansion coefficient.

[0130] For example, in one example of the present invention, a refractory shell can be formed using an aggregate whose coefficient of thermal expansion is relatively smaller than the coefficient of thermal expansion of the base material.

[0131] Since the aggregate exists as a discontinuous phase within a continuous matrix composed of the base material, if the coefficient of thermal expansion of the aggregate is high in this type of refractory casing, localized volume changes may occur in some areas of the refractory casing, thereby forming stress.

[0132] Generally, ceramic materials containing SiO2 in their crystal structure may have a lower coefficient of thermal expansion than ceramic materials that do not contain SiO2 in their crystal structure.

[0133] In such refractory containers, among the components excluding petalite, a ceramic material containing SiO2 in its crystal structure can be used as the aggregate.

[0134] In addition, in another example of the present invention, a refractory shell may be formed using a base material whose coefficient of thermal expansion is relatively smaller than that of the aggregate.

[0135] In such a refractory armor, the occurrence of cracks in the refractory armor can be reduced by using a base material with a small high-temperature volume change rate to alleviate stress concentration in the continuous phase matrix.

[0136] Meanwhile, the porosity of the above-mentioned main body may be 20 volume% or less, for example, 20 volume%, 17.5 volume%, 15 volume%, 12.5 volume%, 10 volume%, 7.5 volume%, 5 volume%, 2.5 volume%, or 1 volume% or less. However, the characteristics of the above-mentioned refractory case are not limited thereto.

[0137] One exemplary method for achieving such porosity is to densify the constituent components of the main body. In particular, if the porosity of the part that comes into direct contact with the sodium-containing raw material loaded in the refractory case is within the aforementioned range, the phenomenon of delamination caused by sodium penetration and / or reaction with the sodium-containing raw material can be further suppressed.

[0138] If the porosity of the above main body is reduced, the possibility of sodium originating from the sodium-containing raw material penetrating into the above refractory casing during heat treatment using the above refractory casing may also be reduced.

[0139] Meanwhile, the heat treatment of step (b) above is performed at a maximum temperature of 600 to 1,200°C, for example, 600°C, 625°C, 650°C, 675°C, 700°C, 725°C, 750°C, 775°C, 800°C, 825°C, 850°C, 875°C, 900°C, 925°C, 950°C, 975°C, 1000°C, 1025°C, 1050°C, 1075°C, 1100°C, 1125°C, 1150°C, 1175°C, 1200°C, or a temperature within a range between two of these values ​​for 6 to 18 hours, for example, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, It may be performed for 10 hours, 10.5 hours, 11 hours, 11.5 hours, 12 hours, 12.5 hours, 13 hours, 13.5 hours, 14 hours, 14.5 hours, 15 hours, 15.5 hours, 16 hours, 16.5 hours, 17 hours, 17.5 hours, 18 hours, or for a time between two of these values. Here, heat treatment may be performed in a kiln at a rate of 1 to 10°C per minute, for example, 1°C, 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C, 10°C, or between two of these values, followed by furnace cooling, but is not limited thereto.

[0140] Sodination by the sodium-containing raw material is performed at the aforementioned heat treatment temperature, and a positive electrode active material for a sodium ion battery can be synthesized.

[0141] Meanwhile, cordierite reacts with sodium at approximately 575°C to form a thermal image. Therefore, a refractory casing containing cordierite may form a thermal image and crack when heat treated at the highest temperature in the above range.

[0142] On the other hand, the refractory box used in the above manufacturing method does not contain cordierite or contains an extremely small amount, and can be used one or more times for the manufacture of the anode active material.

[0143] In one example, the positive active material prepared by the above method can be represented by the following chemical formula 1:

[0144] [Chemical Formula 1]

[0145] Na w M1 x M2 y M3 z O2

[0146] In the above formula, M1, M2, and M3 are each at least one selected from the group consisting of Ni, Fe, Mn, Co, Cr, Li, Sb, Cr, Cu, Ru, Sr, Ti, Mg, Zn, Zr, Nb, Sn, Sb, and V, and 0.5≤w≤1.5, 0≤x≤1, 0≤y≤1, 0≤z≤1, x+y+z=1.

[0148] Method for manufacturing a refractory case for firing precursor materials

[0149] According to another aspect of the present specification, a method for manufacturing a refractory box for firing a precursor material is provided, comprising: (i) preparing a molded body formed into a predetermined shape that includes a metal oxide as the main component and provides a space for loading a precursor material; and (ii) heat-treating the molded body at 1,100 to 1,400°C.

[0150] For metal oxides below, refer to the above.

[0151] Here, the forming of step (i) may utilize known methods used in the manufacture of refractory cases. For example, it may be formed into a shape with an internal space by applying pressure through a press.

[0152] The heat treatment of step (ii) above is a process for sintering the main body composition and can be performed at a high temperature of 1,100°C or higher, for example, 1,100°C, 1,150°C, 1,200°C, 1,250°C, 1,300°C, 1,350°C, 1,400°C, or in a range between two of these values.

[0153] This heat treatment is performed at 10 to 5,000℃ / hr, for example, 10℃ / hr, 25℃ / hr, 50℃ / hr, 75℃ / hr, 100℃ / hr, 125℃ / hr, 150℃ / hr, 200℃ / hr, 250℃ / hr, 300℃ / hr, 350℃ / hr, 400℃ / hr, 450℃ / hr, 500℃ / hr, 750℃ / hr, 1,000℃ / hr, 1,250℃ / hr, 1,500℃ / hr, 1,750℃ / hr, 2,000℃ / hr, 2,250℃ / hr, 2,500℃ / hr, 3,000℃ / hr, 3,500℃ / hr, 4,000℃ / hr, 4,500℃ / hr, The process may be carried out by increasing the temperature at a rate of 5,000°C / hr or a range between two of these values ​​and maintaining it for 1 to 24 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours, 24 hours, or a range between two of these values. When such high-temperature heat treatment is performed, the metal oxide may be converted into a dense body. The characteristics of the refractory casing containing the dense metal oxide are as described above. The heat treatment temperature, the rate of increase, and the holding time may vary depending on the characteristics of the main body composition constituting the refractory casing.

[0154] Here, if the heat treatment temperature of step (ii) is 1,100°C or higher and the main body composition has a specific composition, the densification of the metal oxide proceeds, thereby improving the life characteristics of the refractory casing.

[0156] The details described above will be explained in more detail below through examples. However, these examples are for illustrative purposes only and should not be interpreted as limiting the scope of this specification.

[0158] The following examples were performed under 25°C, atmospheric pressure, and an air atmosphere unless otherwise specified.

[0160] Comparative Examples and Examples

[0161] A refractory casing was manufactured by hydraulically press molding the raw material to have the composition of Table 1 below and then sintering it at 1,250°C.

[0162] division Spinel corundum Spodumin mulelite quartz Cordierlight zircon Comparative example 34.1 14.1 - 4.2 - 45.3 2.3 Examples 15.7 20.7 54.8 6.0 2.8 - -

[0163] (Unit: weight%)

[0165] Experimental Example

[0166] The reactivity between the refractory material and the sodium raw material used in the manufacture of cathode active materials for sodium-ion batteries was analyzed. Here, natrite (Na2CO3) was used as the sodium raw material.

[0167] After loading sodium raw material into the refractory casing prepared in the above comparative example and example, the temperature was raised to 800°C at a rate of 5°C per minute and fired for 1 hour, followed by furnace cooling.

[0168] The deterioration layer formed by the reaction of sodium raw material with the refractory casing of the comparative example was crushed and XRD analyzed, and the phase fraction is shown in Table 2 below.

[0169] division Spinel Cordierlight corundum zircon mulelite A1 B1 C1 D1 Comparative example 40.5 23.7 11.2 2.2 3.4 7.6 6.1 4.7 0.5 A1: Nepheline (Na 0.873 AlSiO4)B1: Sodium Magnesium Silicate (Na3MgAlSi2O8)C1: Sodium Aluminum Silicate (Na3MgAlSi2O8)C1: Sodium Aluminum Silicate (Na3MgAlSi2O8) 1.45 Al 1.45 Si 0.55 O4)D1: Periclase (MgO)

[0171] Components A1, B1, C1, and D1 are formed by the reaction of refractory material and natrite.

[0172] From the above results, it can be confirmed that the conventional refractory casing having the composition of the comparative example reacts with the sodium raw material to form a degradation layer during the manufacture of the positive electrode active material for a sodium ion battery. In particular, it can be confirmed that the cordierite contained in the refractory casing of the comparative example mainly reacts with natrite to form the degradation layer.

[0173] In addition, in the refractory case of the comparative example, cracks were formed due to a reaction between the refractory case and the sodium, and the sodium completely penetrated the lower surface of the refractory case through the cracks, making it unusable.

[0174] Meanwhile, the refractory box manufactured in the above example did not form a separate deterioration layer. Unlike the refractory box of the comparative example, no separate cracks occurred in the refractory box of the example and remained inside the crucible. After crushing the material remaining inside the refractory box, XRD analysis was performed, and the phase fractions are shown in Table 3 below.

[0175] division A2 B2 C2 D2 Examples 93.0 2.9 2.1 1.4 A2: Natrite (Na2CO3) B2: Sodium Magnesium Silicate (Na3MgAlSi2O8) C2: Corundum (Al2O3) D2: Akimotoite (MgSiO3)

[0177] In the refractory casing of the example, the sodium raw material did not react with the refractory casing, so no deterioration layer was formed, and it can be confirmed that the majority of the residual material maintained the natrite phase.

[0179] The refractory casings of the above comparative example and example, which underwent calcination of the sodium raw material, are shown in FIG. 1.

[0180] Referring to Fig. 1, in the refractory case of the comparative example, it can be seen that the natrite reacts with the refractory case to cause cracks, and the reactant has completely penetrated to the bottom surface.

[0181] On the other hand, in the refractory casing of the example, it can be confirmed that no deterioration layer is formed or cracks occur, and that natrite remains on the bottom surface inside the crucible and forms a separate layer.

[0183] Although embodiments of this specification have been described above, those skilled in the art may modify and change this specification in various ways by adding, changing, deleting, or adding components, etc., without departing from the spirit of this specification as described in the claims, and such modifications and changes shall also be deemed to be included within the scope of the rights of this specification.

Claims

Claim 1 A refractory casing for firing a positive electrode active material for a sodium ion battery, comprising a main body having a space for loading a precursor material, wherein the main body comprises spinel, corundum, and spodumene, the spinel content of the main body is 25% by weight or less, and the cordierite content of the main body is less than 1% by weight. Claim 2 In claim 1, the main body is a refractory casing for firing a positive electrode active material for a sodium ion battery, which is non-reactive with a sodium-containing raw material at 800°C. Claim 3 A refractory casing for firing a positive electrode active material for a sodium ion battery, wherein the sodium-containing raw material is at least one selected from the group consisting of sodium hydroxide, sodium carbonate, sodium nitrate, sodium nitrite, sodium sulfate, sodium sulfite, sodium phosphate, disodium hydrogen phosphite, sodium fluoride, and sodium acetate. Claim 4 A refractory casing for firing a positive electrode active material for a sodium ion battery, wherein the main body further comprises at least one metal oxide selected from mullite, zircon, quartz, petalite, eucryptite, lithium disilicate, lithium metasilicate, sodium disilicate, sodium metasilicate, forsterite, magnesium metasilicate, alumina, and silicate. Claim 5 In claim 1, the main body is a refractory casing for firing a positive electrode active material for a sodium ion battery, having a corundum content of 15 weight% or more. Claim 6 In claim 1, the main body is a refractory box for firing a positive electrode active material for a sodium ion battery, having a spodumene content of 45% by weight or more. Claim 7 A refractory box for firing a positive electrode active material for a sodium ion battery, wherein the porosity of the main body is 20 volume% or less in the first paragraph. Claim 8 A refractory casing for firing positive active material for a sodium ion battery, wherein the main body is a discontinuous aggregate dispersed in a continuous matrix of base material. Claim 9 A refractory casing for firing a positive electrode active material for a sodium ion battery, wherein, in claim 8, the average particle size of the base material is 0.5 to 25 μm and the average particle size of the aggregate is 150 to 900 μm.

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