Positive electrode composition for sodium secondary battery, with multifunctional surface deterioration prevention additive added thereto, positive electrode for sodium secondary battery and sodium secondary battery including same, method for manufacturing positive electrode composition for sodium secondary battery, with multifunctional surface deterioration prevention additive added thereto, and method for manufacturing slurry including same

Abstract

The present invention relates to a positive electrode composition for sodium secondary batteries, in which a multifunctional additive for preventing surface degradation is incorporated. The composition comprises a positive electrode active material including a sodium transition-metal oxide, and an organic framework, and contains at least one functional group capable of binding to transition-metal atoms.

Description

A positive electrode composition for a sodium secondary battery with a multifunctional surface degradation prevention additive added thereto, a positive electrode for a sodium secondary battery and a sodium secondary battery comprising the same, a method for producing a positive electrode composition for a sodium secondary battery with a multifunctional surface degradation prevention additive added thereto, and a method for producing a slurry comprising the same

[0001] The present invention relates to a positive electrode composition for a sodium secondary battery in which surface deterioration is prevented by adding a multifunctional surface deterioration prevention additive.

[0002] Sodium secondary batteries are being actively researched as an alternative to lithium secondary batteries. Compared to lithium secondary batteries, sodium secondary batteries offer the advantages of being environmentally friendly, price-competitive, and possessing superior energy storage properties.

[0003] Sodium secondary batteries, like lithium secondary batteries, generate electrical energy by utilizing the oxidation and reduction reactions that occur when sodium ions are inserted and removed from the positive and negative electrodes.

[0004] Therefore, materials capable of insertion and extraction of sodium ions are used as the positive and negative electrodes, and the positive electrode material in particular plays an important role in determining the capacity and performance of the battery.

[0005] One approach to improving the capacity and performance of sodium secondary batteries involves designing the cathode active material to include a sodium transition metal oxide, including nickel (Ni). Nickel significantly increases battery capacity by increasing the number of sodium ions that can enter the sodium layer in the sodium transition metal oxide. Nickel also offers the advantages of low production costs and environmental friendliness.

[0006] Meanwhile, if the passage of sodium ions on the surface of the positive electrode material is blocked, the output of the battery decreases.

[0007] Additionally, if a phase transformation occurs in the sodium transition metal oxide located on the surface of the cathode active material, cracks easily form in the cathode active material particles, and the transition metal dissolves through the cracks. The dissolution of the transition metal reduces the capacity efficiency of the battery.

[0008] In addition, hydrofluoric acid (HF) generated by electrochemical decomposition of the electrolyte corrodes metal materials such as battery containers and current collectors, and causes transition metals to be dissolved through cracks that occur on the surface of positive electrode active material particles.

[0009] In particular, layered sodium transition metal oxides used in sodium secondary batteries undergo phase transformation continuously to maintain bonds between transition metal atoms and oxygen ions within the lattice structure, as sodium ions significantly change the volume of the lattice during the insertion and deintercalation process.

[0010] In this process, an irreversible phase is created, which significantly reduces the cycle life of the cathode material and greatly weakens the durability of the battery.

[0011] Coating and doping methods have been introduced in the past as methods to prevent such surface deterioration phenomena, but they have limitations in that they cannot avoid surface deterioration due to phase transformation and corrosion, and the process is complicated.

[0012] Therefore, the development of a method that effectively solves the surface deterioration and structural instability problems of sodium transition metal oxide-based cathode active materials and is easy to apply to industry is a major task for the industry.

[0013] In order to solve the above-described problems of the present invention, the present invention provides a sodium secondary battery positive electrode composition having a multifunctional surface degradation prevention additive that is easy to apply to industry while effectively suppressing the surface degradation problem and structural instability problem of a sodium transition metal oxide-based positive electrode active material, a sodium secondary battery positive electrode comprising the same, and a sodium secondary battery.

[0014] Another object of the present invention is to provide a positive electrode composition for a sodium secondary battery to which the aforementioned multifunctional surface degradation prevention additive is applied, and a method for producing a slurry containing the same.

[0015] In order to solve the above-described problem, the present invention provides a positive electrode composition for a sodium secondary battery with a multifunctional surface degradation prevention additive, comprising a positive electrode active material including a sodium transition metal oxide and an organic skeleton, and including an additive including at least one functional group capable of bonding with a transition metal atom, wherein the additive can bind to a transition metal atom present on the surface of the positive electrode active material and suppress the transition metal atom from moving within the sodium transition metal oxide lattice.

[0016] In one embodiment of the present invention, the functional group can be combined with a transition metal atom through a condensation reaction.

[0017] In one embodiment of the present invention, the organic skeleton is sp 2 May contain carbon.

[0018] In one embodiment of the present invention, the organic skeleton may include unshared electrons.

[0019] In one embodiment of the present invention, the positive electrode active material may include at least one of the positive electrode active materials represented by the following chemical formula 1.

[0020] [Chemical Formula 1]

[0021] Na x TMO2

[0022] In the above chemical formula 1, TM may be one or more elements selected from Ni, Fe, Mn, and Cu. In the above chemical formula 1, 0.7≤x≤1 may be satisfied.

[0023] In one embodiment of the present invention, the organic skeleton includes a porphyrin-based organic substance, and the functional group may include at least one selected from the group consisting of a hydroxyl group (-OH), a carboxyl group (-COOH), a sulfonic acid group (-SO3H), and a combination thereof.

[0024] In one embodiment of the present invention, the additive may include one or more of the compounds represented by the following chemical formulas 2 to 13.

[0025] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0026] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 2] [Chemical Formula 3]

[0027] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0028] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 4] [Chemical Formula 5]

[0029] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0030] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 6] [Chemical Formula 7]

[0031] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0032] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 8] [Chemical Formula 9]

[0033] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0034] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 10] [Chemical Formula 11]

[0035] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0036] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 12] [Chemical Formula 13]

[0037] In one embodiment of the present invention, the additive may be added in an amount of 1 wt% or less relative to the positive electrode active material.

[0038] Another embodiment of the present invention for solving the above-described problem may be a sodium secondary battery positive electrode including a sodium secondary battery positive electrode composition to which a multifunctional surface deterioration prevention additive is added, and a sodium secondary battery including the same.

[0039] Another embodiment of the present invention for solving the above-described problem is a method for manufacturing a positive electrode composition for a sodium secondary battery with a multifunctional surface degradation prevention additive, the method comprising the steps of mixing a positive electrode active material including a sodium transition metal oxide and an additive in an organic solvent environment, performing centrifugal separation, and drying in a vacuum oven, wherein the additive may include at least one functional group capable of bonding with an organic skeleton and a transition metal atom.

[0040] In one embodiment of the present invention, the mixing step may be performed at 10°C to 80°C.

[0041] Another embodiment of the present invention for solving the above-described problem is a method for producing a positive electrode slurry for a sodium secondary battery with a multifunctional surface degradation prevention additive, comprising the steps of preparing a positive electrode composition comprising a positive electrode active material including a sodium transition metal oxide and an additive, and mixing the positive electrode composition with a conductive material, a binder, and a solvent to produce a slurry, wherein the additive may include at least one functional group capable of bonding to an organic skeleton and a transition metal atom.

[0042] In one embodiment of the present invention, the step of preparing the positive electrode composition may include the step of mixing the positive electrode active material including the sodium transition metal oxide and the additive in an organic solvent environment, the step of performing centrifugal separation, and the step of drying in a vacuum oven.

[0043] In one embodiment of the present invention, the step of preparing the positive electrode composition may include the step of preparing a positive electrode active material powder including a sodium transition metal oxide and the step of mixing the positive electrode active material powder with an additive.

[0044] In one embodiment of the present invention, the mixing step may be performed at 5°C to 80°C.

[0045] The present invention has the advantage that, according to the above-described configuration and bonding relationship, the transition metal is fixed within the lattice, thereby suppressing the displacement of the transition metal and the resulting phase transformation, and effectively suppressing surface deterioration.

[0046] In addition, it has the advantage of forming a stable CEI (cathode electrolyte interphase) around the cathode active material, thereby suppressing the formation of cracks in the cathode active material and preventing the elution of transition metals.

[0047] Additionally, it has the advantage of preventing a decrease in battery capacity efficiency by capturing corrosive hydrofluoric acid (HF) and preventing corrosion caused by HF and the elution of transition metals.

[0048] In addition, the multifunctional surface deterioration prevention additive disclosed in the present invention can be expected to have a surface deterioration prevention effect even when simply added to a sodium transition metal oxide-based cathode active material, and thus has the advantage of being very easy to apply to industry.

[0049] In addition, the multifunctional surface deterioration prevention additive disclosed in the present invention can prevent surface deterioration even in a small amount, and is also inexpensive, so it has an economical advantage.

[0050] In addition, the multifunctional surface degradation prevention additive disclosed in the present invention can be mixed with a sodium transition metal oxide-based cathode active material through a room temperature process to exhibit an effect, so it is easy to apply in various stages of lithium secondary battery manufacturing, and has an economical advantage in terms of process cost.

[0051] FIG. 1 is a drawing showing the movement of sodium ions at the interface between a sodium transition metal oxide-based cathode active material and an electrolyte during charging and discharging of a sodium secondary battery, and the appearance of an additive disclosed in one embodiment of the present invention being combined with the cathode active material.

[0052] FIG. 2 illustrates an embodiment of an additive disclosed in the present invention in which the additive is bonded to the periphery of a cathode active material including a transition metal, and distinguishes the properties of the functional group and the organic skeleton in the additive.

[0053] FIG. 3 is a flowchart of a method for manufacturing a positive electrode composition for a sodium secondary battery with a multifunctional surface degradation prevention additive added according to one embodiment of the present invention.

[0054] FIG. 4 is a flowchart of a method for manufacturing a positive electrode slurry for a sodium secondary battery with a multifunctional surface degradation prevention additive added according to one embodiment of the present invention.

[0055] FIG. 5 is a flowchart showing one embodiment of detailed steps of the step of preparing the bipolar composition in FIG. 4.

[0056] FIG. 6 is a flowchart showing another embodiment of the detailed steps of the step of preparing the bipolar composition in FIG. 4.

[0057] Figure 7 shows the results of measuring the life characteristics of a sodium secondary battery manufactured including comparative group 1 and experimental group 1.

[0058] Figure 8 shows the results of measuring the life characteristics of a sodium secondary battery for comparative group 1 and experimental group 2.

[0059] Figure 9 shows the results of measuring the life characteristics of a sodium secondary battery for comparative group 1 and experimental group 3.

[0060] This specification clarifies the scope of the present invention and explains the principles of the present invention and discloses embodiments thereof to enable those skilled in the art to practice the invention. The disclosed embodiments may be implemented in various forms.

[0061] It should be understood that terms such as “include,” “may include,” or “have,” which may be used in various embodiments of the present invention, are intended to indicate the presence of a feature described in the specification (e.g., a function, a number, a step, an operation, a component, a part, or a combination thereof), and do not preclude the possibility of the presence or addition of one or more other features.

[0062] As used herein, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0063] When a component is referred to as being “connected, coupled” to another component, it should be understood that the component may be directly connected or coupled to the other component, but that there may also be a new component between the component and the other component. Conversely, when a component is referred to as being “directly connected” or “directly coupled” to another component, it should be understood that no new component exists between the component and the other component.

[0064] The terms "first," "second," etc., used herein may be used to describe various components, but the components should not be limited by the terms. The terms are used solely to distinguish one component from another.

[0065] Hereinafter, a preferred embodiment of a positive electrode composition for a sodium secondary battery to which a multifunctional surface degradation prevention additive is added according to one embodiment of the present invention will be described in detail.

[0066] First, the present invention relates to a positive electrode composition for a sodium secondary battery to which a multifunctional surface deterioration prevention agent is added, and which comprises a positive electrode active material including a sodium transition metal oxide and an additive.

[0067] The additive disclosed in the present invention can prevent surface deterioration of the positive electrode active material simply by adding it to the positive electrode active material and mixing it, and has the advantage of not requiring high-temperature heat treatment or a special synthesis method.

[0068] Below, we will examine each configuration in detail.

[0069] <Cathode active material>

[0070] Here, the cathode active material is a cathode active material that can be used in a sodium ion secondary battery, and may be a sodium transition metal oxide-based cathode active material containing a high content of transition metal.

[0071] In one embodiment, the cathode active material including a sodium transition metal oxide may include at least one cathode active material represented by the following chemical formula 1.

[0072] [Chemical Formula 1]

[0073] Na x TMO2

[0074] In the above chemical formula 1, TM may be one or more elements selected from Ni, Fe, Mn, and Cu. In the above chemical formula 1, 0.7≤x≤1 may be satisfied.

[0075] For example, the above chemical formula 1 is NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2(NFM111), NaNi 0.5 Fe 0.25 Mn 0.25 O2(NFM211), NaNi 0.25 Fe 0.5 Mn 0.25 O2(NFM121) or NaNi 0.25 Fe 0.25 Mn 0.5 It could be O2(NFM112).

[0076] Additionally, the cathode active material may include a material that can be conventionally coated or doped on a sodium transition metal oxide-based cathode active material, without being limited thereto.

[0077] Additives

[0078] In one embodiment of the present invention, the additive may be a material including a functional group capable of bonding to a transition metal atom in an organic skeleton.

[0079] FIG. 1 is a drawing showing the movement of sodium ions at the interface between a sodium transition metal oxide-based cathode active material and an electrolyte during charging and discharging of a sodium secondary battery, and the appearance of an additive disclosed in one embodiment of the present invention being combined with the cathode active material.

[0080] Referring to Figure 1, insertion and extraction of sodium ions occur at the surface of the positive electrode active material forming an interface with the electrolyte.

[0081] During this process, a phenomenon of site migration may occur in which sodium ions are removed from the sodium transition metal oxide lattice and the vacant spaces are occupied by transition metals.

[0082] When cation mixing occurs, transition metal ions block the migration paths through which sodium ions are inserted and removed, thereby reducing the output of sodium secondary batteries. Furthermore, the migration of transition metal ions within the lattice causes phase transformation of the sodium transition metal oxide, destabilizing the lattice.

[0083] This cation mixing phenomenon is the main cause of surface deterioration of sodium transition metal oxide cathode active materials.

[0084] The additive disclosed in the present invention is a material including a functional group capable of bonding with a transition metal atom, and as illustrated in FIG. 1, can form a bond with a transition metal atom within a sodium transition metal oxide lattice on the surface of a positive electrode active material.

[0085] Accordingly, the mobility of transition metal atoms is restricted, fixing their positions within the sodium transition metal oxide lattice. By restricting the mobility of transition metals, the aforementioned site migration phenomenon of transition metal ions is suppressed, thereby preventing surface deterioration of the cathode active material and reducing output of the sodium secondary battery.

[0086] Specifically, the additive disclosed in the present invention may be a substance containing at least one functional group capable of bonding with a transition metal atom through a condensation reaction.

[0087] Additionally, each functional group may form a bond with one or two transition metal atoms within the cathode active material lattice.

[0088] For example, the functional group may include at least one selected from the group consisting of a hydroxyl group (-OH), a carboxyl group (-COOH), a sulfonic acid group (-SO3H), and combinations thereof, and the hydroxyl group, the carboxyl group, and the sulfonic acid group may each form a bond with one to two transition metal atoms within the positive electrode active material lattice. Preferably, the functional group may include at least one carboxyl group (-COOH).

[0089] Additionally, in one embodiment of the present invention, the additive may include at least two functional groups, either homologous or heterologous, in the organic skeleton, and each of the two or more functional groups included in the additive may form a bond with one or two transition metal atoms within the cathode active material lattice.

[0090] For example, the additive may contain two or more carboxyl groups (-COOH), in which case each carboxyl group may form bonds with up to two transition metal atoms, such that the additive as a whole may form bonds with four or more transition metal atoms by the two or more carboxyl groups.

[0091] Accordingly, transition metal atoms within the cathode active material lattice can be more effectively fixed with a small amount of additive, and surface deterioration of the cathode active material can be more effectively prevented.

[0092] At this time, two or more functional groups included in the organic skeleton may be selected from the group consisting of a hydroxyl group (-OH), a carboxyl group (-COOH), a sulfonic acid group (-SO3H), and a combination thereof.

[0093] Next, in one embodiment of the present invention, the additive has an organic skeleton, and the organic skeleton is sp 2 May contain carbon.

[0094] FIG. 2 illustrates the appearance of an additive disclosed in one embodiment of the present invention being bonded to the periphery of a transition metal oxide-based cathode active material and the properties of the functional group and organic skeleton in the additive.

[0095] Referring to Figure 2, the additive is sp 2 Because it contains carbon, it is stable in organic electrolytes and has sodium affinity. In addition, the aforementioned functional group forms a bond with transition metals, showing transition metal affinity.

[0096] Therefore, when the additive is added to the cathode active material, the functional group faces the cathode active material and the organic skeleton faces the electrolyte, and the additive can surround the cathode active material in a micelle structure without any special conditions or treatments.

[0097] Also, the sp of the additive that surrounds the positive electrode active material 2 Carbon, due to its affinity for sodium, facilitates the formation of a cathode electrolyte interphase (CEI) around the cathode active material and stabilizes the formed CEI. This suppresses cracking in the cathode active material particles and prevents the dissolution of transition metals through cracks, thereby preventing a decline in the capacity and lifespan of sodium secondary batteries.

[0098] Next, in one embodiment of the present invention, an additive disclosed has an organic skeleton, and the organic skeleton may include unshared electrons. Preferably, the organic skeleton may include electron donor nitrogen.

[0099] Unpaired electrons can capture hydrofluoric acid (HF), which is generated by the electrochemical decomposition of the organic electrolyte during long-term battery operation. Hydrofluoric acid is a corrosive substance that corrodes metallic materials such as the battery container and current collector, and causes transition metals to leach through cracks that form on the surface of the cathode active material particles.

[0100] Therefore, the additive can suppress corrosion by retaining hydrofluoric acid by including unshared electrons, prevent transition metals from being eluted from the cathode active material, and improve the long-term operation stability of sodium secondary batteries.

[0101] As an example of an organic skeleton having the aforementioned characteristics, the additive disclosed in the present invention may include a porphyrin-based organic material as the organic skeleton.

[0102] In addition, as an example of an additive disclosed in the present invention having an organic skeleton and functional group having the above-described characteristics, it may include one or more of the compounds represented by the following chemical formulas 2 to 13. Preferably, it may be Tetrakis(4-carboxyphenyl)porphyrin.

[0103] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0104] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 2] [Chemical Formula 3]

[0105] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0106] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 4] [Chemical Formula 5]

[0107] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0108] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 6] [Chemical Formula 7]

[0109] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0110] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 8] [Chemical Formula 9]

[0111] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0112] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 10] [Chemical Formula 11]

[0113] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0114] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 12] [Chemical Formula 13]

[0115] In one embodiment of the present invention, the additive may be added in an amount of 1 wt% or less relative to the positive electrode active material.

[0116] That is, the additive disclosed in one embodiment of the present invention has an advantage of effectively binding to a cathode active material even in a small amount due to a functional group having a transition metal affinity and an organic skeleton having a sodium affinity, inhibiting movement of transition metal atoms within the lattice, effectively wrapping the cathode active material to stably form and maintain a cathode electrolyte interphase (CEI), and also inhibiting corrosion of hydrofluoric acid (HF), thereby effectively preventing surface deterioration of the cathode active material even in a very small amount of 1 wt% or less compared to the cathode active material.

[0117] Next, according to another embodiment of the present invention, a positive electrode for a sodium secondary battery and a sodium secondary battery including a positive electrode composition for a sodium secondary battery to which the multifunctional surface degradation prevention additive is added can be provided.

[0118] The positive electrode for a sodium secondary battery disclosed in this example and the sodium secondary battery including the same also include a positive electrode composition for a sodium secondary battery to which a multifunctional surface deterioration prevention additive is added, and show excellent characteristics in terms of capacity, output, and lifespan, which will be described in detail through experimental examples described below.

[0119] Next, with reference to FIG. 3, a method for manufacturing a positive electrode composition for a sodium secondary battery with a multifunctional surface degradation prevention additive added, which is another embodiment of the present invention, will be described.

[0120] FIG. 3 is a flowchart of a method for manufacturing a positive electrode composition for a sodium secondary battery with a multifunctional surface degradation prevention additive added according to one embodiment of the present invention.

[0121] A method for manufacturing a positive electrode composition for a sodium secondary battery with a multifunctional surface degradation prevention additive added according to one embodiment disclosed in the present invention may include a step of mixing a positive electrode active material and an additive in an organic solvent environment (S100), a step of performing centrifugal separation (S200), a washing step (not shown), and a step of drying in a vacuum oven (S300).

[0122] The step of mixing the positive electrode active material and the additive in an organic solvent environment (S100) is a step of introducing the positive electrode active material and the additive containing the sodium transition metal oxide into an organic solvent and mixing them.

[0123] Specifically, the cathode active material including a sodium transition metal oxide may include at least one cathode active material represented by the following chemical formula 1, similar to the above-described example.

[0124] [Chemical Formula 1]

[0125] Na x TMO2

[0126] In the above chemical formula 1, TM may be one or more elements selected from Ni, Fe, Mn, and Cu. In the above chemical formula 1, 0.7≤x≤1 may be satisfied.

[0127] Additionally, the cathode active material may include a material that can be conventionally coated or doped on a sodium transition metal oxide-based cathode active material, without being limited thereto.

[0128] Next, the additive may be a material containing a functional group capable of bonding with a transition metal atom in the organic skeleton, similar to the aforementioned embodiment. Accordingly, the additive may form a bond with a transition metal atom within the sodium transition metal oxide lattice on the surface of the positive electrode active material.

[0129] Specifically, the additive disclosed in the present invention may be a substance containing at least one functional group capable of bonding with a transition metal atom through a condensation reaction.

[0130] Additionally, each functional group may form a bond with one or two transition metal atoms within the cathode active material lattice.

[0131] For example, the functional group may include at least one selected from the group consisting of a hydroxyl group (-OH), a carboxyl group (-COOH), a sulfonic acid group (-SO3H), and combinations thereof, and the hydroxyl group, the carboxyl group, and the sulfonic acid group may each form a bond with one to two transition metal atoms within the positive electrode active material lattice. Preferably, the functional group may include at least one carboxyl group (-COOH).

[0132] Additionally, in one embodiment of the present invention, the additive may include at least two functional groups, either homologous or heterologous, in the organic skeleton, and each of the two or more functional groups included in the additive may form a bond with one or two transition metal atoms within the cathode active material lattice.

[0133] Accordingly, transition metal atoms within the cathode active material lattice can be more effectively fixed with a small amount of additive, and surface deterioration of the cathode active material can be more effectively prevented.

[0134] At this time, two or more functional groups included in the organic skeleton may be selected from the group consisting of a hydroxyl group (-OH), a carboxyl group (-COOH), a sulfonic acid group (-SO3H), and a combination thereof.

[0135] Additionally, the additive has an organic skeleton, and the organic skeleton is sp 2 May contain carbon.

[0136] Additionally, the additive has an organic skeleton, and the organic skeleton may include unpaired electrons. Preferably, the organic skeleton may include electron donor nitrogen.

[0137] An example of an additive having the aforementioned properties may include a porphyrin-based organic material as the organic skeleton.

[0138] For example, the additive may include one or more of the compounds represented by the following chemical formulae 2 to 13. Preferably, it may be Tetrakis(4-carboxyphenyl)porphyrin.

[0139] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0140] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 2] [Chemical Formula 3]

[0141] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0142] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 4] [Chemical Formula 5]

[0143] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0144] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 6] [Chemical Formula 7]

[0145] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0146] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 8] [Chemical Formula 9]

[0147] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0148] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 10] [Chemical Formula 11]

[0149] [Correction pursuant to Rule 91, September 12, 2025][Deleted]

[0150] [Correction pursuant to Rule 91, September 12, 2025] [Chemical Formula 12] [Chemical Formula 13]

[0151] At this time, the additive may be added in an amount of 1 wt% or less relative to the positive electrode active material.

[0152] That is, the additive disclosed in one embodiment of the present invention has an advantage of effectively binding to a cathode active material even in a small amount due to a functional group having a transition metal affinity and an organic skeleton having a sodium affinity, inhibiting movement of transition metal atoms within the lattice, effectively wrapping the cathode active material to stably form and maintain a cathode electrolyte interphase (CEI), and also inhibiting corrosion of hydrofluoric acid (HF), thereby effectively preventing surface deterioration of the cathode active material even in a very small amount of 1 wt% or less compared to the cathode active material.

[0153] Next, the solvent into which the positive electrode active material and additives are added may be an organic solvent.

[0154] An example of an organic solvent may include, but is not limited to, ethanol.

[0155] Next, the method of mixing the cathode active material and additive in an organic solvent environment may be magnetic stirring, but is not limited thereto.

[0156] In particular, the process of mixing the positive electrode active material and additives in an organic solvent environment can be performed at room temperature.

[0157] Specifically, the room temperature may be 0°C to 100°C. Alternatively, it may be 10°C to 100°C. Alternatively, it may be 0°C to 80°C. Preferably, it may be 10°C to 80°C. More preferably, it may be 20°C to 50°C.

[0158] The step of performing centrifugal separation (S200) is performed after mixing the positive electrode active material and the additive in an organic solvent environment by magnetic stirring, etc., and is intended to obtain only the positive electrode active material (or positive electrode composition) to which the additive is combined.

[0159] The washing step is performed to wash the obtained positive electrode composition (or positive electrode active material combined with an additive), and the drying step (S300) in an oven can be performed to remove moisture or organic solvent remaining in the positive electrode composition.

[0160] Next, with reference to FIGS. 3 to 6, a method for manufacturing a positive electrode slurry for a sodium secondary battery with a multifunctional surface degradation prevention additive added, which is another embodiment of the present invention, will be described.

[0161] FIG. 3 is a flow chart of a method for manufacturing a positive electrode composition for a sodium secondary battery with a multifunctional surface degradation prevention additive added thereto according to one embodiment of the present invention. FIG. 4 is a flow chart of a method for manufacturing a positive electrode slurry for a sodium secondary battery with a multifunctional surface degradation prevention additive added thereto according to one embodiment of the present invention. FIG. 5 is a flow chart showing one embodiment of detailed steps of the step of preparing the positive electrode composition in FIG. 4. FIG. 6 is a flow chart showing another embodiment of detailed steps of the step of preparing the positive electrode composition in FIG. 4.

[0162] Referring to FIG. 4, a method for manufacturing a positive electrode slurry for a sodium secondary battery with a multifunctional surface degradation prevention additive added according to one embodiment disclosed in the present invention may include a step of preparing a positive electrode composition (S1000) and a step of manufacturing a slurry (S2000).

[0163] The step of preparing the bipolar composition (S1000) can be divided into three methods again.

[0164] Looking at the first method for preparing a positive electrode composition, it can be prepared according to the method for manufacturing a positive electrode composition for a sodium secondary battery with the aforementioned multifunctional surface degradation prevention additive added.

[0165] Specifically, as illustrated in FIG. 3, it may include a step of mixing a positive electrode active material and an additive in an organic solvent environment (S100), a step of performing centrifugal separation (S200), a washing step, and a step of drying in an oven (S300).

[0166] At this time, the details of the positive electrode active material, additive, organic solvent, and performing method can be interpreted in the same manner as described in the above-mentioned example (e.g., method for producing positive electrode slurry for sodium secondary battery with multifunctional surface deterioration prevention additive added), and duplicate descriptions will be omitted.

[0167] Referring to FIG. 5, a second method for preparing a positive electrode composition may include a step of preparing positive electrode active material powder (S1110) and a step of mixing positive electrode active material powder and an additive (S1120).

[0168] This is a method of simply mixing positive electrode active material powder and additives and adding them during slurry production.

[0169] Simple mixing can be understood as mixing the positive electrode active material and additives in powder form in a container and shaking them, or stirring them with a hand or a stick, without any special device (e.g., a stirring device, a ball milling device, etc.) or special conditions (e.g., heating, pressurized conditions, or solvent conditions, etc.).

[0170] In addition, this method simplifies the manufacturing process of a cathode slurry for a sodium secondary battery and has an economic advantage because it does not require special equipment or special conditions that were required in existing coating methods, milling methods, doping methods, etc.

[0171] At this time, the detailed properties and examples of the cathode active material and additives used are the same as in the above-described examples, and duplicate descriptions will be omitted.

[0172] Referring to FIG. 6, a third method for preparing a positive electrode composition may include a step (S1210) of preparing positive electrode active material powder and additives.

[0173] This method involves preparing cathode active material powder and additives and introducing them into the slurry manufacturing step described below. Strictly speaking, unlike the first and second methods described above, the cathode composition in this method, which combines the additive and cathode active material, is formed during the mixing process introduced into the slurry manufacturing step.

[0174] In addition, the additive disclosed in the present invention can be understood as a method that can be attempted in that it is expected to have an effect of preventing deterioration of the surface of the positive electrode active material even with a content of 1 wt% or less compared to the positive electrode active material.

[0175] The detailed properties and examples of the cathode active material and additives used are the same as in the examples described above, and duplicate descriptions will be omitted.

[0176] The next step for preparing a slurry is to prepare a slurry by adding and mixing the positive electrode composition, conductive material, binder, and solvent prepared in the previous step.

[0177] Specifically, the conductive material is not particularly limited as long as it is a conventionally known conductive material that has conductivity without maintaining chemical changes in the anode composition.

[0178] For example, conductive materials of the carbon black series such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black, conductive materials of the conductive fiber series such as carbon fiber or metal fiber, conductive materials of the metal powder series such as fluorocarbon, aluminum, and nickel powder, conductive materials of the conductive metal oxide series such as titanium oxide, and conductive materials of the polyphenylene derivative series can be used.

[0179] Next, the binder is not particularly limited as long as it is a conventionally known binder that can perform the role of holding the positive electrode active material and the conductive material.

[0180] For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), and polyamideimide (PAI) can be used.

[0181] Next, a solvent for preparing a slurry may be a conventionally known solvent such as N-methyl-2-pyrrolidone (NMP), polypyrrolidone, isopropanol, petroleum ether, tetrahydrofuran, ethyl acetate, N,N-dimethylacetamide, N,N-dimethylformamide, n-hexane, and halogenated hydrocarbons.

[0182] Hereinafter, the contents and results of an experiment performed on a sodium secondary battery positive electrode composition with a multifunctional surface degradation prevention additive added thereto, manufactured including a method for manufacturing a sodium secondary battery positive electrode composition with a multifunctional surface degradation prevention additive added thereto according to one embodiment of the present invention, and a sodium secondary battery manufactured including the same will be examined.

[0183] Experimental Example 1

[0184] 1. Experimental method

[0185] a) (Comparative group 1 - NFM111) NFM111 (NaNi) was synthesized by a conventional method. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2) was manufactured to prepare control group 1.

[0186] b) (Experimental group 1 - TCPP / NFM111) Dissolve tetrakis(4-carboxyphenyl)porphyrin (hereinafter referred to as “TCPP”) in ethanol solvent using a magnetic stirrer to create a solution.

[0187] NFM111 cathode material manufactured using the same synthetic method as the comparative group 1 was added to the prepared solution and magnetic stirring was performed for 12 hours.

[0188] Afterwards, wash with ethanol through a centrifuge and dry in a vacuum oven to prepare experimental group 1.

[0189] c) The positive electrode active material of the above comparative group 1 and the positive electrode composition of the experimental group 1 are dissolved in an NMP solvent at a weight ratio of (positive electrode active material or positive electrode composition): conductive agent: binder = 96:2:2, and applied onto aluminum foil to manufacture a positive electrode.

[0190] d) Confirm the life characteristics (or cycle characteristics) of the manufactured sodium secondary battery including comparative group 1 and experimental group 1.

[0191] The cycle characteristics were measured and compared for two cycles at 0.1C and then at 0.5C based on 1C (C-rate) = 150 mA / g in the voltage range of 2.2 V - 4.0 V.

[0192] 2. Experimental Results

[0193] Figure 7 shows the results of measuring the life characteristics of a sodium secondary battery manufactured including comparative group 1 and experimental group 1.

[0194] Referring to Fig. 7, the discharge capacity retention rate of experimental group 1 after 200 cycles was approximately 78.57% (approximately 140 mAh·g -1 About 110mAh·g -1 ) showed a decrease in comparison group 1 (46.15%, approximately 130 mAh·g) -1 About 60mAh·g -1 It was confirmed that the lifespan characteristics were improved by 32.42% compared to the previous results.

[0195] <Experimental Example 2> - Validation Experiment of the Positive Slurry Manufacturing Method

[0196] 1. Experimental method

[0197] a) A cathode slurry for a sodium secondary battery with the aforementioned multifunctional surface degradation prevention additive was prepared using various manufacturing methods, and sodium secondary batteries manufactured including the cathode slurry were prepared as experimental groups 2 and 3. A sodium secondary battery manufactured using a conventional method (comparative group 1) was prepared as a comparative group. This experiment was conducted to confirm the effectiveness of a cathode slurry manufacturing method according to an embodiment of the present invention by comparing the life characteristics of comparative group 1 and experimental groups 2 and 3.

[0198] b) The manufacturing method of (Experimental Group 2 - TCPP / NFM111) is as follows:

[0199] - NFM111 (NaNi) cathode active material was synthesized using a conventional synthesis method. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2) is manufactured and prepared in powder form.

[0200] - Prepare TCPP with additives

[0201] - Prepare the positive electrode composition by mixing NFM111 powder and TCPP in a container and stirring using a test rod.

[0202] - The cathode composition (NFM111 + TCPP), conductive agent, and binder are mixed in a weight ratio of “cathode composition: conductive agent: binder = 96:2:2” to prepare cathode slurry.

[0203] - The manufactured slurry is applied onto aluminum foil to manufacture a positive electrode, and combined with a sodium-metal negative electrode to form a battery.

[0204] c) The manufacturing method of (Experimental Group 3 - TCPP / NFM111) is as follows:

[0205] - NFM111 (NaNi) cathode active material was synthesized using a conventional synthesis method. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2) is manufactured and prepared in powder form.

[0206] - Prepare TCPP with additives

[0207] - Before preparing the slurry, NFM111 powder and TCPP are mixed together with the conductive agent and binder to form “(NFM111+TCPP): conductive agent: binder = 96 wt%: 2 wt%: 2 wt%” and then mixed to prepare the cathode slurry.

[0208] - The manufactured slurry is applied onto aluminum foil to manufacture a positive electrode, and combined with a sodium-metal negative electrode to form a battery.

[0209] d) Cycle characteristics were measured for control group 1 and experimental group 2. Cycle characteristics were measured and compared for two cycles of 0.1C and then 0.5C, based on 1C = 150mA / g in the voltage range of 2.2V - 4.0V.

[0210] 2. Experimental results

[0211] a) Figure 8 shows the results of measuring the life characteristics of a sodium secondary battery for comparative group 1 and experimental group 2. Figure 9 shows the results of measuring the life characteristics of a sodium secondary battery for comparative group 1 and experimental group 3.

[0212] b) Referring to Figure 8, the discharge capacity retention rate of experimental group 2 after 150 cycles was approximately 78.57% (140 mA / g -> 110 mA / g), confirming a 28.57% improved life characteristic compared to comparative group 1 (approximately 50%, 140 mA / g -> 70 mA / g).

[0213] c) Referring to FIG. 9, the discharge capacity retention rate of experimental group 3 after 150 cycles was approximately 82.14% (140 mA / g -> 115 mA / g), confirming a 28.29% improved life characteristic compared to comparative group 1 (approximately 53.85%, 130 mA / g -> 70 mA / g).

[0214] d) These results can be interpreted to indicate that in all three methods of manufacturing positive electrode slurry disclosed in the present invention, the additive effectively combines with the positive electrode active material and can prevent surface deterioration of the positive electrode active material.

[0215] The foregoing description of the present invention is provided for illustrative purposes only. Those skilled in the art will readily appreciate that modifications to other specific embodiments can be made without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting.

[0216] For example, although the present invention has been described with reference to an embodiment illustrated in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and variations of the embodiments are possible from this.

[0217] Therefore, the true technical protection scope of the present invention is indicated by the technical idea of ​​the patent claims described below, and all changes or modified forms derived from the image and scope of the patent claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims

1. A cathode active material comprising a sodium transition metal oxide; and An additive having an organic skeleton and including at least one functional group capable of bonding to a transition metal atom, The above additives are, A positive electrode composition for a sodium secondary battery, to which a multifunctional surface degradation prevention additive is added, characterized in that the functional group binds to a transition metal atom present on the surface of the positive electrode active material and inhibits the movement of the transition metal atom within the sodium transition metal oxide lattice.

2. In paragraph 1, The above functional group is, A positive electrode composition for a sodium secondary battery, comprising a multifunctional surface degradation prevention additive characterized by bonding with a transition metal atom through a condensation reaction.

3. In paragraph 2, The above organic skeleton is sp 2 A positive electrode composition for a sodium secondary battery, characterized in that it contains carbon and has a multifunctional surface degradation prevention additive added thereto.

4. In paragraph 2 or 3, A positive electrode composition for a sodium secondary battery, characterized in that the organic skeleton includes a non-covalent electron, and a multifunctional surface degradation prevention additive is added.

5. In paragraph 2, A sodium secondary battery cathode composition with a multifunctional surface deterioration prevention additive, characterized in that the cathode active material comprises at least one cathode active material represented by the following chemical formula 1: [Chemical Formula 1] Na x TMO2 In the above chemical formula 1, TM may be one or more elements selected from Ni, Fe, Mn, and Cu. In the above chemical formula 1, 0.7≤x≤1 may be satisfied.

6. In paragraph 4, The above organic skeleton includes a porphyrin-based organic substance, A positive electrode composition for a sodium secondary battery with a multifunctional surface deterioration prevention additive added, characterized in that the functional group includes at least one selected from the group consisting of a hydroxyl group (-OH), a carboxyl group (-COOH), a sulfonic acid group (-SO3H), and combinations thereof.

7. [Revised on 12.09.2025 by Article 91 of the Rules] In paragraph 4, the additive is characterized in that it includes at least one of the compounds represented by the following chemical formulas 2 to 13, wherein a positive electrode composition for a sodium secondary battery with a multifunctional surface deterioration prevention additive is added: [Chemical Formula 2] [Chemical Formula 3] [Chemical Formula 4] [Chemical Formula 5] [Chemical Formula 6] [Chemical Formula 7] [Chemical Formula 8] [Chemical Formula 9] [Chemical Formula 10] [Chemical Formula 11] [Chemical Formula 12] [Chemical Formula 13] 8. In paragraph 1, A positive electrode composition for a sodium secondary battery, characterized in that the additive is added in an amount of 1 wt% or less relative to the positive electrode active material, and to which a multifunctional surface deterioration prevention additive is added.

9. A positive electrode for a sodium secondary battery, comprising a positive electrode composition for a sodium secondary battery to which a multifunctional surface deterioration prevention additive according to Article 1 is added.

10. A sodium secondary battery comprising a positive electrode for a sodium secondary battery according to Article 9.

11. A step of mixing a cathode active material including a sodium transition metal oxide and an additive in an organic solvent environment; a step of performing centrifugation; and Includes a drying step in an oven, The above additives are, organic skeleton; and A method for producing a positive electrode composition for a sodium secondary battery, wherein a multifunctional surface degradation prevention additive is added, characterized in that it contains at least one functional group capable of bonding with a transition metal atom.

12. In paragraph 11, The above mixing step is, A method for producing a positive electrode composition for a sodium secondary battery, characterized in that the positive electrode composition is prepared by adding a multifunctional surface degradation prevention additive, and is performed at a temperature of 10°C to 80°C.

13. In paragraph 11, The above functional group is, A method for producing a positive electrode composition for a sodium secondary battery, wherein a multifunctional surface deterioration prevention additive is added, characterized in that it combines with a transition metal atom through a condensation reaction.

14. In paragraph 13, The above organic skeleton is sp 2 A method for producing a positive electrode composition for a sodium secondary battery, wherein a multifunctional surface degradation prevention additive is added, characterized in that it contains carbon.

15. In paragraph 13 or 14, A method for producing a positive electrode composition for a sodium secondary battery, wherein the organic skeleton includes a non-covalent electron and a multifunctional surface degradation prevention additive is added.

16. In paragraph 13, A method for manufacturing a positive electrode composition for a sodium secondary battery with a multifunctional surface deterioration prevention additive, characterized in that the positive electrode active material comprises at least one of the positive electrode active materials represented by the following chemical formula 1: [Chemical Formula 1] Na x TMO2 In the above chemical formula 1, TM may be one or more elements selected from Ni, Fe, Mn, and Cu. In the above chemical formula 1, 0.7≤x≤1 may be satisfied.

17. In paragraph 15, The above organic skeleton includes a porphyrin-based organic substance, A method for producing a positive electrode composition for a sodium secondary battery with a multifunctional surface deterioration prevention additive added, characterized in that the functional group includes at least one selected from the group consisting of a hydroxyl group (-OH), a carboxyl group (-COOH), a sulfonic acid group (-SO3H), and combinations thereof.

18. [Revised on 12.09.2025 by Article 91 of the Rules] A method for manufacturing a positive electrode composition for a sodium secondary battery with a multifunctional surface deterioration prevention additive added, characterized in that the additive comprises at least one of the compounds represented by the following chemical formulas 2 to 13: [Chemical Formula 2] [Chemical Formula 3] [Chemical Formula 4] [Chemical Formula 5] [Chemical Formula 6] [Chemical Formula 7] [Chemical Formula 8] [Chemical Formula 9] [Chemical Formula 10] [Chemical Formula 11] [Chemical Formula 12] [Chemical Formula 13] 19. A step of preparing a cathode composition comprising a cathode active material including a sodium transition metal oxide and an additive; It comprises a step of preparing a slurry by mixing the above positive electrode composition with a conductive material, a binder, and a solvent, The above additives are, organic skeleton; and A method for producing a positive electrode slurry for a sodium secondary battery, wherein a multifunctional surface degradation prevention additive is added, characterized in that it contains at least one functional group capable of bonding with a transition metal atom.

20. In paragraph 19, The step of preparing the above bipolar composition is: A step of mixing the positive electrode active material including the sodium transition metal oxide and the additive in an organic solvent environment; a step of performing centrifugation; and A method for producing a positive electrode slurry for a sodium secondary battery, wherein a multifunctional surface degradation prevention additive is added, characterized in that the method comprises a step of drying in an oven.

21. In paragraph 19, The step of preparing the above bipolar composition is: A step of preparing a positive electrode active material powder containing a sodium transition metal oxide; and A method for producing a cathode slurry for a sodium secondary battery, characterized in that it comprises a step of mixing the cathode active material powder and an additive, and to which a multifunctional surface deterioration prevention additive is added.

22. In paragraph 20, The above mixing step is, A method for producing a positive electrode slurry for a sodium secondary battery, characterized in that the positive electrode slurry is prepared by adding a multifunctional surface degradation prevention additive, and is performed at a temperature of 5°C to 80°C.

23. In paragraph 19, The above functional group is, A method for producing a positive electrode slurry for a sodium secondary battery, wherein a multifunctional surface degradation prevention additive is added, characterized in that it combines with a transition metal atom through a condensation reaction.

24. In paragraph 23, The above organic skeleton is sp 2 A method for producing a positive electrode slurry for a sodium secondary battery, wherein a multifunctional surface degradation prevention additive is added, characterized in that it contains carbon.

25. In paragraph 23 or 24, A method for producing a positive electrode slurry for a sodium secondary battery, wherein the organic skeleton includes a non-covalent electron and a multifunctional surface degradation prevention additive is added.

26. In paragraph 23, A method for manufacturing a cathode slurry for a sodium secondary battery with a multifunctional surface deterioration prevention additive, characterized in that the cathode active material comprises at least one type of cathode active material represented by the following chemical formula 1: [Chemical Formula 1] Na x TMO2 In the above chemical formula 1, TM may be one or more elements selected from Ni, Fe, Mn, and Cu. In the above chemical formula 1, 0.7≤x≤1 may be satisfied.

27. In paragraph 25, The above organic skeleton includes a porphyrin-based organic substance, A method for producing a positive electrode slurry for a sodium secondary battery with a multifunctional surface deterioration prevention additive added, characterized in that the functional group includes at least one selected from the group consisting of a hydroxyl group (-OH), a carboxyl group (-COOH), a sulfonic acid group (-SO3H), and a combination thereof.

28. [Correction pursuant to Rule 91 12.

09. [2025] In the 25th paragraph, the additive is characterized in that it includes at least one compound represented by the following chemical formulas 2 to 13, a method for manufacturing a positive electrode slurry for a sodium secondary battery with a multifunctional surface deterioration prevention additive added: [Chemical Formula 2] [Chemical Formula 3] [Chemical Formula 4] [Chemical Formula 5] [Chemical Formula 6] [Chemical Formula 7] [Chemical Formula 8] [Chemical Formula 9] [Chemical Formula 10] [Chemical Formula 11] [Chemical Formula 12] [Chemical Formula 13]

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