A cathode material for a battery and a method for preparing the same

Abstract

The invention relates to a material for a battery cathode. The material is represented by NaxMyAzDtO2, where M is at least one metal selected from the group containing titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn); A is at least one metal selected from the group containing titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn); D is at least one metal selected from the group containing titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn); with 0.85 < x < 1.1, 0.1 < y < 0.9, 0.1 < z < 0.9, 0.1 < t < 0.9, and the material having a BET surface area in the range of 2.5 to 3.5 mA2 / g.

Description

[0001] DESCRIPTION

[0002] A CATHODE MATERIAL FOR A BATTERY AND A METHOD FOR PREPARING THE SAME

[0003] TECHNICAL FIELD

[0004] The present invention relates to electrodes and, for example, to the use of such electrodes in sodium-ion battery applications.

[0005] PRIOR ART

[0006] In the technical field, sodium-ion batteries exhibit many similarities to lithium-ion batteries, which are commonly used today. Both are rechargeable secondary batteries comprising an anode (negative electrode), a cathode (positive electrode), and an electrolyte. They store energy in the chemical bonds of the cathode and offer a compact energy storage solution. The charging and discharging processes in both battery types occur via a similar reaction mechanism. During charging, Na<+> (or Li<+>) ions detach from the cathode and migrate toward the anode, while electrons travel from the cathode through the external circuit (including the charger) to the anode to balance the charge. During discharge, this flow reverses: electrons travel back from the anode to the cathode, and Na<+> (or Li<+>) ions return to the cathode.

[0007] Layered metal oxide sodium-ion battery cathode materials offer advantages such as high volumetric energy density and easy synthesis. Among these, O3-type materials have the benefits of high specific capacity and stable performance. These materials constitute an important class of layered metal oxide sodium-ion battery cathode materials. However, O3-type materials are difficult to use because their surface is highly alkaline and not stable in air.

[0008] EP2828912B1 relates to metal-structure electrodes. EP2828912B1 discloses electrodes containing active materials of the formula AaMbXxOy, where A is one or more alkali metals selected from lithium, sodium, and potassium; M is one or more transition metals and / or one or more non-transition metals and / or one or more metalloids; X includes one or more atoms selected from niobium, antimony, tellurium, tantalum, bismuth, and selenium; and additionally 0 < a s 6; the range for b is 0 < b s 4; the range for x is 0 < x s 1 ; and y ranges from 2 s y < 1 o. Such electrodes are useful, for instance, in sodium and / or lithium-ion battery applications. BRIEF DESCRIPTION OF THE INVENTION

[0009] The objective of the invention is to prepare a cathode material for a battery that exhibits a high energy density.

[0010] In order to achieve the mentioned objective, the invention concerns a material for a battery cathode. The material is represented by NaxMyAzDtO2; M is at least one metal selected from the group containing titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn); A is at least one metal selected from the group containing titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn); D is at least one metal selected from the group containing titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn); and the material satisfies 0.85 < x < 1.1 , 0.1 < y < 0.9, 0.1 < z < 0.9, 0.1 < t < 0.9, and further has a BET surface area in the range of 2.5 to 3.5 mA2 / g. In this way, a larger active surface area on the electrode material is provided, increasing ion exchange and electrochemical reactions. Moreover, the material’s surface area increases capacity per unit weight, thereby enhancing the battery’s energy density.

[0011] In a preferred embodiment of the invention, the metal M in the material is nickel. By using nickel, the cathode material attains high energy density, and additionally, nickel-based cathode materials have a long cycle life. Furthermore, nickel ensures electrochemical stability at high voltages.

[0012] In another preferred embodiment of the invention, the metal A in the material is iron. Consequently, the presence of iron makes the cathode more thermally stable, reducing the risk of overheating.

[0013] In yet another preferred embodiment of the invention, the metal D in the material is manganese. Through the use of manganese, manganese ions enable fast diffusion within the cathode material, thereby providing high charge / discharge capacity.

[0014] In a further preferred embodiment, the Dv50 particle volume distribution of the material is in the range of 2.3 to 2.7 pm. This distribution indicates that particles are concentrated within a certain size range, reflecting high homogeneity of the material. This feature facilitates electrode fabrication and further enhances the electrochemical performance and durability of the material. Preferably keeping Dv50 below 20 pm ensures that the path for sodium ions and electrons within the cathode active material remains short, thus boosting the ion and electron conductivity of the cathode active material. Consequently, electrochemical kinetic performance and rate performance during charging and discharging are improved. Moreover, batteries using this cathode active material exhibit less positive electrode (cathode) polarization, improving capacity retention during charge and discharge cycling.

[0015] A battery containing a cathode material according to a preferred embodiment of the invention.

[0016] In a preferred application of the invention, the method comprises, preparing a solution of transition metal sulfates in predetermined stoichiometric ratios, stirring the solution, precipitating the stirred solution to obtain a powder, washing the obtained powder and drying it at a predetermined temperature, mixing the dried powder with sodium carbonate to obtain an intermediate product, and calcining the intermediate product in air. This method allows for the production of the material used as the cathode in an electrode.

[0017] In a preferred application of the invention, the solution is stirred at a temperature range of 70- 80°C. This temperature range is necessary for forming the desired size, morphology, and crystal structure of the synthesized cathode active material.

[0018] In a further preferred application of the invention, the solution is stirred for a duration of 2-4 hours. This duration meets the time requirement to complete the precipitation reaction.

[0019] In another preferred application of the invention, the dried powder is mixed at a 2:1 mol ratio with sodium carbonate. The reason for adding sodium carbonate in an amount greater than the targeted stoichiometric value is to compensate for the sodium loss that volatilizes during calcination.

[0020] In yet another preferred application of the invention, the intermediate product is calcined in the temperature range of 800-900°C. This calcination step incorporates sodium into the crystal structure and breaks down the oxalate-based framework obtained in the initial phase of the reaction, oxidizing it.

[0021] In a further preferred application of the invention, the intermediate product is calcined for at least 13 hours. This duration ensures that the calcination process reaches completion. DETAILED DESCRIPTION OF THE INVENTION

[0022] In this detailed description, the development forming the subject matter of the invention is explained with references to examples merely for better illustration, without any limitation implied.

[0023] The material for a battery cathode according to the invention has the formulation NaxMyAzDtO2. In this formulation:

[0024] • M, provided in the formula, is at least one metal selected from the group containing titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn) — in particular, nickel is chosen;

[0025] • A is at least one metal selected from the group containing titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn) — in particular, iron is chosen;

[0026] • D is at least one metal selected from the group containing titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn) — in particular, manganese is chosen.

[0027] For the sodium component, represented by x, the range is 0.85 < x < 1 .1 . For M, denoted byy, the range is 0.1 < y < 0.9. For A, denoted by z, the range is 0.1 < z < 0.9. For D, denoted by t, the range is 0.1 < t < 0.9. The resulting NaxMyAzDtO2 material has a BET surface area in the range of 2.5 to 3.5 mA2 / g.

[0028] A cathode material specifically developed for use in batteries, particularly sodium-ion batteries, is employed. In the method of preparing the cathode material, to synthesize (Ni1 / 3Fe1 / 3Mn1 / 3)C2O4, the starting reactants NiSO4-6H2O, FeSO4-7H2O, MnSO4-H2O, and Na2C2O4 are used alongside a co-precipitation agent. A solution comprising the appropriate stoichiometric ratios of transition metal sulfates is added to a solution containing sodium oxalate, which is being stirred, to form a mixture. To obtain the sodium oxalate solution, 5 grams of Na2C2O4 are weighed and dissolved in 100 ml of water. This is then placed into a reaction flask. While Na2C2O4 is stirring at a constant temperature of 70°C and a stirring rate of 2.5 rpm, in a separate beaker, 3.37 grams of FeSO4-7H2O, 3.15 grams of NiSO4-6H2O, and 2.03 grams of MnSO4-H2O are weighed. One adds 100 ml of pure water, places a stir bar, and dissolves them on a magnetic stirrer. Without applying heat, the substances dissolved in 100 ml pure water are transferred into the reaction flask, and then stirred for 3 hours at 70°C to obtain the solution. When this solution of reactants and the co-precipitation agent is added into the sodium oxalate solution, the temperature of the resulting mixture is continuously maintained at 70-80°C, especially at 70°C. Under atmospheric conditions, stirring is continued for 3 hours to perform the precipitation process. After the precipitation, the obtained powder is filtered and washed with pure water (with a purity / resistance of 18.2 MQ-cm). The washed powder is dried in air at 105°C. Next, the dried (Ni1 / 3Fe1 / 3Mn1 / 3)C2O4 powder is mixed with sodium carbonate at a 2:1 mol ratio. The mixture is calcined in air at 850°C for 16 hours. As a result of the calcination, Na[Ni1 / 3Fe1 / 3Mn1 / 3]O2 is obtained. In the experiment, the BET surface area of the material was measured to be 3 mA2 / g.

[0029] From the measurement results, the particle sizes were determined as follows:

[0030] • D(v, 0.1 ): 1.64378 pm

[0031] • D(v,0.5): 2.55959 pm

[0032] • D(v,0.9): 3.85744 pm

[0033] The notation “D(v,x)” indicates the diameter of particles that constitute x% of the total volume. For example, “D(v,0.1 )” represents the diameter of the particles comprising 10% of the total volume. Smaller particle sizes provide a large surface area, accelerating ion exchange and thereby improving the battery’s charge and discharge rates. Additionally, particles with smaller diameters increase electron and ion conductivity within the electrode, reducing internal resistance and thus enhancing energy efficiency. A uniform particle size distribution improves cycle stability, as more homogeneous sizes lead to less stress and cracking during cycling.

[0034] When the battery performance of the electrode material was measured, it was found that the Specific Capacitance after the first discharge cycle was 127 mAh / g at 0.1 C, and that the Coulombic Efficiency at 25°C was 99%.

[0035] As another example, using a sol-gel preparation method, Na0.75Fe0.25Cu0.25Mn0.502 with an 03 crystal structure was obtained as a cathode material. When the battery performance of this cathode material was measured, the Specific Capacitance after the first discharge cycle was determined to be 100 mAh / g at 0.1 C.

Claims

CLAIMS1. A material for a battery cathode wherein material is represented by NaxMyAzDtO2, where M is at least one metal selected from the group containing titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn); A is at least one metal selected from the group containing titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn); D is at least one metal selected from the group containing titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn); and 0.85 < x < 1 .1 , 0.1 < y < 0.9, 0.1 < z < 0.9, 0.1 < t < 0.9, and the material having a BET surface area in the range of 2.5 to 3.5 mA2 / g.

2. A material according to Claim 1 , wherein the metal M has nickel.

3. A material according to any of the preceding claims, wherein the metal A has iron.

4. A material according to any of the preceding claims, wherein the metal D has manganese.

5. A material according to any of the preceding claims, wherein the Dv50 particle volume distribution is in the range of 2.3 to 2.7 pm.

6. A battery containing a cathode material according to any of the preceding claims.

7. A method of preparing a cathode material according to any of the preceding claims, characterized by comprising the process steps of preparing a solution composed of transition metal sulfates in predetermined stoichiometric ratios, stirring the solution, precipitating the stirred solution to obtain a powder, washing and drying the obtained powder at a predetermined temperature, mixing the dried powder with sodium carbonate to obtain an intermediate product, and calcining the intermediate product in an air atmosphere.

8. A preparation method according to Claim 7, wherein the solution is stirred at a temperature range of 70-80°C.

9. A preparation method according to Claims 7-8, wherein the solution is stirred for 2-4 hours.

10. A preparation method according to Claim 7, wherein the dried powder is mixed with sodium carbonate at a 2:1 mol ratio.

11. A preparation method according to Claim 7, wherein the intermediate product is calcined in a temperature range of 800-900°C.

12. A preparation method according to Claim 7, wherein the intermediate product is calcined for at least 13 hours.