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KR-20260067061-A - Dopant Screening Method of Layered Transition Metal Oxide with Multiple Phase and Apparatus Therewith

KR20260067061AKR 20260067061 AKR20260067061 AKR 20260067061AKR-20260067061-A

Abstract

The present invention relates to a method for selecting a dopant effective in suppressing a phase transition of a layered transition metal oxide having multiple phases, and to an apparatus used in such a method, comprising: a first step of extracting a first phase and a second phase, which are multiple single-phase structures of the transition metal oxide, from a material database; a second step of deriving a multi-phase layered transition metal oxide structure in which the extracted multiple single phases, the first phase and the second phase, are stacked; a third step of deriving a structure doped with a dopant for the derived multi-phase layered transition metal oxide structure; a fourth step of calculating the difference in energy values before and after the phase transition of the first phase and the difference in energy values before and after the phase transition of the second phase for the multi-phase layered transition metal oxide structures before and after doping derived in the second and third steps; and a fifth step of repeating the third and fourth steps multiple times while varying the type of dopant. and, after the above-mentioned fifth step, a sixth step of selecting the dopant having the smallest difference in energy values before and after the phase transition for each of the first and second phases obtained; thereby, based on the structural and physical property information of a single-phase layered transition metal oxide, the structure and information of a multi-phase layered transition metal oxide are generated, and then the physical properties before and after the phase transition are calculated, so that a dopant capable of effectively suppressing the phase transition can be accurately and quickly selected.

Inventors

  • 민경민
  • 박태현

Assignees

  • 숭실대학교산학협력단

Dates

Publication Date
20260512
Application Date
20241105

Claims (12)

  1. A screening method for dopants capable of suppressing the phase transition of layered transition metal oxides (LTMOs), A first step of extracting a first phase and a second phase, which are multiple single-phase structures of a transition metal oxide, from a material database; A second step of deriving a multiphase layered transition metal oxide structure in which a plurality of extracted single phases, a first phase and a second phase, are stacked; A third step of deriving a dopant-doped structure for the derived multiphase layered transition metal oxide structure; A fourth step of calculating the difference in energy values before and after the phase transition of the first phase and the difference in energy values before and after the phase transition of the second phase for the multiphase layered transition metal oxide structure before and after doping derived in the second and third steps above; A fifth step of repeating the third and fourth steps multiple times while changing the type of dopant; and A screening method for dopants capable of suppressing phase transitions in layered transition metal oxides (LTMOs), comprising: a sixth step of selecting the dopant having the smallest difference in energy values before and after phase transition for each of the first and second phases obtained after the fifth step above.
  2. In paragraph 1, A screening method for dopants capable of suppressing phase transition of layered transition metal oxides (LTMOs), characterized in that, in the sixth step above, the dopant with the smallest change in lattice constant and volume change, along with the difference in energy values before and after the phase transition.
  3. In paragraph 1, In the third step above, the structure of the layered transition metal oxide doped with a dopant is derived such that at least a plurality of structures with different positions of the dopant are derived, A screening method for dopants capable of suppressing phase transition of layered transition metal oxides (LTMOs), characterized in that the energy value of the fourth step above is the average value of the structures of a plurality of doped layered transition metal oxides.
  4. In paragraph 1, A screening method for dopants capable of suppressing phase transition of layered transition metal oxides (LTMOs), characterized in that the above material database is an open database such as C2DB, JARVIS-DFT, Material Project (MP), or 2D Materials Encyclopedia (2DMatPedia).
  5. In paragraph 1 The above layered transition metal oxides (LTMOs) are NaFeO2 , and A screening method for a dopant capable of suppressing a phase transition of layered transition metal oxides (LTMOs), characterized in that the first phase is a P2 phase of Na₂Fe₂O₄ and the second phase is an O3 phase of Na₃Fe₃O₆ .
  6. In paragraph 5, The layered transition metal oxide structure in which the P2 phase and O3 phase are stacked is, The unit cell structure of P2 is positioned perpendicular to the unit cell structure of O3, and Depending on the chemical composition ratio of the matrix structure of the layered transition metal oxides (LTMOs) under analysis, the unit cell structure is expanded, while some of the iron (Fe) ions within the lattice structure are replaced by manganese (Mn) ions and some of the sodium (Na) ions are removed, and A screening method for a dopant capable of suppressing the phase transition of layered transition metal oxides (LTMOs), characterized by being P2/O3-Na 0.85 Fe 0.5 Mn 0.5 O 2 stabilized through density functional theory (DFT) calculations.
  7. In an apparatus for screening dopants capable of suppressing the phase transition of layered transition metal oxides (LTMOs), A material database (material DB) storing the single-phase structures of transition metal oxides; A first processor that derives a layered transition metal oxide structure in which the first and second phases are stacked by stacking a single phase, the first phase, and the second phase selected from the above material database; A second processor that derives a doped layered transition metal oxide structure by doping a dopant into the derived layered transition metal oxide structure; A third processor that calculates the difference in energy values before and after the phase transition of the first phase and the difference in energy values before and after the phase transition of the second phase for the layered transition metal oxide structure before and after doping derived from the first processor and the second processor; A memory for storing results obtained by repeatedly performing operations of the second processor and the third processor by changing the type of dopant; and A screening apparatus for dopants capable of suppressing phase transition of layered transition metal oxides (LTMOs), comprising: a controller for selecting, among the results stored in the memory, the dopant having the smallest difference in energy values before and after the phase transition of each of the first and second phases.
  8. In Paragraph 7, The above controller is a screening device for dopants capable of suppressing the phase transition of layered transition metal oxides (LTMOs), characterized by selecting the dopant with the smallest change in lattice constant and volume change, along with the difference in energy values before and after the phase transition.
  9. In Paragraph 7, The second processor above derives the structure of at least a plurality of doped layered transition metal oxides having different dopant positions, and A screening device for dopants capable of suppressing phase transition of layered transition metal oxides (LTMOs), characterized in that the energy value calculated in the third processor above is the average value of the structure of a plurality of doped layered transition metal oxides.
  10. In Paragraph 7, A screening apparatus for dopants capable of suppressing phase transition of layered transition metal oxides (LTMOs), characterized in that the above material database is an open database such as C2DB, JARVIS-DFT, Material Project (MP), or 2D Materials Encyclopedia (2DMatPedia).
  11. In Paragraph 7, The above layered transition metal oxides (LTMOs) are NaFeO2 , and A screening apparatus for a dopant capable of suppressing a phase transition of layered transition metal oxides (LTMOs), characterized in that the first phase is a P2 phase of Na₂Fe₂O₄ and the second phase is an O3 phase of Na₃Fe₃O₆ .
  12. In Paragraph 11, The layered transition metal oxide structure in which the P2 phase and O3 phase are stacked is, The unit cell structure of P2 is positioned perpendicular to the unit cell structure of O3, and Depending on the chemical composition ratio of the matrix structure of the layered transition metal oxides (LTMOs) under analysis, the unit cell structure is expanded, while some of the iron (Fe) ions within the lattice structure are replaced by manganese (Mn) ions and some of the sodium (Na) ions are removed, and A screening apparatus for dopants capable of suppressing the phase transition of layered transition metal oxides (LTMOs), characterized by being P2/O3-Na 0.85 Fe 0.5 Mn 0.5 O 2 stabilized through density functional theory (DFT) calculations.

Description

Dopant Screening Method of Layered Transition Metal Oxide with Multiple Phase and Apparatus Therewith for Suppressing Phase Transition of Layered Transition Metal Oxide with Multiple Phases The present invention relates to a method for selecting a dopant effective in suppressing the phase transition of a layered transition metal oxide (hereinafter referred to as 'LTMOs') having multiple phases, and to an apparatus used in such a method. [Assignment No.] 202417221040 [Project Title] Development of a Next-Generation Solid Electrolyte Material Screening Platform: Deep Learning Generative Models and Bayesian [Project Organizing Agency] National Research Foundation of Korea [Project Period] Mar. 1, 2024 – Feb. 28, 2025 Lithium-ion rechargeable batteries have been used as energy storage devices in various fields of electronic technology, and with the recent surge in demand for lithium-ion rechargeable batteries, sodium-ion rechargeable batteries are attracting attention as a replacement for lithium, an expensive metal. Since these sodium-ion rechargeable batteries have an insertion/extraction reaction mechanism similar to that of conventional lithium-ion rechargeable batteries, they are one of the representative next-generation materials with high potential for application in next-generation rechargeable batteries. Layered transition metal oxides, which are representative forms of cathode active materials, possess high energy density, specific capacity, and a simple structure. They also have excellent electrochemical performance and are easy to synthesize, making them suitable for mass production. They are classified into O3 and P2 types depending on the position of the sodium ion; among these, cathode active materials with a P2 crystal structure have the advantages of relatively high atmospheric and moisture stability and being less sensitive to synthesis conditions such as temperature and atmosphere. However, because sodium ions with large ionic radii change the lattice structure during insertion/extraction within the layered structure, the cathode active material continuously undergoes phase transitions. Consequently, the irreversible phases generated during this process lead to a problem where the cycle life and high-rate characteristics of sodium-ion secondary batteries are degraded (Korean Patent Publication No. 2024-0065529, published May 14, 2024). As such, sodium ion-based layered transition metal oxides (LTMOs) are receiving significant attention as excellent candidates for cathode materials due to their various advantages. Among these, single-phase LTMOs of the P2 and O3 types, which have been extensively studied, suffer from phase transition problems during the battery charging and discharging process, in which the existing phase changes to a different phase. Typically, single-phase P2 type LTMOs undergo a phase transition to the O2 type, while single-phase O3 type LTMOs change to the P3 type. Due to these phase transitions, structural instability of the cathode material and uneven diffusion of sodium ions may occur, and battery performance may deteriorate due to irreversible structural distortion and large volume changes. Compared to single-phase LTMOs, it is known that P2/O3 type LTMOs with multiple phases possess the advantages of both different single-phase structures and suppress phase transitions, so various experimental analyses of P2/O3 type multiphase LTMOs are being performed. However, LTMOs with multiple phases can still experience phase transition issues, and research on LTMOs with multiple phases is also lacking. This is because, unlike single-phase LTMOs, for which atomic arrangement information is well known, structural information for multiphase LTMOs has been provided only in a very limited manner. To fully solve the phase transition problem of P2/O3 type LTMOs with multiple phases, one could consider a method of evaluating them after doping with various elements in actual experiments, but it is difficult to rapidly investigate a large number of doping structures due to the lack of relevant structural information and difficulties in the synthesis process. Figure 1 is a schematic diagram of the crystal structure of a stacked transition metal oxide used in an embodiment of the present invention. Figure 2 schematically illustrates the steps of the process of selecting a dopant of a stacked transition metal oxide according to the present invention. Figure 3(a) is a schematic diagram of P2/O3 phase LTMOs, and 3(b) is a schematic diagram of the phase transition process due to the slip phenomenon of the transition metal layer. Figure 4 shows the results of calculating the energy difference before and after the phase transition of the P2 phase (a) and O3 phase (b) for each dopant. Figure 5 shows the results of calculating the average Na ion layer thickness (a) and the change in thickness of the P2 Na layer (b) before and after the phase transition. Figure 6 shows the results of calculating th