KR-102962560-B1 - MANUFACTURING METHOD OF HIGH PERFORMANCE LITHIUM IRON PHOSPHATE CATHODE MATERIALS THROUGH MICRO-CRYSTALLIZATION METHOD

Abstract

The present invention relates to a method for manufacturing a lithium iron phosphate cathode active material, and more specifically, comprises: a first step of manufacturing iron phosphate hydrate ( FePO₄ · xH₂O ) using a precipitation method; a second step of manufacturing iron phosphate dihydrate ( FePO₄ · 2H₂O ) from the iron phosphate hydrate ( FePO₄ ·xH₂O) through a microcrystallization process; a third step of manufacturing an iron phosphate ( FePO₄ ) precursor by heat-treating the iron phosphate dihydrate ( FePO₄ · 2H₂O ) powder; and a fourth step of manufacturing a lithium iron phosphate precursor powder for heat treatment by mixing lithium carbonate and dextrose with the iron phosphate ( FePO₄ ) precursor powder and milling it using a planetary ball mill. The present invention provides a method for manufacturing a lithium iron phosphate cathode active material, characterized by including a fifth step of manufacturing a lithium iron phosphate ( LiFePO₄ ) cathode active material by performing a first heat treatment and a second heat treatment on the above-mentioned lithium iron phosphate precursor powder for heat treatment.

Inventors

• 유현덕
• 권우정
• 홍정기
• 모한티 상그람 케샤리
• 정태호

Assignees

• 부산대학교 산학협력단

Dates

Publication Date

20260507

Application Date

20240223

Claims (7)

1. The method comprises: a first step of preparing iron phosphate hydrate ( FePO₄ · xH₂O ) using a precipitation method; a second step of preparing iron phosphate dihydrate ( FePO₄ · 2H₂O ) from the iron phosphate hydrate ( FePO₄ · xH₂O ) through a microcrystallization process; a third step of preparing an iron phosphate ( FePO₄ ) precursor by heat-treating the iron phosphate dihydrate ( FePO₄ · 2H₂O ); a fourth step of preparing a lithium iron phosphate precursor powder for heat treatment by milling lithium carbonate and dextrose onto the iron phosphate ( FePO₄ ) precursor using a planetary ball mill; and a fifth step of preparing a lithium iron phosphate ( LiFePO₄ ) cathode active material by performing a first heat treatment followed by a second heat treatment on the lithium iron phosphate precursor powder for heat treatment. The first step above involves preparing iron phosphate hydrate ( FePO₄ · xH₂O ) by stirring ferrous sulfate heptahydrate (FeSO₄· 7H₂O ), phosphoric acid ( H₃PO₄ ), an oxidizing agent, and a complexing agent; the second step above involves preparing iron phosphate dihydrate ( FePO₄ · 2H₂O ) by microcrystallizing the iron phosphate hydrate ( FePO₄ · xH₂O ) under conditions where pH , temperature, and the concentration of phosphoric acid are controlled. A method for manufacturing a lithium iron phosphate cathode active material, characterized by maintaining the pH at 3 to 5 and the temperature at 50 to 70°C and stirring in the first step, and adding 1 to 3 moles of phosphoric acid per 1 mole of iron phosphate hydrate ( FePO₄ · xH₂O ) and maintaining the pH at 1 to 3 and the temperature at 80 to 100°C while stirring in the second step.
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4. In Article 1, A method for manufacturing a lithium iron phosphate cathode active material, characterized in that the heat treatment conditions of the third step above involve heat treatment at 400 to 600℃ for 1 to 10 hours.
5. In Article 1, The above fourth step is characterized by mixing the lithium carbonate at a molar ratio of 1.0 to 1.05 moles per 1 mole of the iron phosphate ( FePO₄ ) precursor, and mixing the dextrose at a ratio of 10 to 20 parts by weight per 100 parts by weight of the iron phosphate ( FePO₄ ) precursor mixture mixed with lithium carbonate.
6. In Article 1, The above fourth step is characterized by milling at a speed of 100 to 500 rpm for 1 to 10 hours, a method for manufacturing a lithium iron phosphate cathode active material.
7. In Article 1, A method for manufacturing a lithium iron phosphate cathode active material, characterized in that the first heat treatment condition of the above 5th step is heat treatment at 300 to 400℃ for 3 to 7 hours, and the second heat treatment condition is heat treatment at 600 to 700℃ for 10 to 20 hours.

Description

Manufacturing Method of High Performance Lithium Iron Phosphate Cathode Materials Through Micro-Crystallization Method The present invention relates to a method for manufacturing a lithium iron phosphate cathode active material, and more specifically, to a method for manufacturing a lithium iron phosphate cathode active material that improves electrochemical performance by reducing the size of the generated primary particles and optimizing the microcrystalline structure. Lithium iron phosphate ( LiFePO₄ ) is a cathode active material for lithium-ion batteries that possesses high structural and thermal stability and excellent lifespan characteristics based on strong PO bonding. However, it has limitations in electrochemical properties due to low electrical and ionic conductivity. Therefore, attempts are being made to improve electrical conductivity through carbon coating, transition metal doping, or by reducing particle size during the formation process. These attempts have been carried out through hydrothermal synthesis methods, but they have disadvantages that make industrial application difficult due to process complexity, reduced energy density, and limitations in synthesis scale. Consequently, the need for a new synthesis method is emerging. Conventional inventions synthesized lithium iron phosphate using a hydrothermal synthesis method requiring high-pressure conditions, which made it difficult to scale up; however, a new precipitation method has been proposed that enables scale-up and allows for large-scale synthesis. Nevertheless, research on improving the quality of the iron phosphate precursor produced using this precipitation method is still lacking. This invention improves the quality of a precursor by adding a microcrystallization process during the synthesis of iron phosphate, a precursor of lithium iron phosphate, via a precipitation method capable of mass synthesis. In particular, to enhance applicability in actual industrial settings, this invention was completed using a crystallization method that utilizes temperature and pH without the use of additional raw materials. FIG. 1 is a schematic diagram showing a method for manufacturing a lithium iron phosphate ( LiFePO4 ) active material according to an embodiment of the present invention. FIG. 2 is a scanning electron microscope image of (A) amorphous iron phosphate hydrate prepared according to Comparative Example 1 of the present invention, (B) iron phosphate dihydrate on meta-Strengite I prepared according to Example 2, (C) iron phosphate dihydrate on meta-Strengite II prepared according to Example 3, and (D) iron phosphate dihydrate on Strengite prepared according to Example 1. Figure 3 shows the results of iron phosphate particle size analysis prepared according to Examples 1 and 3 of the present invention. Figure 4 is the X-ray diffraction pattern of FePO4 prepared according to Examples 1, 2, 3 and Comparative Example 1 of the present invention. Figure 5 shows the rate capability and lifespan characteristics of a battery manufactured with an active material prepared according to Examples 1, 2, and 3 and Comparative Example 1 of the present invention. The terms used in this invention have been selected based on currently widely used general terms, taking into account their functions within the invention; however, these terms may vary depending on the intent of those skilled in the art, case law, the emergence of new technologies, etc. Additionally, in specific cases, terms have been arbitrarily selected by the applicant, and in such cases, their meanings will be described in detail in the relevant description of the invention. Therefore, the terms used in this invention should be defined not merely by their names, but based on their meanings and the overall content of the invention. Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application. When a part of a specification is described as “comprising” a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. Embodiments of the present invention are described below with reference to the attached drawings so that those skilled in the art can easily implement them. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. The present invention will be described in detail below. To achieve the above-mentioned objective, a method for synthesizing a lithium iron phosphate cathode active material according to a