KR-20260063154-A - Cathode Active Material and Secondary Battery Including the Same

Abstract

The present invention provides a positive electrode active material characterized by having at least two peaks in a particle size distribution (PSD) graph, and a ratio (A/B) of the area of the region of 0.1 to 1 μm (A) and the area of the region exceeding 1 μm (B) based on the horizontal axis point of 1 μm being 0.7 to 1.6.

Inventors

• 박다정
• 이준성
• 박상희
• 권태현
• 김현정
• 김진현
• 권혁원
• 공기영

Assignees

• 주식회사 엘 앤 에프

Dates

Publication Date

20260507

Application Date

20241030

Claims (14)

1. At least two peaks exist in the particle size distribution (PSD) graph, and A positive electrode active material characterized by a ratio (A/B) of the area (A) of the 0.1 to 1 µm region and the area (B) of the region exceeding 1 µm being 0.7 to 1.6 based on a point of 1 µm on the horizontal axis.
2. A positive active material according to claim 1, characterized in that the positive active material has a composition represented by the following chemical formula 1: Li x MP a O b (1) In the above formula, 0<x≤2, 0≤a≤2, 0<b≤4; M includes Fe and optionally may further include one or more of the following: transition metals of groups 3 to 12 excluding Fe, post-transition metals and metalloids of groups 13 to 15, alkaline earth metals, nonmetals of groups 14 to 16, lanthanides, and actinides.
3. A positive electrode active material according to claim 2, comprising Fe₂P and Li₃PO₄ , wherein the content of Fe₂P is greater than that of Li₃PO₄ on a weight basis.
4. A positive electrode active material according to claim 3, characterized in that the calcination process for manufacturing the LFP positive electrode active material is set to be carried out in a reducing atmosphere.
5. A positive electrode active material according to claim 4, characterized in that the reducing atmosphere is achieved by adding hydrogen gas to an inert gas.
6. A positive electrode active material according to claim 3, characterized in that the weight ratio of Fe₂P content to Li₃PO₄ content is 1.5 or higher.
7. A positive electrode active material according to claim 3, characterized in that the content of Fe 2 P is 1.3 to 2.9 wt%.
8. A positive electrode active material according to claim 3, characterized in that the content of Li₃PO₄ is 0.6 to 1.2 wt%.
9. A positive electrode active material according to claim 1, characterized in that the pellet density (PD) is 2.45 g/cc or higher.
10. A positive electrode active material according to claim 9, characterized in that the pellet density is achieved by including polyethylene glycol (PEG) as a carbon source for carbon coating on the particle surface of the positive electrode active material.
11. A positive electrode active material according to claim 9, characterized in that the pellet density is achieved by calcination in a reducing atmosphere.
12. A positive electrode active material according to claim 1, characterized in that the highest points of the two peaks are located in the 0.1 to 1 μm region and the greater than 1 μm region, respectively.
13. A positive active material according to claim 12, characterized in that the highest point of the second peak located on area (B) has a height equal to or greater than the highest point of the first peak located on area (A).
14. A secondary battery characterized by including a positive electrode active material according to claim 1.

Description

Cathode Active Material and Secondary Battery Including the Same The present invention relates to a positive electrode active material and a secondary battery comprising the same, and more specifically, to a positive electrode active material in which the area ratio of small particles to large particles based on an arbitrary particle size in a particle size distribution graph is within a specific range, and a secondary battery comprising the same. Lithium iron phosphate (LFP), whose usage has been increasing recently, offers many advantages in terms of thermal stability, electrochemical stability, eco-friendliness, and cost. On the other hand, it has the disadvantages of low energy density and low electron conductivity. Therefore, although improvements such as carbon coating on particle surfaces and particle micronization have been proposed to enhance electronic conductivity, these measures do not solve the problem of low energy density. Furthermore, due to the low pellet density (PD) of LFP, the amount of active material that can be packed within the same volume under the same conditions is reduced, which leads to lower energy density. In this regard, incorporating large particles or aggregates into the cathode active material increases pellet density through their relationship with small particles, but tends to degrade electrochemical properties. Specifically, while energy density improves with higher pellet density, the aggregation of nano-sized particles as pellet density increases reduces the specific surface area; consequently, this highlights the issue of reduced conductivity and leads to a decrease in overall capacity. Therefore, there is a high need in the industry for new technologies that can simultaneously improve energy density and conductivity in LFP cathode active materials. FIG. 1a is an FE-SEM image of the positive electrode active material of Example 2 in Experimental Example 1; FIG. 1b is EDS data for the positive electrode active material of Example 2 in Experimental Example 1; FIG. 2a is an FE-SEM image of the positive electrode active material from Experimental Example 1 to Comparative Example 3; FIG. 2b is EDS data for the positive electrode active materials of Experimental Example 1 to Comparative Example 3; Figure 3 is a graph showing the rate characteristic retention of Example 2 and Comparative Example 3 in Experimental Example 2. The present invention will be described further below with reference to embodiments thereof, but the scope of the invention is not limited by them. [Comparative Example 1] A mixture of Li₂CO₃ as a lithium raw material and FePO₄ as a precursor (Li/Me molar ratio = 1.040) was mixed with a mixture of glucose and PEG as a carbon source (glucose:PEG weight ratio = 2:8) at approximately 10 wt% relative to the combined weight of the lithium raw material and the precursor, added to distilled water as a solvent so that the solid content was approximately 40%, and stirred for 1 hour to prepare a wet raw material. For the wet raw material prepared above, wet coarse grinding was performed using an Attrition mill (Nanointec Co.) equipped with Beads size Φ2.0mm as a coarse grinding device, with the pump pressure set to 300 rpm and the grinding speed to 1000 rpm, thereby adjusting the wet solution particle size D50 to 1.0 ~ 2.0 μm. Then, using a fine mill (Daehwa Tech Co.) as the fine grinding equipment, wet fine grinding was performed with the pump pressure set to 300 rpm and the grinding pressure set to 2200 ppm, and the wet solution D50 was adjusted to 0.3 ~ 0.5 μm. A wet fine grinding solution prepared in this way was used with a Spray dry Atomizer type TS-Minor, M02/4 (Ain System Co., Ltd.), with the spray pressure set to approximately 1.5 to 2.0 bar, the Atomizer spray rotation set to 17,000 to 36,000 rpm, the Atomizer spray inlet temperature set to approximately 300℃, and the outlet temperature set to approximately 100℃, and then spray drying was performed to produce a dried product. Then, 35 g of the dried product was placed into a small graphite sagger and introduced into a tuber furnace made of quartz, SH-FU-100LTG-3 (Samheung Energy Co.). At this time, the firing temperature was set to a range of 750 to 800°C, the heating rate was set to 2 to 5°C/min, and the firing time was set to 10 hours or less, and N₂ gas (99.999% purity) was injected at a rate of 5 L/min or more as a gas to maintain an inert atmosphere. The calcined product manufactured in this way was ground using an air jet mill, JM-LB (KM Tech Co., Ltd.), while maintaining a grinding pressure of 0.05 to 0.3 MPa and a feed pressure of 0.3 to 0.5 MPa to produce a LiFePO4 cathode active material. [Comparative Example 2] A LiFePO4 cathode active material was prepared in the same manner as Comparative Example 1, except that a mixture of glucose and PEG (glucose:PEG weight ratio = 4:6) was used as the carbon source. [Comparative Example 3] A LiFePO4 cathode active material was prepared in the same manner