KR-20260064787-A - POSITIVE ELECTRODE ACTIVE MATERIAL, POSITIVE ELECTRODE COMPRISING THE SAME, AND LITHIUM SECONDARY BATTERY

Abstract

The present invention relates to a positive electrode active material, a positive electrode containing the same, and a lithium secondary battery.

Inventors

• 신은정
• 이원균
• 권오민
• 김현우
• 홍유식
• 한원상

Assignees

• 주식회사 엘지화학

Dates

Publication Date

20260508

Application Date

20241029

Claims (10)

1. A bimodal type positive electrode active material comprising a first lithium iron phosphate-based compound as a subatomic particle and a second lithium iron phosphate-based compound as an allotrope, having an angle of internal friction (AIF) of 33 to 35 degrees, The molar ratio of the first lithium iron phosphate-based compound and the second lithium iron phosphate-based compound is 1:3.5 to 1:4.5, and When the PSD (Particle Size Distribution) graph is represented by Equation 1 below, the first lithium iron phosphate-based compound has μ = -2 and σ = 1.6, and the second lithium iron phosphate-based compound has μ = 1.65 and σ = 0.58, for the positive electrode active material: [Equation 1] In the above Equation 1, x is the particle size (㎛), and y is the volume percentage (%).
2. In claim 1, The above positive active material is a positive active material having a flow function greater than 4.
3. In claim 1, The above positive active material is a positive active material having a cohesion of 0.8 kPa to 0.9 kPa.
4. In claim 1, The above first lithium iron phosphate-based compound is a positive electrode active material having an average particle size (D 50 ) of 0.1 μm to 0.5 μm.
5. In claim 1, The above second lithium iron phosphate-based compound is a positive electrode active material having an average particle size (D 50 ) of 2㎛ to 4㎛.
6. In claim 1, The above positive active material has an average particle size (D 50 ) of 1 μm to 6 μm.
7. In claim 1, The above first lithium iron phosphate-based compound and second lithium iron phosphate-based compound are positive electrode active materials comprising a coating layer containing carbon (C).
8. In claim 1, A positive electrode active material wherein the first lithium iron phosphate-based compound and the second lithium iron phosphate-based compound each independently have a composition represented by the following chemical formula 1: [Chemical Formula 1] Li 1+x Fe 1-a M a PO 4 In the above chemical formula 1, M is one or more selected from Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, Na, Si, Ca, B, and Y, and -0.2≤x≤0.2, 0≤a≤0.9.
9. A positive electrode comprising a positive electrode active material according to any one of claims 1 to 8.
10. A lithium secondary battery comprising a positive electrode according to claim 9.

Description

Positive electric active material, positive electric component comprising the same, and lithium secondary battery The present invention relates to a positive electrode active material, a positive electrode containing the same, and a lithium secondary battery. With the increasing technological development and demand for mobile devices, the demand for rechargeable batteries as an energy source is rapidly rising. Among these rechargeable batteries, lithium-ion batteries, which possess high energy density and voltage, long cycle life, and low self-discharge rates, have been commercialized and are widely used. Lithium secondary batteries consist of four major components: a positive electrode, a negative electrode, a separator, and an electrolyte. Among these, the positive electrode active material, which is included in the positive electrode, plays a significant role in determining the battery's capacity, output, and lifespan. Currently used positive electrode active materials include NCM-based positive electrode active materials containing nickel, cobalt, manganese, and/or aluminum, and LFP (lithium iron phosphate)-based positive electrode active materials. Meanwhile, improving the performance of the positive electrode active material is essential for lithium secondary batteries to have high energy density, output, and lifespan; consequently, much research is currently being conducted to develop high-performance positive electrode active materials. LFP having an olivin structure is a promising active material that has excellent lifespan characteristics and superior advantages in all safety aspects, including overcharging and over-discharging, because it has the best structural stability. In particular, LFP has excellent high-temperature stability due to the strong bonding force of PO4, and because it contains iron, which is resource-abundant and inexpensive, it is cheaper than the aforementioned LiCoO2, LiNiO2, or LiMn2O4, and because it has low toxicity, it has less impact on the environment. However, since LFP has low electrical conductivity, there is a problem that the internal resistance of the battery increases when LFP is used as a positive electrode active material. As a result, the battery capacity decreases as the polarization potential increases when the battery circuit is closed. In addition, LFP has a limitation in that it cannot sufficiently increase the energy density of the battery because its density is lower than that of conventional positive electrode active materials, and there is a problem of low output characteristics because it typically takes the form of secondary particles assembled from primary particles, which results in high interfacial resistance between primary particles. To address this, a method has been proposed to increase output by reducing resistance through the manufacturing of LFP as nanoparticles and coating with highly conductive carbon. However, even if the LFP active material is coated with carbon, the initial 5 sec resistance is high, resulting in a significant initial voltage drop (IR drop) at low temperatures, which is insufficient for the output characteristics required for medium and large-sized devices. Figure 1 shows the PSD graph of the positive electrode active materials of Comparative Example 1 and Comparative Example 2. Figure 2 shows the PSD graphs of the positive electrode active materials of Comparative Example 1, Comparative Examples 3 to 5. Figure 3 shows the PSD graphs of the positive electrode active materials of Example 1, Comparative Example 3, Comparative Example 6, and Comparative Example 7. Figure 4 shows the PSD graph of the positive electrode active materials of Comparative Examples 8 to 11. Hereinafter, the present invention will be described in more detail to aid in understanding the invention. Terms and words used in the description and claims of the present invention shall not be interpreted as being limited to their ordinary or dictionary meanings, and shall be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention. In this specification, a single-particle cathode active material refers to a cathode active material composed of 10 or fewer primary particles, as opposed to a spherical secondary particle cathode active material formed by the aggregation of tens to hundreds of primary particles. Specifically, in this specification, the single-particle cathode active material may be a single particle composed of one primary particle, or it may be a secondary particle formed by the aggregation of several primary particles. In this case, 'primary particle' refers to the smallest unit of a particle recognized when observing the cathode active material through a scanning electron microscope, and 'secondary particle' refers to a secondary structure formed by the aggregation of multiple p