US-12626918-B2 - Positive electrode active material for lithium secondary battery, method for preparing the same and lithium secondary battery comprising the same

US12626918B2US 12626918 B2US12626918 B2US 12626918B2US-12626918-B2

Abstract

A positive electrode active material includes at least one secondary particle including an agglomerate of primary macro particles. The average particle size of the primary macro particle is 2 μm or more. A ratio of the average particle size of the primary macro particle to an average crystal size of the primary macro particle is 8 or more. An average particle size of the secondary particle is 3 to 10 μm. The secondary particle includes a nickel-based lithium transition metal oxide. The primary macro particle does not crack in a rolling process under 9 tons. A method for preparing the positive electrode active material includes mixing a nickel-based transition metal oxide precursor having a tap density of 2.0 g/cc or less and a lithium precursor and performing primary sintering to form a primary sintered product and performing secondary sintering on the primary sintered product.

Inventors

Ji-Hye Kim
Byung-Chun Park
Jung-Min Han
Jong-Wook Heo
Wang-Mo Jung

Assignees

LG ENERGY SOLUTION, LTD.

Dates

Publication Date: 20260512
Application Date: 20211029
Priority Date: 20201029

Claims (13)

1 . A positive electrode active material for a lithium secondary battery, comprising: a secondary particle comprising an agglomerate of a primary macro particle, wherein an average particle size (D50) of the primary macro particle is 2 μm or more, wherein a ratio of the average particle size (D50) of the primary macro particle to an average crystal size of the primary macro particle is 8 or more, wherein an average particle size (D50) of the secondary particle is 3 to 10 μm, wherein the secondary particle comprises a nickel-based lithium transition metal oxide, wherein the primary macro particle does not crack in a rolling process of the at least one secondary particle under 9 tons, and wherein the positive electrode active material further comprises fine particles of 1 μm or less in an amount less than 10% after the rolling process of the positive electrode active material under 9 tons.
2 . The positive electrode active material for a lithium secondary battery according to claim 1 , wherein the average crystal size of the primary macro particle is 200 nm or more.
3 . The positive electrode active material for a lithium secondary battery according to claim 1 , wherein a ratio of the average particle size (D50) of the secondary particle to the average particle size (D50) of the primary macro particle is 2 to 4 times.
4 . The positive electrode active material for a lithium secondary battery according to claim 1 , wherein the nickel-based lithium transition metal oxide comprises LiaNi 1-x-y Co x M1 y M2 w O 2 , and wherein 1.0≤a≤1.5, 0≤x≤0.2, 0≤y≤0.2, 0≤w≤0.1, 0≤x+y≤0.2, M1 includes at least one of Mn or Al, and M2 includes at least one of Ba, Ca, Zr, Ti, Mg, Ta, Nb or Mo.
5 . The positive electrode active material for a lithium secondary battery according to claim 1 , wherein the positive electrode active material further comprises a sintering additive, the sintering additive including at least one of zirconium, yttrium or strontium.
6 . The positive electrode active material for a lithium secondary battery according to claim 1 , wherein the positive electrode active material is further coated on a surface thereof with a boron containing material.
7 . The positive electrode active material for a lithium secondary battery according to claim 1 , wherein the positive electrode active material is further coated on a surface thereof with a cobalt containing material.
8 . A positive electrode for a lithium secondary battery comprising a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, the positive electrode active material layer comprising the positive electrode active material according to claim 1 .
9 . A lithium secondary battery comprising a positive electrode comprising the positive electrode active material according to claim 1 .
10 . A method for preparing a positive electrode active material for a lithium secondary battery, the method comprising: (S1) mixing a nickel-based transition metal oxide precursor having a tap density of 2.0 g/cc or less and a lithium precursor and performing primary sintering to form a primary sintered product; and (S2) performing secondary sintering on the primary sintered product, wherein the positive electrode active material for a lithium secondary battery is as defined in claim 1 .
11 . The method for preparing a positive electrode active material for a lithium secondary battery according to claim 10 , wherein a temperature of the primary sintering is 780 to 900° C.
12 . The method for preparing a positive electrode active material for a lithium secondary battery according to claim 10 , wherein a temperature of the secondary sintering is 650 to 800° C.
13 . The method for preparing a positive electrode active material for a lithium secondary battery according to claim 10 , wherein the method does not comprise washing between the primary sintering (S1) and the secondary sintering (S2).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a national phase entry under 35 U.S.C. § 371 of International Application No. PCT/KR2021/015485, filed on Oct. 29, 2021, which claims priority to Korean Patent Application No. 10-2020-0142376 filed on Oct. 29, 2020, in the Republic of Korea, the disclosures of which are incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to a positive electrode active material for a lithium secondary battery comprising primary macro particles and a method for preparing the same. BACKGROUND ART Recently, with the widespread use of electronic devices using batteries, for example, mobile phones, laptop computers and electric vehicles, there is a fast growing demand for secondary batteries with small size, light weight and relatively high capacity. In particular, lithium secondary batteries are gaining attention as a power source for driving mobile devices due to their light weight and high energy density advantages. Accordingly, there are many efforts to improve the performance of lithium secondary batteries. A lithium secondary battery includes an organic electrolyte solution or a polymer electrolyte solution filled between a positive electrode and a negative electrode made of an active material capable of intercalating and deintercalating lithium ions, and produces electrical energy by oxidation and reduction reactions during intercalation/deintercalation of lithium ions at the positive electrode and the negative electrode. The positive electrode active material of the lithium secondary battery includes lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMn2O4) and a lithium iron phosphate compound (LiFePO4). Among them, lithium cobalt oxide (LiCoO2) is widely used due to its high operating voltage and large capacity advantages, and is used as a positive electrode active material for high voltage. However, there is a limitation in the use of a large amount of cobalt (Co) as a power source in the field of electric vehicles due to its price rise and unstable supply, and thus there is a need for development of a positive electrode active material as an alternative. Accordingly, nickel cobalt manganese based lithium composite transition metal oxide (hereinafter simply referred to as ‘NCM based lithium composite transition metal oxide’) with partial substitution of nickel (Ni) and manganese (Mn) for cobalt (Co) has been developed. Meanwhile, as shown in FIG. 1, the conventional NCM based lithium composite transition metal oxide is in the form of a secondary particle formed by agglomeration of primary micro particles, and has a large specific surface area and low particle rigidity, and when an electrode is made of the positive electrode active material comprising secondary particles formed by agglomeration of primary micro particles and undergoes a rolling process as shown in FIG. 1, a large amount of gas is produced during cell operation due to severe particle cracking, resulting in low stability. In particular, high-Ni NCM based lithium composite transition metal oxide with high capacity has low structural and chemical stability and is more difficult to ensure thermal stability. DISCLOSURE Technical Problem The present disclosure is directed to providing a positive electrode active material in the form of a secondary particle having the average particle size D50 of the same or similar level to the conventional art, comprising primary macro particles as opposed to the conventional art, thereby minimizing particle cracking in a rolling process. Accordingly, the present disclosure is further directed to providing a nickel-based positive electrode active material with high press density, long life and good gas performance. Technical Solution An aspect of the present disclosure provides a positive electrode active material for a lithium secondary battery according to the following embodiment. A first embodiment relates to a positive electrode active material for a lithium secondary battery comprising a secondary particle comprising an agglomerate of a primary macro particle, wherein an average particle size D50 of the primary macro particle is 2 μm or more, a ratio of the average particle size D50 of the primary macro particle/an average crystal size of the primary macro particle is 8 or more, an average particle size (D50) of the secondary particle is 3 to 10 μm, the secondary particle comprises a nickel-based lithium transition metal oxide, and the primary macro particle does not crack in a rolling process of the at least one secondary particle under 9 tons. A second embodiment relates to the positive electrode active material for a lithium secondary battery according to the first embodiment, wherein the average crystal size of the primary macro particle is 200 nm or more. A third embodiment relates to the positive electrode active material for a lithium secondary battery according to the fi