Cathode active material for lithium secondary battery, preparation method thereof, cathode including cathode active material, and lithium secondary battery including cathode

Patent metadata

Field	Value
Publication number	US-2021126256-A1
Application number	US-202017081125-A
Country	US
Kind code	A1
Filing date	Oct 27, 2020
Priority date	Oct 29, 2019
Publication date	Apr 29, 2021
Grant date	—

Abstract

This application relates to a cathode active material for a lithium secondary battery, a method of preparing the cathode active material, a cathode employing the cathode active material, and a lithium secondary battery employing the cathode. The cathode active material may include a secondary particle in which primary particles are aggregated and a first coating layer disposed on the plurality of primary particles to have a thickness of about 2.5 nm or less and including a NiO-like crystalline phase belonging to a Fm3-m space group. The cathode active material may prevent surface deterioration through a washing process using a weakly acidic or neutral organic buffer, thereby improving the initial efficiency characteristic and life characteristics of the lithium secondary battery while maintaining the initial capacity of the lithium secondary battery.

First claim

What is claimed is:

1 . A cathode active material for a lithium secondary battery, the cathode active material comprising:
a secondary particle comprising a plurality of primary particles; and a first coating layer disposed on the primary particles to have a thickness of about 2.5 nm or less, the first coating layer comprising a NiO-like crystalline phase belonging to a Fm3-m space group.

2 . The cathode active material of claim 1 , wherein the primary particles comprise a nickel-based lithium transition metal oxide in which a content of nickel in a transition metal is about 70 mol % or more.

3 . The cathode active material of claim 1 , wherein the primary particles comprise a lithium transition metal oxide represented by Formula 1 below:
Li a Ni b M1 c M2 d O 2   [Formula 1]
wherein, M1 is at least one element selected from Co, Mn, and Al, M2 is at least one element selected from B, Mg, Ti, Ca, Na, K, Sr, Cr, V, Fe, Cu, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, Ba, and rare-earth elements, and 0.9≤a≤1.1, 0.7≤b<1.0, 0<c≤0.3, 0≤d≤0.1, and 0.95≤b+c+d≤1.05 are satisfied.

4 . The cathode active material of claim 1 , wherein the primary particles comprise a lithium transition metal oxide represented by Formula 2 below:
Li a Ni b Co c′ M1 c″ M2 d′ O 2   [Formula 2]
wherein, M1′ is at least one element selected from Mn and Al, M2 is at least one element selected from B, Mg, Ti, Ca, Na, K, Sr, Cr, V, Fe, Cu, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, Ba, and rare-earth elements, and 0.9≤a≤1.1, 0.7≤b<1.0, 0<c′≤0.3, 0<c″≤0.3, 0<c′+c″≤0.3, 0≤d′≤0.1, and b+c′+c″+d′=1 are satisfied.

5 . The cathode active material of claim 2 , wherein the nickel-based lithium transition metal oxide comprises a layered crystalline phase belonging to a R-3m space group.

6 . The cathode active material of claim 1 , wherein:
the primary particles have an average particle diameter of about 50 nm to about 2 μm, and wherein the secondary particle, comprising the primary particles, has an average particle diameter of about 1 μm to 50 μm.

7 . The cathode active material of claim 1 , wherein the secondary particle further comprises a second coating layer on a portion of a surface of the secondary particle, the second coating layer containing a metal compound of cobalt (Co) and at least one selected from Group 2 elements, Group 12 elements, and Group 13 elements.

8 . The cathode active material of claim 7 , wherein the metal compound comprises a metal alloy, a metal oxide, a metal sulfide, a metal chloride, a metal nitride, a metal fluoride, a metal phosphide, a metal alkoxide, or a combination thereof.

9 . The cathode active material of claim 7 , wherein the content of the metal oxide is about 0 parts by weight to about 5 parts by weight based on 100 parts by weight of the lithium metal oxide included in the second particle.

10 . The cathode active material of claim 7 , wherein the second coating layer is uniformly formed on the surface of the secondary particle to have a thickness of about 1 μm or less.

11 . A cathode comprising the cathode active material of claim 1 .

12 . A lithium secondary battery comprising the cathode of claim 11 .

13 . A method of preparing the cathode active material of claim 1 , the method comprising:
primarily heat-treating a mixture comprising a transition metal precursor and a lithium source; washing the primarily heat-treated mixture using a solvent comprising a weakly acidic or neutral organic buffer to obtain a washed mixture; and secondarily heat-treating the washed mixture.

14 . The method of claim 13 , wherein the organic buffer comprises an amphiphilic organic compound having a sulfone group.

15 . The method of claim 14 , wherein the amphiphilic organic compound having a sulfone group comprises at least one selected from the group consisting of MOPS (3-(N-morpholino)propanesulfonic acid), MES (2-(N-morpholino)ethanesulfonic acid), HEPES (2-[4-(2-hydroxyethyl)piperazin-1-yl] ethanesulphonic acid), PIPES (1,4-piperazindieethanesulfonic acid), TES (N-tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid), ACES (2-(carbamoylmethylamino)ethanesulfonic acid), BES (N,N-bis(2-hydroxyl-2-amino)ethanesulfonic acid), and CHES ((cyclohexylamino)ethanesulfonic acid).

16 . The method of claim 13 , wherein the organic buffer is comprised in the solvent in a concentration of about 0.001 M to about 2 M.

17 . The method of claim 13 , wherein the organic buffer is added to the solvent one or more times during the washing.

18 . The method of claim 13 , wherein, in the washing of the resulting product, a coating material for surface-coating the cathode active material is further introduced into the solvent.

19 . The method of claim 13 , wherein the mixture is prepared by a dry mixing method.

20 . The method of claim 13 , wherein at least one of the primary heat treatment and the secondary heat treatment is performed at about 600° C. to about 1000° C. under an air or oxygen atmosphere.

Assignees

• Samsung Sdi Co Ltd

Inventors

• Shin Dongwook
• Park Jinhwan

Classifications

• C01G53/42

  containing alkali metals, e.g. LiNiO2 · CPC title

• H01M10/052

  Li-accumulators · CPC title

• H01M4/366 Primary

  as layered products · CPC title

• H01M4/525 Primary

  of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy · CPC title

• H01M4/0471

  involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis · CPC title