Cathode with Improved Structural Stability for Lithium Secondary Battery, Method for Manufacturing Same, and Lithium Secondary Battery Comprising Same

Patent metadata

Field	Value
Publication number	US-2024014379-A1
Application number	US-202218025580-A
Country	US
Kind code	A1
Filing date	May 6, 2022
Priority date	Jun 2, 2021
Publication date	Jan 11, 2024
Grant date	—

Abstract

Provided is a positive electrode for a lithium secondary battery with improved structural stability, a manufacturing method thereof, and a lithium secondary battery including the same. When the positive electrode containing a positive electrode additive is manufactured, the conditions of first and second rolling operations are controlled so that there is an advantage in that structures and electrical properties of a first mixture layer and a second mixture layer can be improved.

First claim

1 . A positive electrode for a lithium secondary battery, comprising:
a current collector; and a mixture layer formed on one surface or both surfaces of the current collector, wherein the mixture layer is a double-layer structure in which a first mixture layer and a second mixture layer are stacked, wherein the first mixture layer includes a positive electrode active material, a positive electrode additive represented by Chemical Formula 1 below, a conductive material, and a binder, and wherein a porosity of the first mixture layer ranges from 15% to 40%, and a porosity of the second mixture layer ranges from 40% to 70%:
Li p Co (1-q) M 1 q O 4 ,  [Chemical Formula 1]

in Chemical Formula 1, M 1 denotes one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and p and q are 5≤p≤7 and 0≤q≤0.5, respectively.

2 . The positive electrode of claim 1 , wherein:
an average thickness of the first mixture layer ranges from 0.1 μm to 20 μm; and an average thickness of the second mixture layer ranges from 50 μm to 300 μm.

3 . The positive electrode of claim 1 , wherein a ratio (D1:D2) of an average thickness (D1) of the first mixture layer to an average thickness (D2) of the second mixture layer ranges from 4:6 to 1:10.

4 . The positive electrode of claim 1 , wherein a content of the positive electrode additive ranges from 0.1 to 5 wt % based on a total weight of the first mixture layer.

5 . The positive electrode of claim 1 , wherein the positive electrode active material is a lithium metal composite oxide represented by Chemical Formula 2 below:
Li x [Ni y Co z Mn w M 2 v ]O u ,  [Chemical Formula 2]
in Chemical Formula 2, M 2 denotes one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and x, y, z, w, v, and u are 1.0≤x≤1.30, 0.1≤y<0.95, 0.01<z≤0.5, 0.01<w≤0.5, 0≤v≤0.2, and 1.5≤u≤4.5, respectively.

6 . A method of manufacturing a positive electrode for a lithium secondary battery, the method comprising:
forming a first mixture layer in a first mixture layer forming operation by applying a first slurry including a positive electrode active material and a positive electrode additive represented by Chemical Formula 1 below on one side or both sides of a current collector; rolling the formed first mixture layer in a first rolling operation; forming a second mixture layer in a second mixture layer forming operation by applying a second slurry including a positive electrode active material on the rolled first mixture layer; and rolling the formed second mixture layer in a second rolling operation, wherein a porosity of the first mixture layer ranges from 15 to 40%, and a porosity of the second mixture layer ranges from 40 to 70%: [Chemical Formula 1]
Li p Co (1-q) M 1 q O 4 ,
in Chemical Formula 1, M 1 denotes one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and p and q are 5≤p≤7 and 0≤q≤0.5, respectively.

7 . The method of claim 6 , wherein:
the first rolling operation is performed at a speed ranging from 0.5 m/s to 6 m/s; the second rolling operation is performed at a speed ranging from 2 m/s to 7 m/s; and the second rolling operation is performed at a faster speed than the first rolling operation.

8 . The method of claim 6 , wherein:
the first rolling operation is performed at a temperature ranging from 10° C. to 40° C.; and the second rolling operation is performed at a temperature ranging from 40° C. to 100° C.

9 . The method of claim 6 , wherein the first mixture layer satisfies a thickness change rate condition of Equation 1 below:
D 2 min /D 1 max ×100≥70%,  [Equation 1]
in Equation 1, D 1 max denotes a maximum thickness of the first mixture layer after the first rolling operation, and D 2 min denotes a minimum thickness of the first mixture layer after the second rolling operation.

10 . A lithium secondary battery comprising:
the positive electrode according to claim 1 ; a negative electrode; and a separator interposed between the positive electrode and the negative electrode.

11 . The lithium secondary battery of claim 10 , wherein:
the negative electrode includes a negative electrode current collector and a negative electrode mixture layer which is located on the negative electrode current collector and contains a negative electrode active material; and the negative electrode active material includes a carbon material and a silicon material.

Assignees

• Lg Energy Solution Ltd

Inventors

• Kim Gwang Yeon
• Oh Sang Seung
• Kim Hye Hyeon
• Jo Chi Ho

Classifications

• H01M4/1391 Primary

  of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx · CPC title

• H01M4/505

  of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy · CPC title

• H01M4/525

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

• H01M4/0435

  Rolling or calendering · CPC title

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title