Lithium secondary battery

Patent metadata

Field	Value
Publication number	US-2017170474-A1
Application number	US-201615371936-A
Country	US
Kind code	A1
Filing date	Dec 7, 2016
Priority date	Dec 9, 2015
Publication date	Jun 15, 2017
Grant date	—

Abstract

Provided is a lithium secondary battery including a cathode containing a cathode active material in which a central part has a different concentration from a surface part, and a conductive material having a specific composition ratio, and specifically, a lithium secondary battery including a cathode containing a cathode active material in which a central part of one or more kinds of metals configuring the cathode active material has a different concentration from a surface part thereof, and two or more kinds of conductive materials mixed at a specific ratio, thereby having excellent stability and high low-temperature characteristic and high output characteristic as compared to a conventional lithium secondary battery.

First claim

What is claimed is:

1 . A lithium secondary battery comprising:
a cathode, an anode, an electrolyte, and a separator, wherein the cathode includes a cathode active material in which a transition metal concentration of a central part is different from that of a surface part, and a conductive material in which a carbon large surface area structure and a carbon small surface area structure are mixed at a weight ratio of 10:90 to 70:30.

2 . The lithium secondary battery of claim 1 , wherein the cathode active material includes the central part and the surface part in the order from an inside to an outside, the central part being represented by Chemical Formula 1 below, and the surface part being represented by Chemical Formula 2 below:
LiM1 X1 M2 Y1 M3 Z1 O w   [Chemical Formula 1]
LiM1 X2 M2 Y2 M3 Z2 O w   [Chemical Formula 2]
In Chemical Formulas 1 and 2, M1, M2, and M3 are selected from the group consisting of Ni, Co, Mn, Fe, Na, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga, B, and a combination thereof, 0.75≦X1≦0.9, 0.75≦X2≦0.9, 0≦Y1≦0.2, 0≦Y2≦0.2, 0.01≦Z1≦0.2, 0.01≦Z2≦0.2, 0≦W≦3, 0<X1+Y1+Z1≦1, 0<X2+Y2+Z2≦1, X2≦X1, Y1≦Y2, and Z1≦Z2, except that the Chemical Formula 1 and the Chemical Formula 2 are the same.

3 . The lithium secondary battery of claim 1 , wherein the cathode active material includes a first central part represented by Chemical Formula 3 below, a second central part represented by Chemical Formula 4 below, and the surface part represented by Chemical Formula 5 below in the order from an inside to an outside:
LiM1 X3 M2 Y3 M3 Z3 O W   [Chemical Formula 3]
LiM1 X4 M2 Y4 M3 Z4 O W   [Chemical Formula 4]
LiM1 X5 M2 Y5 M3 Z5 O W   [Chemical Formula 5]
in Chemical Formulas 3 to 5, M1, M2, and M3 are selected from the group consisting of Ni, Co, Mn, Fe, Na, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga, B, and a combination thereof, 0.75≦X3≦0.9, 0.75≦X4≦0.9, 0.75≦X5≦0.9, 0≦Y3≦0.2, 0≦Y4≦0.2, 0≦Y5≦0.2, 0.01≦Z3≦0.2, 0.01≦Z4≦0.2, 0.01≦Z5≦0.2, 0≦W≦3, 0<X3+Y3+Z3≦1, 0<X4+Y4+Z4≦1, 0<X5+Y5+Z5≦1, X5≦X4≦X3, Y3≦Y4≦Y5, Z3≦Z4≦Z5, except that the Chemical Formulas 3 to 5 are the same, respectively, or all of the Chemical Formulas 3 to 5 are the same.

4 . The lithium secondary battery of claim 1 , wherein the carbon large surface area structure and the carbon small surface area structure of the conductive material are mixed at the weight ratio of 20:80 to 40:60.

5 . The lithium secondary battery of claim 1 , wherein the carbon large surface area structure includes any one or two or more selected from graphene, single-walled carbon nanotube, and multi-walled carbon nanotube, and the carbon small surface area structure includes any one or two or more selected from fullerene, graphite, black lead, carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black, lamp black, thermal black, and Super-P.

6 . The lithium secondary battery of claim 2 , wherein in the Chemical Formulas 1 to 5, M1 is Ni, M2 is Co, and M3 is Mn.

7 . The lithium secondary battery of claim 3 , wherein in the Chemical Formulas 1 to 5, M1 is Ni, M2 is Co, and M3 is Mn.

8 . The lithium secondary battery of claim 2 , wherein the cathode active material satisfies Equations 1 and 2 below:
0.01≦|X1−X2|≦0.05   [Equation 1]
0.01≦|Z1−Z2|≦0.05   [Equation 2]

9 . The lithium secondary battery of claim 3 , wherein the cathode active material satisfies Equations 3 to 8 below:
0.01≦|X3−X4|≦0.05   [Equation 3]
0.01≦|X4−X5|≦0.05   [Equation 4]
0.01≦|X3−X5|≦0.01   [Equation 5]
0.01≦|Z3−Z4|≦0.05   [Equation 6]
0.01≦|Z4−Z5|≦0.04   [Equation 7]
0.01≦|Z3−Z5|≦0.01.   [Equation 8]

10 . The lithium secondary battery of claim 2 , wherein the cathode active material satisfies Equation 9 below:
0.5≦L 1 /L≦0.99   [Equation 9]
in Equation 9, L 1 is a distance from the center of the cathode active material to a boundary between the surface part and the central part, and L is a radius of an entire cathode active material.

11 . The lithium secondary battery of claim 3 , wherein the cathode active material satisfies Equations 10 and 11 below:
0.05≦L 2 /L≦0.5   [Equation 10]
0.01≦L 3 /L≦0.02   [Equation 11]
in Equation 10, L 2 is a distance from the center of the cathode active material to a boundary between the first central part and the second central part, L 3 is a distance from the boundary between the first central part and the second central part to a boundary between the second central part and the surface part, and L is a radius of an entire cathode active material.

Assignees

• Sk Innovation Co Ltd

Inventors

• Han Kook Hyun
• Yoo Kyung Bin
• Hwang Duck Chul

Classifications

• H01M4/505 Primary

  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

• H01M4/131

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

• H01M4/625

  Carbon or graphite · CPC title

• H01M10/0525 Primary

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