DE-102025146564-A1 - Cathode for a lithium secondary battery and lithium secondary battery containing this

DE102025146564A1DE 102025146564 A1DE102025146564 A1DE 102025146564A1DE-102025146564-A1

Abstract

A cathode for a lithium secondary battery comprises a cathode current collector and sequentially stacked first and second cathode active material layers on its surface. The first cathode active material layer includes a first conductive material and either a first cathode active material with a single-particle structure or a mixture of the first and a second cathode active material with a secondary particle structure. The second cathode active material layer includes a second conductive material and either the second cathode active material or a mixture of the first and second cathode active materials. The content of the first cathode active material in the first cathode active material layer is greater than the content of the second cathode active material, while the content of the second cathode active material in the second cathode active material layer is greater than or equal to that of the first.

Inventors

Seong Cho KWON
Hwan Ho Jang
Sang Won Park

Assignees

SK ON CO., LTD.

Dates

Publication Date: 20260513
Application Date: 20251111
Priority Date: 20241111

Claims (14)

Cathode for a lithium secondary battery, comprising: a cathode current collector; and a first cathode-active material layer and a second cathode-active material layer stacked successively on a surface of the cathode current collector, whereby the first cathode-active material layer comprises a first conductive material and either a first cathode-active material with a single-particle structure or a mixture of the first cathode-active material and a second cathode-active material with a secondary-particle structure, whereby the second cathode-active material layer comprises a second conductive material and either the second cathode-active material or a mixture of the first cathode-active material and the second cathode-active material, whereby in the first cathode-active material layer the content of the first cathode-active material is greater than the content of the second cathode-active material, based on the total weight of the first cathode-active material layer, whereby in the second cathode-active material layer the content of the second cathode-active material is greater than or equal to the content of the first cathode-active material, based on the total weight of the second Cathode active material layer, and where the content of the first conductive material in the first cathode active material layer, based on the total weight of the first cathode active material layer, is greater than the content of the second conductive material in the second cathode active material layer, based on the total weight of the second cathode active material layer.
Cathode for a lithium secondary battery according to Claim 1 , wherein the content of the first cathode active material in the first cathode active material layer, based on the total weight of the first cathode active material layer, is 50 wt.% to 99 wt.% and the content of the second cathode active material in the first cathode active material layer, based on the total weight of the first cathode active material layer, is less than 50 wt.%.
Cathode for a lithium secondary battery according to Claim 1 , wherein the content of the first cathode active material in the second cathode active material layer, based on the total weight of the second cathode active material layer, is less than 50 wt.% and the content of the second cathode active material in the second cathode active material layer, based on the total weight of the second cathode active material layer, is 50 wt.% to 99 wt.%.
Cathode for a lithium secondary battery according to Claim 1 , wherein the content of the first conductive material in the first cathode active material, based on the total weight of the first cathode active material layer, is 0.5 wt.% to 1.5 wt.%.
Cathode for a lithium secondary battery according to Claim 1 , wherein the content of the second conductive material in the second cathode active material layer, based on the total weight of the second cathode active material layer, is 0.1 wt.% to 0.8 wt.%.
Cathode for a lithium secondary battery according to Claim 1 , wherein the ratio of the content of the first conductive material in the first cathode active material layer, based on the total weight of the first cathode active material layer, to the content of the second conductive material in the second cathode active material layer, based on the total weight of the second cathode active material layer, is greater than 1 and less than or equal to 1.6.
Cathode for a lithium secondary battery according to Claim 1 , wherein the first conductive material and the second conductive material each independently comprise at least one selected from the group consisting of single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), carbon black, Denka carbon black and mixtures thereof.
Cathode for a lithium secondary battery according to Claim 1 , wherein the first cathode active material and the second cathode active material each independently consist of a lithium metal oxide with a nickel content of comprise 80 mol% to 99 mol%, based on the total molar amount of elements excluding lithium and oxygen.
Lithium secondary battery, comprising: the cathode for a lithium secondary battery according to Claim 1 ; and an anode positioned opposite the cathode.
Lithium secondary battery according to Claim 9 , wherein the anode comprises an anode current collector and an anode active material layer arranged on a surface of the anode current collector and comprising a silicon-based active material, natural graphite and/or artificial graphite.
Lithium secondary battery according to Claim 9 , wherein the anode comprises an anode current collector and a first anode active material layer and a second anode active material layer stacked successively on a surface of the anode current collector, wherein the first anode active material layer and the second anode active material layer each independently comprise a silicon-based active material, artificial graphite and/or natural graphite, and wherein the content of the silicon-based active material in the first anode active material layer, based on the total weight of the first anode active material layer, is less than the content of the silicon-based active material in the second anode active material layer, based on the total weight of the second anode active material layer.
Lithium secondary battery according to Claim 11 , wherein the content of artificial graphite in the first anode active material layer, based on the total weight of the first anode active material layer, is less than the content of artificial graphite in the second anode active material layer, based on the total weight of the second anode active material layer.
Lithium secondary battery according to Claim 11 , wherein the content of natural graphite in the first anode active material layer, based on the total weight of the first anode active material layer, is greater than the content of natural graphite in the second anode active material layer, based on the total weight of the second anode active material layer.
Lithium secondary battery according to Claim 12 , where the artificial graphite has a crystal orientation index of 1 to 10, as defined by equation 1 below: OI = I 004 / I 110 (in equation 1, OI represents the crystal orientation index, I 004 represents the peak intensity of the (004) plane in the X-ray diffraction pattern (XRD pattern) of the artificial graphite, and I 110 represents the peak intensity of the (110) plane in the XRD pattern of the artificial graphite).

Description

BACKGROUND Technical field The present disclosure relates to a cathode for a lithium secondary battery and a lithium secondary battery comprising the cathode. Technical considerations Secondary batteries are batteries that can be repeatedly charged and discharged. With the development of the information, communication, and display industries, they have been widely used as power sources for portable electronic communication devices, such as camcorders, mobile phones, and laptop PCs. Furthermore, battery packs, including secondary batteries, have recently been developed and used as power sources for environmentally friendly vehicles, such as hybrid vehicles. Examples of secondary batteries include lithium-ion batteries, nickel-cadmium batteries, nickel-hydrogen batteries, and the like. Among them, lithium-ion batteries exhibit a high operating voltage and high energy density per unit weight, making them advantageous in terms of charging speed and weight reduction. For this reason, lithium-ion batteries have been actively developed and deployed in various industrial fields. The lithium secondary battery can, for example, contain an electrode assembly comprising a cathode, an anode, and a separating membrane located between the cathode and the anode, and an electrolyte that impregnates the electrode assembly. The cathode can include a cathode current collector and a cathode active material layer formed on the cathode current collector. For example, the cathode active material layer can contain a cathode active material, a conductive material, a binder, and the like. During repeated charging and discharging of the lithium secondary battery, the cathode can collapse due to the intercalation and deintercalation of lithium ions into and out of the cathode active material. This can result in problems such as gas generation due to side reactions between the lithium metal oxide particles and the electrolyte, and a deterioration of the cycle life characteristics of the lithium secondary battery. Additionally, the problems described above can be more pronounced during repeated fast charging and discharging. SUMMARY A non-restrictive objective of the present disclosure is to provide a cathode for a lithium secondary battery that has improved electrochemical properties. Another non-restrictive objective of the present disclosure is to provide a lithium secondary battery comprising the cathode. A cathode for a lithium secondary battery according to some non-limiting embodiments of the present disclosure comprises: a cathode current collector; and a first cathode active material layer and a second cathode active material layer stacked successively on a surface of the cathode current collector. The first cathode active material layer comprises a first conductive material and either a first cathode active material having a single-particle structure or a mixture of the first cathode active material and a second cathode active material having a secondary-particle structure. The second cathode active material layer comprises a second conductive material and either the second cathode active material or a mixture of the first cathode active material and the second cathode active material. In the first cathode active material layer, the content of the first cathode active material is greater than the content of the second cathode active material, based on the total weight of the first cathode active material layer. In the second cathode active material layer, the content of the second cathode active material is greater than or equal to the content of the first cathode active material, based on the total weight of the second cathode active material layer. The content of the first conductive material in the first cathode active material layer, based on the total weight of the first The content of the second conductive material in the second cathode active material layer is greater than the content of the second conductive material in the second cathode active material layer, based on the total weight of the second cathode active material layer. In some non-restrictive embodiments, the content of the first cathode active material in the first cathode active material layer, based on the total weight of the first cathode active material layer, can be 50 wt.% to 99 wt.%. In some non-restrictive embodiments, the content of the second cathode active material in the first cathode active material layer, based on the total weight of the first cathode active material layer, can be less than 50 wt.%. In some non-restrictive embodiments, the content of the first cathode active material in the second cathode active material layer, based on the total weight of the second cathode active material layer, may be less than 50 wt.%. The content of the second cathode active material in the second cathode active material layer, based on the total weight of the second cathode active material layer, may be 50 wt.% to 99 wt.%. In some non-restrictive embodim