Multi-Layered Cathode Structure for Lithium Battery Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high energy density and long-term stability due to cracking of cathode active materials during the pressing process, which can lead to side reactions with the electrolyte and degrade thermal stability and life-span.
Innovation Solution
A cathode for lithium secondary batteries is designed with a multi-layered structure comprising a first cathode active material layer with a secondary particle structure and a second layer with a single particle shape, both containing lithium metal oxides with specific compositions and particle size distributions, to enhance mechanical and electrical stability and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a pressing process is performed to obtain high energy density, then energy density is improved, but cracks are generated in the cathode active material leading to degraded life-span and thermal stability
Solution Approach 1:
The cathode active material is divided into a composite structure consisting of a first cathode active material (high nickel content, 60-80 mol%) providing high capacity and a second cathode active material (lower nickel content, 30-50 mol%) forming a coating layer that provides structural stability. This segmentation allows the high-energy-density material to be protected by a stabilizing outer layer, preventing crack generation during pressing while maintaining high energy density.
Solution Approach 2:
The invention uses a composite cathode active material structure where two different cathode active materials are combined: a high-nickel material (LiNi0.8Co0.1Mn0.1O2) for high capacity and a modified nickel oxide material (LiNi0.4Co0.2Mn0.4O2) for structural stability. The composite structure enables both high energy density and improved reliability by distributing mechanical stress and preventing crack propagation through the interface between the two materials.
2Quantity of substance
If nickel content is increased to improve capacity, then capacity is improved, but thermal stability and structural integrity are degraded
Solution Approach 1:
The cathode active material exhibits local quality variation through its composite structure: the inner core region contains high nickel content (60-80 mol%) for high capacity, while the outer coating layer contains lower nickel content (30-50 mol%) for enhanced thermal stability and structural integrity. This spatial distribution of different nickel concentrations optimizes both capacity and strength locally throughout the material structure.
Data Source
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AI summary
A cathode for a lithium secondary battery includes a cathode current collector, a first cathode active material layer including a first cathode active material particle, and a second cathode active material layer including a second cathode active material particle. The first cathode active material layer and the second cathode active material layer are sequentially stacked from the cathode current collector. The first cathode active material particle and the second cathode active material particle have different compositions or particle structures from each other. The first cathode active material particle and the second cathode active material particle include lithium metal oxides containing nickel. The second cathode active material particle has a single particle shape and has a particle size distribution satisfying a specific range relation.