Cathode Active Material with Directed Li-Ion Diffusion Paths
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Solution Overview
Problem
Current lithium secondary battery cathode active materials face challenges with poor thermal stability, lifespan performance, and low energy density, particularly in layered type materials like LiNiO2 and Li-Ni-Mn-Co-based composite oxides, which suffer from structural instability and interface issues that degrade battery performance over time.
Innovation Solution
A cathode active material with a rhombohedral crystal structure and secondary particles formed by aggregated primary particles, where the lithium ion diffusion path is directed towards the center, forming a one-dimensional or two-dimensional tunnel structure, enhancing lithium ion conductivity and structural stability, and maintaining a constant transition metal concentration across the particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LiNiO2 or Li-Ni-Mn-Co-based composite oxide is used as cathode active material, then high capacity can be achieved, but thermal stability and lifespan performance deteriorate due to structural instability
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of transition metals within the cathode active material particles. The inner layer contains a different metal composition compared to the outer layer, with the transition metal concentration varying radially. This local compositional variation allows the inner region to provide high capacity while the outer region maintains structural stability and thermal resistance, thereby resolving the contradiction between achieving high capacity and maintaining reliability.
2Reliability
If substitution of nickel with transition metal elements is performed, then thermal stability improves, but lifespan performance remains insufficient
Solution Approach 1:
The patent employs parameter changes by systematically varying the transition metal concentration as a function of radial distance from the particle center. The concentration gradient parameter is optimized to achieve both thermal stability and long lifespan. Specifically, the transition metal concentration is higher at the outer regions for thermal stability and lower at the inner regions for maintaining capacity and lifespan, creating an optimal balance that resolves the contradiction between thermal stability and lifespan performance.
3Adaptability or versatility
If uniform dispersion of Mn and Ni compounds is created to form solid solution, then new concept cathode material is achieved, but interface resistance lowers output and deteriorates lifespan
Solution Approach 1:
The patent applies segmentation by dividing the cathode active material particles into distinct regions: an inner layer and an outer layer, separated by an interface. This segmentation allows different metal compositions in each layer, preventing the formation of a uniform solid solution throughout. The interface between layers is designed to minimize resistance, enabling efficient ion transport while maintaining compositional flexibility. This segmented structure resolves the contradiction between material composition flexibility and performance by allowing optimized compositions in each region without creating harmful interface resistance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration improves lithium ion conduction velocity, cycle characteristics, and internal battery impedance, leading to enhanced capacity and lifespan characteristics by facilitating efficient lithium storage and release during charging and discharging.
Implementation Method 1
a lithium ion diffusion path in the primary particles and a lithium ion diffusion path in the secondary particles which is directed toward a center direction of the entire particles
Data Source
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AI summary
The present invention relates to a cathode active material for lithium secondary battery and a lithium secondary battery including the same, and more specifically it relates to an cathode active material for lithium secondary battery in which the a lithium ion diffusion path in the primary particles is formed to exhibit specific directivity, and a lithium secondary battery including the same. The cathode active material for lithium secondary battery of the present invention has a lithium ion diffusion path exhibiting specific directivity in the primary particles and the secondary particles, thus not only the conduction velocity of the lithium ion is fast and the lithium ion conductivity is high but also the cycle characteristics are improved as the crystal structure hardly collapses despite repeated charging and discharging.