Positive Electrode Active Material with Oriented Li-Ion Diffusion Paths
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Solution Overview
Problem
Conventional lithium secondary battery positive electrode active materials face issues of structural instability and reduced electrochemical performance due to cation mixing, particularly in high-Ni-type materials, leading to rapid deterioration at high and room temperatures, and limited capacity and lifespan.
Innovation Solution
A positive electrode active material with a lithium composite oxide that directs the lithium ion diffusion path to specific crystal planes, such as (012), (101), and (104), and controls grain boundary density to improve electrochemical properties and stability, using a layered lithium composite oxide with controlled calcination processes and a coating layer to enhance structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the Ni content in the positive electrode active material is increased to achieve high discharge capacity, then the battery characteristic such as high discharge capacity is improved, but structural instability occurs due to Li/Ni cation mixing
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Ni content within a specific range (0.5 ≤ Ni < 0.8) rather than using high-Ni materials (Ni ≥ 0.8) that cause severe cation mixing. Additionally, the patent changes the crystal structure parameters by directing lithium ion diffusion paths to specific crystal planes and controlling grain boundary density, thereby achieving high capacity while maintaining structural stability through optimized compositional and structural parameters
Solution Approach 2:
The patent employs composite material strategies by creating a layered lithium composite oxide with specific crystal plane orientations and controlled grain boundary structures. The material combines multiple elements (Li, Ni, Co, Mn, and optional dopants) in a layered structure where the crystal planes are oriented to facilitate lithium ion diffusion while preventing cation mixing, effectively combining high capacity characteristics with structural stability
2Stability of the object's composition
If a single-crystal lithium composite oxide is synthesized by excessively increasing or extending the calcination temperature, then single crystallization is achieved, but cation mixing phenomenon increases
Solution Approach 1:
The patent applies parameter changes by optimizing the calcination temperature and time within specific ranges rather than using excessively high temperatures or extended times. This controlled approach achieves single crystallization while minimizing cation mixing, demonstrating that precise parameter optimization can simultaneously achieve both structural integrity and compositional precision
Solution Approach 2:
The patent applies preliminary action by pre-forming a layered precursor structure before final calcination, and by directing lithium ion diffusion paths to specific crystal planes during the synthesis process. This preliminary structuring ensures that single crystallization occurs with minimal cation mixing, as the crystal framework is already established to guide ion diffusion along desired paths
3Stability of the object's composition
If excessive lithium composite oxides with metastable or rock-salt phase are formed due to increased cation mixing, then single crystallization is achieved, but the deterioration of the positive electrode active material is caused
Solution Approach 1:
The patent applies parameter changes by controlling the calcination conditions (temperature and time) within optimal ranges and by adjusting the composition parameters (Ni content, dopant amounts) to prevent the formation of metastable or rock-salt phases. These parameter optimizations ensure that the material maintains a stable layered structure without deteriorating, achieving both crystallization and long-term stability
Solution Approach 2:
The patent converts the potential harm of cation mixing into a benefit by using controlled, minimal cation mixing during calcination to promote crystal growth and single crystallization, while simultaneously controlling the conditions to prevent excessive mixing that would lead to phase deterioration. The controlled cation mixing actually aids in achieving the desired crystal structure without triggering material degradation
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
The solution enhances lithium ion diffusion capacity and maintains stable charging/discharging performance by reducing grain boundary density and cation mixing, improving high-temperature and room-temperature stability while maintaining high capacity characteristics.
Implementation Method 1
a lithium ion diffusion path in a lithium composite oxide constituting a positive electrode active material is directed to a specific crystal plane
Data Source
AI summary
The present invention relates to a positive electrode active material which is formed such that a lithium ion diffusion path in a lithium composite oxide constituting a positive electrode active material is directed to a specific crystal plane, and has improved electrochemical properties and stability by improving the growth of the crystal plane to which the lithium ion diffusion path is directed, and a lithium secondary battery using the same.