Fluorine-Gradient Lithium Composite Oxide for High-Potential Battery Stability
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Solution Overview
Problem
Lithium nickel manganese composite oxide batteries face durability issues due to metal element elution and oxidative decomposition when charged to high potentials, particularly at high temperatures, where increasing fluorine content improves durability but increases battery resistance and degrades Li ion mobility.
Innovation Solution
A lithium composite oxide particle with varying fluorine concentrations between the center and surface layers, where the surface layer has a higher fluorine concentration to suppress metal element elution and oxidative decomposition, and the center layer has a lower fluorine concentration to maintain Li ion diffusibility, thereby balancing durability and input/output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of fluorine is increased to enhance durability and reduce gas generation, then durability is improved, but the interaction between fluorine and charge carrier (Li ions) is increased, degrading Li ion diffusibility and increasing battery resistance
Solution Approach 1:
The patent applies local quality by creating a non-uniform fluorine distribution within the lithium nickel manganese composite oxide particles. The fluorine concentration is specifically controlled to be higher at the particle surface and lower at the particle center, allowing different regions to serve different functions: the fluorine-rich surface suppresses metal element elution and oxidative decomposition, while the fluorine-poor center maintains Li ion diffusibility and low resistance during high-rate charging/discharging.
2Use of energy by moving object
If the positive electrode potential is set to 4.5 V (vs.Li/Li+) or higher to achieve high energy density, then energy density is improved, but metal elements (typically manganese) elute from the positive active material, degrading durability
Solution Approach 1:
The patent applies preliminary anti-action by pre-introducing fluorine atoms into the lithium nickel manganese composite oxide structure before battery operation. This preliminary fluorine incorporation creates stronger binding between anions and cations at the particle surface, forming a protective effect that prevents metal element elution even when the battery operates at high potentials (4.5 V or higher vs. Li/Li+), thus enabling high energy density without sacrificing durability.
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 enhances the battery's durability and input/output characteristics, maintaining high energy density and low resistance even under severe conditions, making it suitable for high-temperature applications like vehicle power sources.
Implementation Method 1
binding of the anions (O, F) and the cations (Ni, Mn) of the lithium nickel manganese composite oxide is increased due to the fluorine
Implementation Method 2
the interaction between the fluorine and a charge carrier (Li ions) is increased, and thus the diffusibility (mobility) of Li ions in the composite oxide is degraded
Implementation Method 3
A fluorine atom concentration Fc (at %) of the particle center portion measured by energy dispersive X-ray spectroscopy
Data Source
AI summary
A positive active material for a lithium-ion secondary battery includes a lithium composite oxide particle containing nickel atoms, manganese atoms, and fluorine atoms. The lithium composite oxide particle includes a particle center portion and a surface layer portion that is closer to a surface of the lithium composite oxide particle than the particle center portion is. A fluorine atom concentration Fc (at %) of the particle center portion measured by energy dispersive X-ray spectroscopy is lower than a fluorine atom concentration Fs (at %) of the surface layer portion.