Layered Cathode Material Surface Chemistry for Lower Lithium Elution
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Solution Overview
Problem
Conventional lithium secondary batteries face challenges in reducing the amount of alkaline lithium compound elution and improving cycle characteristics, which affects their performance and durability.
Innovation Solution
A positive electrode active material with a layered structure containing Li, carbon, and sulfur, where specific abundance ratios of sulfur, carbon, lithium, and other elements are optimized to reduce alkaline lithium compound elution and enhance cycle characteristics, using a combination of X-ray photoelectron spectroscopy (XPS) measurements and controlled molar ratios to ensure appropriate surface composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional positive electrode active materials are used, then the battery can operate, but the amount of alkaline lithium compound elution is high and cycle characteristics are poor
Solution Approach 1:
The patent applies local quality by creating a surface-modified positive electrode active material where the surface layer has different composition and properties from the bulk material. Specifically, sulfur-containing compounds are attached to the surface of primary particles, creating a surface layer with reduced alkaline lithium compound elution while maintaining the electroactive bulk composition for good cycle characteristics.
Solution Approach 2:
The patent uses composite materials by combining lithium metal composite oxide particles with sulfur-containing compounds on the surface. This creates a composite structure where the core material provides electrochemical activity and the surface sulfur-containing layer provides protection against alkaline lithium compound elution, thereby improving both reliability and reducing harmful factors.
2Object-generated harmful factors
If sulfur-containing compounds are attached to the surface, then alkaline lithium compound elution is reduced, but the surface composition must be precisely controlled
Solution Approach 1:
The patent applies parameter changes by precisely controlling the sulfur-to-metal molar ratio parameter in the range of 0.001 to 0.005. This specific parameter range ensures that enough sulfur-containing compounds are present on the surface to reduce alkaline lithium compound elution, while avoiding excessive sulfur that would create manufacturing difficulties and composition control issues.
3Object-generated harmful factors
If the sulfur content is increased to reduce elution, then alkaline lithium compound elution decreases, but the electrochemical performance may be affected
Solution Approach 1:
The patent applies parameter changes by optimizing the sulfur-to-metal molar ratio to fall within the specific range of 0.001 to 0.005. This parameter optimization ensures that the sulfur content is sufficient to reduce alkaline lithium compound elution while remaining low enough to maintain good electrochemical performance and cycle characteristics.
Solution Approach 2:
The patent applies local quality by concentrating sulfur-containing compounds specifically on the surface of primary particles rather than uniformly throughout the bulk material. This localized surface modification allows the sulfur to effectively reduce alkaline lithium compound elution from the surface while minimizing its impact on the overall electrochemical performance determined by the bulk material composition.
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 optimized composition reduces the amount of alkaline lithium compound elution and improves the cycle characteristics of lithium secondary batteries, leading to enhanced performance and durability.
Implementation Method 1
XPS(S) represents an abundance ratio [at %] of the sulfur element determined from a S2p spectrum measured by X-ray photoelectron spectroscopy
Data Source
AI summary
A positive electrode active material for a lithium secondary battery that can reduce the amount of the lithium compound to be eluted and improve the cycle characteristic of the lithium secondary battery is achieved. According to an embodiment of the present invention, the positive electrode active material for a lithium secondary battery has a layered structure, contains Li, the carbon element, and the sulfur element, and satisfies 0.11≤XPS(S)/XPS(C)≤1.50. XPS(S) and XPS(C) respectively represent the abundance ratios of the sulfur element and the carbon element measured by XPS.