Graphene-Coated Li-Ion Cathode Particles for Rate Characteristics
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in achieving further improvements in rate characteristics as their use becomes more widespread, despite existing techniques for decreasing internal resistance and enhancing electronic conductivity of positive electrode active materials.
Innovation Solution
A positive electrode active material is developed with active particles containing Li and a transition metal, coated with a layer of graphene or multilayer graphene, where the Raman spectrum exhibits specific intensity ratios of G, D, and 2D bands, enhancing conductivity and adhesion, thereby improving rate characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conductive material coating is applied to positive electrode active material particles, then internal resistance decreases and electronic conductivity improves, but rate characteristics cannot be sufficiently enhanced
Solution Approach 1:
The patent changes the chemical composition and structural parameters of the coating material from conventional conductive materials to graphene-specific structures, characterized by specific Raman spectrum parameters (ID/G ratio, 2D band intensity) that indicate optimal graphene quality and layer structure, thereby achieving superior electronic conductivity and rate characteristics
Solution Approach 2:
The patent creates a composite structure where graphene coating layers are applied to positive electrode active material particles (such as LiCoO2, LiMn2O4, or LiNi0.8Co0.1Mn0.1O2), forming a heterogeneous composite that combines the electrochemical activity of the metal oxide core with the exceptional electronic conductivity and structural stability of the graphene shell
2Reliability
If graphene coating is applied to enhance conductivity, then electronic conductivity increases, but coating adhesion and stability must be maintained
Solution Approach 1:
The patent optimizes coating parameters including graphene layer thickness, crystallinity (indicated by Raman ID/G ratio), and layer structure (indicated by 2D band intensity) to achieve the optimal balance between electronic conductivity and adhesion stability, ensuring the coating remains firmly attached while providing superior conductive pathways
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 use of graphene or multilayer graphene coating on active material particles significantly increases electronic conductivity and adhesion, leading to enhanced rate characteristics and stability in lithium ion secondary batteries, improving both performance and fabrication stability.
Implementation Method 1
The coating layer has a Raman spectrum with a G band (a peak of 1530 cm−1 to 1630 cm−1), a D band (a peak of 1300 cm−1 to 1400 cm−1), and a 2D band (a peak of 2650 cm−1 to 2750 cm−1). At least the intensity of the 2D band normalized by the intensity of the G band (2Dint/Gint) satisfies 0.05≤2Dint/Gint.
Data Source
AI summary
A positive electrode active material for lithium ion secondary battery includes: active material particles including one or more compounds including Li and a transition metal; and a coating layer coating at least a part of a surface of the active material particles. The coating layer includes at least one of graphene or multilayer graphene The coating layer has a Raman spectrum with a G band (a peak of 1530 cm−1 to 1630 cm−1), a D band (a peak of 1300 cm−1 to 1400 cm−1), and a 2D band (a peak of 2650 cm−1 to 2750 cm−1). At least the intensity of the 2D band normalized by the intensity of the G band (2Dint/Gint) satisfies 0.05≤2Dint/Gint.