Negative Active Material for Lithium Battery
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving excellent charge and discharge rate characteristics due to limitations in the negative active material's structure and composition, leading to suboptimal performance in high-rate charge and discharge processes.
Innovation Solution
A negative active material for rechargeable lithium batteries is developed, comprising a secondary particle with a core of agglomerated primary natural graphite particles coated with amorphous carbon, featuring a specific Raman peak intensity ratio and lattice constant, which enhances charge and discharge rate characteristics by minimizing side reactions and maintaining a dense internal structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional negative active materials are used, then the battery can operate, but the charge and discharge rate characteristics are suboptimal
Solution Approach 1:
The patent optimizes specific parameters of the negative active material including the Raman peak intensity ratio (ID/ID′) of the amorphous carbon coating layer to 1.8-2.5 and lattice constant La to 30-45 nm. These parameter changes improve both charge/discharge rate characteristics and cycling stability by controlling the material's structural properties at the nanoscale level.
Solution Approach 2:
The patent employs a composite structure consisting of amorphous carbon coating layer on natural graphite particles. This composite material combines the high capacity of natural graphite with the conductivity and structural stability of amorphous carbon, achieving both high charge/discharge rates and excellent cycling characteristics.
2Ease of manufacture
If the negative active material structure is simplified, then manufacturing is easier, but charge and discharge rate characteristics deteriorate
Solution Approach 1:
The patent specifies precise parameter ranges for the negative active material (Raman ID/ID′ ratio of 1.8-2.5, lattice constant La of 30-45 nm) that can be achieved through controlled carbonization processes. These parameter specifications provide clear manufacturing targets while maintaining excellent charge rate characteristics, balancing ease of manufacture with performance requirements.
3Stability of the object's composition
If the lattice constant La is increased beyond 45 nm, then the internal structure becomes less dense, but charge and discharge rate characteristics worsen
Solution Approach 1:
The patent identifies and optimizes the lattice constant La to a specific range of 30-45 nm, which maintains appropriate internal structure density while enabling excellent discharge rate characteristics. This parameter optimization ensures that the material structure supports both structural stability and high-rate performance.
Data Source
AI summary
A rechargeable lithium battery includes a negative active material including: a secondary particle including a core in which a plurality of primary particles are agglomerated, the primary particles including a natural graphite; and a coating layer including amorphous carbon and surrounding the core, wherein a Raman peak intensity ratio of a D peak (1350 cm−1 to 1370 cm−1) to a D′ peak (1570 cm−1 to 1620 cm−1) (ID/ID′) of the negative active material is about 3.2 to about 3.8, and a lattice constant La of the negative active material is about 30 nm to about 45 nm.