Crystalline Carbon Core Negative Active Material for Lithium Batteries
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Solution Overview
Problem
Conventional negative active materials for lithium rechargeable batteries suffer from poor cycle-life characteristics due to non-uniform particle distribution of metal nanoparticles, leading to increased side reactions with the electrolyte.
Innovation Solution
A negative active material comprising a crystalline carbon core with pores, an amorphous carbon shell, and metal nanoparticles dispersed inside the pores, with specific particle diameter differences to ensure uniform distribution and improved dispersion, reducing direct contact with the electrolyte.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metal nanoparticles are used as negative active material, then high capacity is achieved, but non-uniform particle distribution leads to poor cycle-life characteristics
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core and outer shell have different properties. The crystalline carbon core provides structural stability while the amorphous carbon shell provides uniform lithium insertion/extraction sites. This local differentiation resolves the contradiction by allowing high capacity in the core region while maintaining cycle life through the protective shell region.
Solution Approach 2:
The patent uses composite materials by combining crystalline carbon and amorphous carbon in a core-shell structure. The crystalline carbon core provides high theoretical capacity while the amorphous carbon shell provides structural stability and uniform particle distribution. This composite approach resolves the contradiction between high capacity and good cycle-life characteristics.
2Quantity of substance
If metal nanoparticles are dispersed in carbon matrix, then high capacity is achieved, but increased side reactions with electrolyte occur
Solution Approach 1:
The patent applies the intermediary principle by introducing amorphous carbon as a mediating layer between the metal nanoparticles and the electrolyte. The amorphous carbon shell acts as a protective intermediary that prevents direct contact between the reactive metal nanoparticles and the electrolyte, thereby reducing side reactions while still allowing lithium ion transport for high capacity.
3Reliability
If conventional carbon-based materials are used, then good cycle-life is achieved, but lower energy density results
Solution Approach 1:
The patent resolves this contradiction by creating a composite core-shell structure where the crystalline carbon core provides high theoretical capacity for high energy density, while the amorphous carbon shell provides the structural stability and protection needed for good cycle-life characteristics. This composite approach allows both high energy density and good cycle life to be achieved simultaneously.
Data Source
AI summary
A negative active material for a rechargeable lithium battery includes: a crystalline carbon core including pores; an amorphous carbon shell positioned on the core surface; metal nanoparticles dispersed inside the pores; and amorphous carbon inside the pores, wherein a first particle diameter difference (D50−D10) of the nanoparticles is from about 70 to about 150 nm and the second particle diameter difference (D90−D50) of the nanoparticles is from about 440 to about 520 nm.