Graphite-Anode Composition With Internal Amorphous Carbon Stability
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high energy density, high capacity, and stability due to issues with negative electrode active materials, particularly related to amorphous carbon exposure causing side reactions and poor bonding strength.
Innovation Solution
A negative electrode active material comprising graphite with secondary particles containing amorphous carbon inside, where the ratio of amorphous carbon to primary particle diameter is 0.1 to 0.5, enhancing lithium ion bridging and suppressing side reactions while improving manufacturing processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If amorphous carbon is added to negative electrode active material to improve capacity, then energy density increases, but side reactions occur causing stability deterioration
Solution Approach 1:
The patent embeds amorphous carbon particles inside the hollow interior of spherical graphite particles, creating a nested structure where the inner amorphous carbon is protected by the outer graphite shell. This prevents direct exposure of amorphous carbon to electrolyte, suppressing side reactions while maintaining high capacity contribution from the amorphous carbon core.
Solution Approach 2:
The patent creates a heterogeneous structure where different regions have different properties: the outer shell is crystalline graphite with low reactivity, while the inner core is amorphous carbon with high capacity. This local differentiation allows the amorphous carbon to contribute to energy density without suffering from its inherent instability when exposed.
2Quantity of substance
If hard carbon is used in negative electrode to increase capacity, then energy density improves, but bonding strength decreases due to poor adhesion
Solution Approach 1:
The hard carbon (amorphous carbon) is nested inside the hollow sphere of graphite, which acts as a protective shell. This nested structure provides mechanical support and improves bonding strength, while the inner hard carbon core maintains high capacity characteristics.
Solution Approach 2:
The patent creates a composite material system combining crystalline graphite and amorphous carbon in a specific architecture. The graphite shell provides structural integrity and bonding strength, while the amorphous carbon core provides high capacity, achieving synergistic effects.
3Quantity of substance
If negative electrode active material is optimized for high capacity, then energy density increases, but manufacturing processability deteriorates due to inappropriate slurry viscosity
Solution Approach 1:
The patent optimizes the particle size parameters of both the outer graphite shell and inner amorphous carbon core, controlling their size ratios and distributions to achieve appropriate slurry viscosity. This allows high-capacity materials to be processed with standard manufacturing parameters, improving ease of manufacture.
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 solution provides a boost charging effect, improved bonding strength, and reduced side reactions, leading to enhanced battery efficiency and longevity.
Implementation Method 1
amorphous carbon present inside the secondary particles... improving processability in manufacturing a negative electrode by providing a slurry having appropriate viscosity
Implementation Method 2
generates electrical energy by oxidation and reduction reactions when lithium ions are intercalated/deintercalated into/from the positive electrode and the negative electrode
Data Source
AI summary
The present invention relates to a negative electrode active material for a rechargeable lithium battery and a rechargeable lithium battery including the same, and the negative electrode active material for a rechargeable lithium battery includes graphite including secondary particles in which primary particles are assembled; and amorphous carbon present inside the secondary particles, wherein a ratio of the average particle diameter D50 of the amorphous carbon to the average particle diameter D50 of the primary particles is 0.1 to 0.5.