Graphite Anode Composition With Pore-Filled Amorphous Carbon
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Solution Overview
Problem
Current rechargeable lithium batteries face challenges in achieving good safety and cycle-life characteristics due to limitations in negative active materials, particularly in terms of internal density, expansion during charge and discharge, and side reactions with the electrolyte.
Innovation Solution
A negative active material is developed comprising agglomerated natural graphite primary particles with pores and amorphous carbon, where the amorphous carbon occupies 10% to 30% of the cross-sectional area, and is prepared through a method involving mixing with an amorphous carbon precursor, controlling pressure, and heat-treating to enhance internal density and reduce side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If natural graphite is used as negative active material, then intercalation and deintercalation of lithium ions is achieved, but internal density is insufficient and expansion occurs during charge and discharge
Solution Approach 1:
The patent uses composite materials by combining natural graphite primary particles with amorphous carbon and pores to form secondary particles. This composite structure increases internal density while the porous design accommodates expansion during charge-discharge cycles, resolving the contradiction between density and stability.
Solution Approach 2:
The patent introduces pores within the secondary particle structure to accommodate volume expansion of graphite during lithium intercalation. The pores act as buffer spaces that prevent structural degradation, thereby improving cycle-life characteristics while maintaining high internal density.
2Reliability
If natural graphite is used as negative active material, then lithium ion intercalation is achieved, but side reactions with electrolyte increase
Solution Approach 1:
The patent applies local quality by creating regions with different properties within the secondary particle. The amorphous carbon provides a stable interface with electrolyte that reduces side reactions, while the natural graphite core maintains high lithium capacity. This local differentiation resolves the contradiction between reliability and harmful factors.
Solution Approach 2:
The amorphous carbon acts as an intermediary layer between the natural graphite and the electrolyte. This intermediate material reduces direct contact between graphite and electrolyte, thereby minimizing side reactions while still allowing efficient lithium ion transport.
3Productivity
If amorphous carbon is added to increase internal density, then charge and discharge rate characteristics improve, but the area percentage must be controlled to minimize side reactions
Solution Approach 1:
The patent optimizes the area percentage of amorphous carbon to 10-30% to achieve the best balance between charge-discharge rate characteristics and minimization of side reactions. This parameter optimization resolves the contradiction by finding the optimal concentration of amorphous carbon that provides both high productivity and low harmful factors.
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 results in improved charge and discharge rate characteristics, increased internal density, and extended cycle life by minimizing expansion and side reactions, thus enhancing the overall performance and efficiency of the lithium battery.
Implementation Method 1
maintaining the resulting product at a temperature at which a viscosity of the amorphous carbon precursor is about 100 cP to about 1000 cP
Implementation Method 2
controlling a pressure of the mixture
Implementation Method 3
heat-treating the resulting material
Data Source
AI summary
A negative active material for a rechargeable lithium battery includes a secondary particle in which a plurality of natural graphite primary particles are agglomerated, the plurality of primary particles including natural graphite, and the secondary particle including pores, and an amorphous carbon positioned in the pores, wherein an area of the amorphous carbon is about 10% to about 30% based on a total area of 100% of the negative active material, in a cross-section of the negative active material.