Graphite Negative Electrode with Holes for Fast Input
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Solution Overview
Problem
Lithium secondary batteries using high-crystallinity graphite for negative electrodes provide high charge and discharge capacity but fail to meet the demand for improved input characteristics, specifically requiring faster input after discharge.
Innovation Solution
A negative electrode carbon material is developed with holes formed in the graphene layer plane of graphite, achieved through an immersion treatment with an alkali aqueous solution followed by a heat treatment, enhancing lithium ion pathways and improving input characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-crystallinity graphite is used as negative electrode active material, then charge and discharge capacity is improved, but input characteristic deteriorates
Solution Approach 1:
The patent applies porous materials by forming holes in the graphene layer plane of graphite through chemical treatment with alkali solution followed by heat treatment. These pores create additional pathways for lithium ion transport, enabling faster ion diffusion throughout the graphite structure while preserving the high capacity benefits of crystalline graphite. The porous structure resolves the contradiction by providing both high capacity (through intact graphite crystallinity) and fast input characteristics (through enhanced ion pathways).
Solution Approach 2:
The patent changes the structural parameters of graphite by introducing holes into the graphene layers through controlled chemical etching and heat treatment. This parameter change modifies the diffusion pathways for lithium ions without fundamentally altering the graphite's crystalline structure or capacity. The holes increase the surface area and create shortcuts for ion transport, thereby improving input characteristics while maintaining high charge and discharge capacity.
2Speed
If graphite structure is modified to improve input characteristic, then lithium ion pathways are enhanced, but structural integrity may deteriorate
Solution Approach 1:
The controlled formation of pores through chemical treatment and heat treatment creates a stable porous graphite structure. The pores are formed in a controlled manner that maintains the overall structural integrity of the graphite crystallites. The heat treatment step specifically stabilizes the structure by graphitizing the edges and reinforcing the walls between pores, ensuring that the enhanced lithium ion pathways do not compromise structural stability.
Solution Approach 2:
The treatment process creates a composite structure within the graphite, combining intact crystalline regions with controlled porous pathways. The graphite maintains its fundamental crystalline structure for stability while incorporating porous features for enhanced ion transport. This composite architecture allows simultaneous achievement of fast lithium ion pathways and structural stability.
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 modified graphite-based material significantly enhances the input characteristic of lithium secondary batteries by increasing lithium ion pathways, leading to improved charge and discharge efficiency and capacity.
Implementation Method 1
subjecting a graphite to an immersion treatment with an alkali aqueous solution containing an alkaline metal or an alkaline earth metal
Implementation Method 2
thereafter subjecting the graphite to a heat treatment to form the holes
Data Source
AI summary
There is provided a negative electrode carbon material for a lithium secondary battery, including a graphite-based material in which holes are formed in a graphene layer plane.