Negative Electrode Amorphous Carbon Optimization
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Solution Overview
Problem
The existing negative electrodes for lithium ion secondary batteries face challenges in durability and gas generation during charging, particularly when graphite is covered with excessive amorphous carbon, leading to separation issues from the current collector.
Innovation Solution
A negative electrode with a carbon material comprising graphite particles covered with amorphous carbon by 5 wt % or less, combined with an aqueous binder, enhances the adhesive power and durability by optimizing the ratio of amorphous carbon to graphite, thereby improving the battery's output and lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If graphite is covered with amorphous carbon to suppress gas generation during charging, then gas generation is suppressed, but the negative electrode active material layer separates from the current collector
Solution Approach 1:
The invention changes the quantitative parameter of amorphous carbon coverage from excessive coverage to 5 wt% or less relative to total carbon material weight. This parameter optimization maintains sufficient gas suppression while preventing the separation issue caused by excessive amorphous carbon coverage.
Solution Approach 2:
The invention uses a composite carbon material consisting of graphite particles combined with amorphous carbon in a specific ratio (5 wt% or less). This composite structure combines the benefits of graphite (high capacity, stable structure) with minimal amorphous carbon coverage (gas suppression) while avoiding the harmful effects of excessive amorphous carbon.
2Power
If graphite is covered with amorphous carbon to improve output characteristic, then output characteristic is improved, but durability decreases due to separation from current collector
Solution Approach 1:
The invention optimizes the amorphous carbon content parameter to 5 wt% or less, which is sufficient to improve output characteristic through enhanced conductivity and surface properties, while being low enough to prevent separation and ensure long-term durability.
3Object-generated harmful factors
If excessive amorphous carbon is used to cover graphite, then gas generation is suppressed, but adhesive power between active material layer and current collector decreases
Solution Approach 1:
The invention precisely controls the amorphous carbon parameter at 5 wt% or less, which maintains adequate gas suppression capability while preserving strong adhesive bonding between the active material layer and current collector by avoiding excessive amorphous carbon accumulation.
Data Source
AI summary
A negative electrode for a lithium ion secondary battery includes: a negative electrode current collector (11); and a negative electrode active material for a lithium ion secondary battery, which is disposed on the negative electrode current collector and contains a carbon material and an aqueous binder. The carbon material is a graphite particle having a covering layer containing amorphous carbon by 5 wt % or less relative to a total weight of the carbon material.