Carbon-Rich Negative Electrode Adhesive for Longer Cycle Life
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving good interface adherence between the current collector and the active material layer, which affects the cycle-life characteristics of the battery.
Innovation Solution
A negative electrode design is introduced, featuring a current collector, a negative active material layer, and an adhesive layer with a carbon-based material composition, ensuring an interface adhesion force of 5 gf/mm or more between the adhesive layer and the current collector or the negative active material layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional adhesive layer is used between the current collector and negative active material layer, then the battery can be assembled, but the interface adherence is insufficient leading to poor cycle-life characteristics
Solution Approach 1:
The patent changes the compositional parameters of the adhesive layer by specifying that it contains carbon-based material at 90 wt% or more based on the total weight of the adhesive layer. This parameter change (composition ratio) directly improves the interface adherence strength to 5 gf/mm or more, which in turn enhances the cycle-life characteristics of the battery.
Solution Approach 2:
The adhesive layer is designed as a composite material primarily composed of carbon-based material (90 wt% or more) combined with specific binders (carboxymethyl cellulose and styrene-butadiene rubber in a weight ratio of 1:0.1 to 1:1). This composite structure provides both strong adhesion to the current collector and negative active material layer while maintaining flexibility and electrochemical stability, thereby improving interface adherence and cycle-life characteristics.
2Strength
If the adhesive layer thickness is increased to improve adhesion, then interface adherence may improve, but the energy density and battery performance deteriorate
Solution Approach 1:
The patent optimizes the thickness parameter of the adhesive layer to 30 μm or less, which is sufficiently thin to maintain high energy density while still achieving the required interface adherence strength of 5 gf/mm or more through the optimized carbon-based material composition (90 wt% or more). This parameter optimization resolves the contradiction between adhesion strength and energy density.
Solution Approach 2:
The adhesive layer is designed with localized high carbon-based material content (90 wt% or more) specifically at the interface regions where adhesion is needed, while maintaining overall thinness (30 μm or less). This local quality enhancement ensures strong interface adherence without unnecessarily increasing the overall layer thickness that would reduce energy density.
Data Source
AI summary
Disclosed are a negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same. The negative electrode includes a current collector; a negative active material layer, and an adhesive layer between the current collector and the negative active material and having a thickness of about 30 μm or less, wherein the adhesive layer comprises a carbon-based material at an amount of about 90 wt % or more based on the total 100 wt % of the adhesive layer.