Dual-Layer Battery Electrode Binder Layout for Flexibility and Adhesion
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Solution Overview
Problem
Existing electrodes for lithium secondary batteries face challenges in achieving both strong adhesion to the current collector and flexibility, particularly in applications requiring repeated bending, such as wearable devices, due to the use of small particle diameters and the addition of soft materials that can degrade coating productivity or increase electrode thickness, reducing energy density.
Innovation Solution
The electrode is designed with a dual-layer structure, where the lower layer lacks a rubbery binder and includes a first active material and a non-rubbery binder, while the upper layer incorporates a rubbery hydrogenated nitrile butadiene rubber (H-NBR) and a non-rubbery binder, both based on polyvinylidene fluoride (PVDF)-polymers, with specific weight ratios to enhance adhesion and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a soft material is added as a binder to improve electrode flexibility, then flexibility is improved, but solid content of slurry is reduced causing degradation of coating productivity
Solution Approach 1:
The patent applies different binder compositions to different regions of the electrode active material layer. The lower layer region (near current collector) uses no rubbery binder for strong adhesion, while the upper layer region uses rubbery binder for flexibility. This local differentiation allows each region to optimize its properties without compromising the other.
Solution Approach 2:
The electrode active material layer is divided into two distinct layers: a lower layer region adjacent to the current collector and an upper layer region above it. Each layer has different binder compositions tailored to its specific function - the lower layer for adhesion and the upper layer for flexibility.
2Ease of operation
If a soft material is added as a binder to improve electrode flexibility, then flexibility is improved, but electrode thickness increases resulting in decrease in energy density
Solution Approach 1:
The rubbery binder is localized only in the upper layer region where flexibility is needed, while the lower layer region uses only non-rubbery binder. This spatial distribution minimizes the total amount of soft material required, reducing thickness and weight while maintaining flexibility where needed.
Solution Approach 2:
By segmenting the binder composition into region-specific formulations, the patent reduces the overall quantity of rubbery binder needed compared to a homogeneous composition, thereby minimizing the increase in electrode thickness and weight.
3Reliability
If an active material with small particle diameter is used to ensure electrode performance, then electrode performance is improved, but adhesion to current collector is reduced
Solution Approach 1:
The lower layer region uses a binder composition optimized for adhesion (no rubbery binder) to ensure small particle active material adheres strongly to the current collector, while the upper layer uses rubbery binder for flexibility.
Solution Approach 2:
The patent uses a composite binder system with different compositions in different layers. The lower layer uses a non-rubbery binder composite for adhesion, while the upper layer uses a rubbery binder composite for flexibility, creating a multi-functional electrode structure.
Data Source
AI summary
Disclosed is an electrode including: a current collector; and an electrode active material layer disposed on at least one surface of the current collector, wherein the electrode active material layer includes a lower layer region facing the current collector, and an upper layer region facing the lower layer region and extended to the surface of the electrode active material layer, the lower layer region includes a first active material and a first non-rubbery binder and is free from a rubbery binder, the upper layer region includes a second active material, a second non-rubbery binder and a rubbery binder, the rubbery binder is a hydrogenated nitrile butadiene rubber (H-NBR), each of the first non-rubbery binder and the second non-rubbery binder includes a polyvinylidene fluoride (PVDF)-based polymer, and the weight ratio of the second non-rubbery binder to the rubbery binder in the upper layer region is 1:0.03-1:0.07. Also disclosed are a method for manufacturing the electrode and a lithium secondary battery including the electrode.