Multi-Layer Electrode Coating for Low-DCIR Li-Ion Cells
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Solution Overview
Problem
Lithium-ion battery cells face challenges in maximizing energy density while minimizing direct current internal resistance (DCIR) due to issues with adhesion of electrodes to current collectors, leading to delamination and reduced cycle life.
Innovation Solution
A multi-layered coated electrode design with a current collector coated on both sides, featuring a first coating layer with a higher binder and conductive additive content than a second layer, applied in a 'wet-on-wet' technique to enhance adhesion and conductivity, and a bimodal particle size distribution to increase calendering density and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the amount of binder in the coating is reduced to improve power and rate capabilities by lowering DCIR, then DCIR decreases and power capability improves, but adhesion of the coating to the current collector deteriorates, resulting in delamination
Solution Approach 1:
The single coating layer is segmented into multiple coating layers with different compositions. The first coating layer (closer to current collector) has higher binder content for adhesion, while the second coating layer (outer layer) has lower binder content for reduced DCIR and improved power capability. This segmentation allows each layer to optimize for its specific function.
Solution Approach 2:
Different regions of the coating (first vs. second coating layers) are assigned different local qualities - the first layer has higher binder concentration for adhesion at the current collector interface, while the second layer has lower binder concentration for reduced electrical resistance. This local quality differentiation resolves the contradiction between adhesion and conductivity.
2Power
If the amount of conductive additive is increased proportionally to reduce DCIR, then DCIR decreases and charging capability improves, but the amount of active material that can be included decreases, reducing energy density
Solution Approach 1:
The coating is segmented into layers with different functional priorities. The first coating layer near the current collector contains higher conductive additive for electron transport and lower DCIR. The second outer coating layer contains more active material for energy storage. This segmentation allows conductive additives to be concentrated where needed for charging capability while preserving energy density.
Solution Approach 2:
Conductive additive concentration is optimized locally - higher in the first coating layer where electrical conductivity is critical for reducing DCIR, and lower in the second coating layer where active material content is prioritized for energy density. This local optimization resolves the contradiction between charging capability and energy density.
3Quantity of substance
If the coating weight on the current collector is increased to maximize energy density, then energy density increases, but DCIR increases due to slower kinetics
Solution Approach 1:
The thick coating is segmented into multiple layers. The first coating layer (thinner) near the current collector has optimized composition for electrical conductivity with higher conductive additive and binder, reducing DCIR. The second coating layer (thicker) outer layer contains more active material to maximize energy density. This segmentation allows the overall coating weight to be high for energy density while maintaining good electrical conductivity.
Solution Approach 2:
The coating composition varies locally through the layers - the first layer has properties optimized for electrical conductivity (higher conductive additive) to reduce DCIR, while the second layer has properties optimized for energy storage (higher active material). This local quality gradient allows simultaneous optimization of both energy density and power capability.
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 reduces DCIR, improves adhesion, and enhances energy density by optimizing the distribution of binder and conductive additives, thereby extending cycle life and charging capabilities of lithium-ion battery cells.
Implementation Method 1
a multi-layered coated electrode is provided which includes a current collector coated with at least two coating layers on each of two opposing surfaces of the current collector
Data Source
AI summary
Systems and methods are provided for an electrode for a lithium-ion battery cell. In one example, the electrode may include a current collector having two opposing sides, at least one of the two opposing sides being configured with a first coating layer disposed on the current collector at a first loading, where the first coating layer may include a first binder in a first weight ratio, and a second coating layer disposed on the first coating layer at a second loading, where the second coating layer may include a second binder in a second weight ratio, wherein the first weight ratio may be greater than the second weight ratio, and a ratio of the first loading to the second loading may be less than 1:2. In this way, direct current internal resistance of the lithium-ion battery cell may be decreased while maintaining or increasing adhesion within the electrode.