Dual-Layer Negative Electrode Plate for Fast-Charging Stability
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Solution Overview
Problem
Lithium ion batteries face issues with lithium precipitation, electrolyte drying, and temperature rise during fast charging, leading to structural instability and reduced performance.
Innovation Solution
A negative electrode plate design with two active material layers, where the bottom layer uses a binder with low solubility parameter to prevent swelling and maintain mechanical strength, and the top layer uses a binder with high solubility parameter for better electrolyte affinity and lithium ion conduction, enhancing interface bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a binder with high affinity to electrolyte is used to improve fast charging capacity, then electrolyte infiltration and lithium ion conduction are enhanced, but the binder swells and bonds poorly to the active material, reducing mechanical stability
Solution Approach 1:
The patent divides the negative electrode plate into multiple layers with different binder types. The first binder layer (closer to current collector) uses a binder with lower electrolyte affinity for structural stability, while the second binder layer (outer layer) uses a binder with higher electrolyte affinity for fast charging performance. This segmentation allows each layer to perform its specific function without compromising the other.
Solution Approach 2:
Different regions of the negative electrode plate are assigned different binder properties. The inner region near the current collector uses binders optimized for mechanical stability and strong bonding, while the outer region in contact with electrolyte uses binders optimized for electrolyte infiltration and lithium ion conduction. This local differentiation resolves the contradiction between stability and fast charging capacity.
2Productivity
If fast charging graphite is used in the upper layer to improve ion transmission, then fast charging capacity increases, but energy density decreases due to lower capacity compared to highly compacted graphite
Solution Approach 1:
The negative active material layer is segmented into multiple layers with different graphite types. The lower layer uses highly compacted graphite for high capacity and energy density, while the upper layer uses fast charging graphite for rapid ion transmission. This segmentation allows the electrode to achieve both high energy density and fast charging capacity by combining different graphite materials in strategic positions.
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 design ensures stable adhesion of the active material layers, improves mechanical strength, and balances energy density and fast charging capacity, reducing lithium precipitation and electrolyte swelling, thereby extending cycle life and reducing expansion.
Implementation Method 1
a first binder with a solubility parameter difference of ≥4(J·cm−3)1/2 from the electrolyte to prevent swelling and ensure strong bonding
Implementation Method 2
a second binder with a solubility parameter difference ≤5(J·cm−3)1/2 for better affinity and electrolyte infiltration, enhancing mechanical strength and lithium ion conduction
Data Source
AI summary
Disclosed are a negative electrode plate and a battery. A first negative active material layer is disposed at a bottom layer, and includes a first binder resistant to electrolyte swelling, has a better chemical corrosion resistance, and is not easy to age, so as to ensure long-term bonding, and reduce battery cell expansio. The negative electrode plate can maintain good mechanical strength and elongation at immersion of the electrolyte, so as to ensure that it is not separatedr. A second binder in a second negative active material layer away from the negative current collector uses a high swelling material, the high-swelling binder is in good affinity with the electrolyte, and the electrolyte infiltration speed is good, which facilitates lithium ion conduction. Furthermore, the high-swelling binder is bound to the separator well in a hot pressing process, so as to improve an interface bonding effect.