Positive Electrode Inert Layer Layout for Overhang Lithium Plating
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Solution Overview
Problem
Lithium plating in the overhang-specific region of lithium-ion batteries is a significant challenge due to kinetic weak spots, leading to potential battery failure, especially during high-rate charging and low temperature conditions, where existing solutions either compromise energy density or fail to fully address the issue.
Innovation Solution
A secondary battery design with a positive electrode plate and a negative electrode plate, where an inert layer with controlled thickness and silicon content is applied to the positive active material layer, reducing lithium ion deintercalation speed and alleviating plating issues while maintaining high energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the charging speed is increased to meet fast-charge requirements, then the power and charging rate improve, but lithium plating occurs in the overhang-specific region causing reliability degradation
Solution Approach 1:
The patent applies different treatments to different regions of the positive electrode plate. An inert layer is specifically formed on the edges and corners (overhang-specific regions) where lithium plating is most prone to occur, while the central region maintains its original structure. This localized modification allows high-rate charging in the center while preventing plating at the edges.
Solution Approach 2:
The inert layer is formed in advance on the positive electrode plate before battery assembly and operation. This preliminary protective layer is deposited on the edges and corners to prevent lithium plating before it can occur during fast charging operations, rather than attempting to address plating after it forms.
2Quantity of substance
If the positive active material layer thickness is increased to improve energy density, then the energy density improves, but the lithium ion deintercalation kinetics worsen leading to increased plating risk
Solution Approach 1:
The inert layer is selectively applied to the edges and corners of the positive electrode plate where the path length for lithium ion deintercalation is longest. This localized approach addresses the kinetic bottleneck at critical regions without requiring thinning of the entire positive active material layer, thereby preserving overall energy density while improving local deintercalation kinetics.
3Reliability
If an inert layer is added to the positive electrode plate to prevent lithium plating, then the reliability improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The inert layer acts as an intermediary substance between the positive active material and the electrolyte/Li metal. This intermediate layer specifically at the edges and corners mediates the interaction to prevent direct contact that causes plating, while maintaining ionic conductivity for normal operation. The inert layer serves as a protective mediator without requiring fundamental redesign of the electrode architecture.
4Reliability
If the inert layer width is increased to better cover the overhang-specific region, then the lithium plating prevention improves, but the energy density decreases due to reduced active material area
Solution Approach 1:
The inert layer is applied only to the edges and corners (overhang-specific regions) of the positive electrode plate, not to the entire surface. This localized coverage prevents lithium plating at the critical edge regions where the negative electrode overhangs, while leaving the majority of the positive active material area exposed and available for electrochemical reactions, thereby preserving energy density.
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 effectively reduces lithium plating in the overhang-specific region, ensuring stable battery performance even under extreme conditions without compromising energy density, by controlling the thickness of the positive active material layer, silicon mass percent, and inert layer width.
Implementation Method 1
reduces the speed of deintercalating lithium ions from a region covered by the inert layer
Data Source
Figure 1~3
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Figure 6~7
AI summary
A positive electrode plate (10) includes a positive current collector (13) and a positive active material layer (12). A thickness of the positive active material layer (12) is D µm, 30 ≤ D ≤ 200. A negative electrode plate (20) includes a negative current collector (23) and a negative active material layer (22). The positive active material layer (12) is oriented toward the negative active material layer (22). In a width direction (Y) of the positive electrode plate (10), the negative active material layer (22) includes two opposite first edges (24), and the positive active material layer (12) includes two opposite second edges (14). The two second edges (14) are located between the two first edges (24). An inert layer (11) is provided on a surface of the positive active material layer (12). The inert layer (11) coincides with at least a part of the second edges (14). A mass percent of silicon in a region of 15 µm × 15 µm on the inert layer (11) is B%, 0.1 ≤ B ≤ 6.0, and 0.15 ≤ BD/100 ≤ 12.00.