Negative Electrode Edge Layout to Prevent Lithium Plating
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Solution Overview
Problem
Existing electrochemical devices, such as lithium-ion batteries, face challenges in maintaining balanced lithium deintercalation and intercalation, leading to lithium plating and capacity loss due to kinetic performance disparities between different parts of the negative electrode plate, which affects energy density and cycle performance.
Innovation Solution
The electrochemical device features a negative electrode plate with a first and second negative active material layer, where the second layer protrudes beyond the first, and their edges are aligned to optimize lithium ion transmission, ensuring superior kinetic performance and preventing lithium plating, while maintaining high energy density and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the negative electrode plate has a single uniform active material layer, then the manufacturing process is simple, but kinetic performance is insufficient leading to lithium plating
Solution Approach 1:
The negative electrode active material layer is divided into multiple layers with different kinetic performances. The first negative active material layer has superior kinetic performance and is positioned to protrude beyond the positive electrode plate, while the second layer has lower kinetic performance. This segmentation allows different regions to perform different functions, preventing lithium plating at the edges while maintaining overall battery performance.
Solution Approach 2:
Different regions of the negative electrode are assigned different material properties. The first negative active material layer uses materials or structures optimized for fast lithium ion insertion/extraction (superior kinetics), while the second layer uses materials optimized for capacity. This local differentiation of material quality ensures that the edge regions with higher lithium flux have superior kinetic performance.
2Reliability
If the negative electrode protrudes significantly beyond the positive electrode, then lithium plating is prevented, but capacity loss occurs due to unused active material
Solution Approach 1:
The first negative active material layer protrudes beyond the positive electrode plate by a controlled distance (0.5-5mm), which is sufficient to prevent lithium plating at the edges but not excessive to cause significant capacity loss. This partial protrusion optimizes the balance between lithium plating prevention and energy density maintenance.
Solution Approach 2:
The protrusion distance between the negative and positive electrode plates is optimized as a key parameter. By controlling the protrusion distance to be within 0.5-5mm, the system achieves optimal performance in preventing lithium plating while minimizing capacity loss from unused active material.
3Quantity of substance
If the edges of negative and positive electrode plates are perfectly aligned, then energy density is maximized, but lithium plating occurs due to insufficient lithium accommodation space
Solution Approach 1:
The negative electrode plate is designed with asymmetric protrusion relative to the positive electrode plate. The first negative active material layer extends beyond the positive electrode plate edges, creating an asymmetric configuration that provides additional lithium accommodation space at the edges without significantly reducing overall energy density.
4Reliability
If different negative active material layers have different kinetic performances, then lithium ion transmission is optimized, but manufacturing precision requirements increase
Solution Approach 1:
The function of preventing lithium plating is extracted and assigned to the first negative active material layer with superior kinetic performance, which protrudes beyond the positive electrode. This separates the lithium plating prevention function from the capacity storage function, allowing each layer to be optimized independently while simplifying the overall manufacturing alignment requirements.
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
This configuration effectively prevents lithium plating and maintains high cycle performance by aligning the edges of the negative active material layers with the positive active material layer, ensuring efficient lithium ion intercalation and deintercalation, thus enhancing the energy density and minimizing capacity loss.
Implementation Method 1
lithium ions released from the positive electrode plate can be intercalated into the second negative active material layer
Implementation Method 2
ensuring efficient lithium ion intercalation and deintercalation
Data Source
AI summary
An electrochemical device includes a positive electrode plate which includes a positive active material layer and a negative electrode plate which includes a negative current collector, a first negative active material layer, and a second negative active material layer. In a length direction, the first negative active material layer includes a first edge and a second edge opposite to the first edge. In the length direction, the second negative active material layer includes a third edge and a fourth edge opposite to the third edge. In the length direction, the positive active material layer includes a fifth edge and a sixth edge opposite to the fifth edge. The third edge protrudes beyond the first edge and the fifth edge in the length direction. A distance between the first edge and the fifth edge in the length direction of the negative electrode plate is less than 2 mm.