Battery Electrode Edge Layout to Prevent Lithium Plating
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Solution Overview
Problem
Electrochemical apparatuses, such as lithium-ion batteries, face challenges in achieving high safety performance and energy density due to lithium precipitation and edge bulging issues during the manufacturing and cycling processes, which affect the energy density and safety of the devices.
Innovation Solution
The electrochemical apparatus design includes a positive electrode plate and a negative electrode plate with specific edge alignments and thickness configurations, where the first negative electrode active material layer exceeds the second negative electrode active material layer, allowing lithium ions to be intercalated without precipitation, and reducing the thickness of the negative electrode active material layer to enhance energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the negative electrode plate extends beyond the positive electrode plate to prevent lithium precipitation, then lithium precipitation is avoided, but the thickness of non-capacity-providing negative electrode material increases, reducing energy density
Solution Approach 1:
The negative electrode plate is divided into two distinct layers: a first negative electrode active material layer that extends beyond the positive electrode plate to prevent lithium precipitation, and a second negative electrode active material layer that is aligned with the positive electrode plate to maximize energy density. This segmentation allows each layer to fulfill different functional requirements simultaneously.
Solution Approach 2:
Different regions of the negative electrode plate are assigned different functions through the two-layer structure. The first layer at the edges provides lithium buffer capacity to prevent precipitation, while the second layer in the central region optimizes for capacity and energy density. This local differentiation resolves the contradiction between safety and efficiency.
2Reliability
If the negative electrode plate is made thicker to provide more lithium intercalation sites, then lithium precipitation is prevented, but the device volume increases and energy density decreases
Solution Approach 1:
Instead of increasing thickness uniformly in one dimension, the solution extends the negative electrode material in the planar dimension (length/width) through the first layer. This dimensional shift provides additional intercalation sites without significantly increasing the device's overall thickness or volume, thereby maintaining high energy density while preventing lithium precipitation.
3Quantity of substance
If the positive and negative electrode plates are aligned with edges perfectly matched, then energy density is maximized, but lithium precipitation occurs on the negative electrode plate
Solution Approach 1:
The negative electrode is segmented into two layers with different spatial extents. The second layer aligns with the positive electrode for optimal energy density, while the first layer extends beyond to provide lithium buffer capacity, preventing precipitation without compromising the aligned region's efficiency.
Solution Approach 2:
The asymmetric configuration where the first negative electrode layer extends beyond the positive electrode plate creates an intentional imbalance. This asymmetry provides the necessary excess negative electrode material at the edges to accommodate lithium ions during cycling, preventing precipitation while maintaining symmetric alignment in the central region for high 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
This configuration effectively avoids lithium precipitation, minimizes energy density loss, and alleviates edge bulging, resulting in improved safety and energy performance of the electrochemical apparatus.
Implementation Method 1
lithium ions released from the positive electrode plate can be intercalated in the first negative electrode active material layer, avoiding precipitation of lithium on the negative electrode plate
Data Source
AI summary
An electrochemical apparatus includes a positive electrode plate including a positive electrode active material layer, and a negative electrode plate includes a negative electrode current collector, a first negative electrode active material layer, and a second negative electrode active material layer, and the first negative electrode active material layer is provided between the negative electrode current collector and the second negative electrode active material layer. In a length direction, the first negative electrode active material layer has a first edge and a second edge, the second negative electrode active material layer has a third edge and a fourth edge, and the positive electrode active material layer has a fifth edge and a sixth edge. The first edge exceeds the third edge and the fifth edge in the length direction. A distance between the third edge and the fifth edge in the length direction is less than 2 mm.