Negative Electrode Coating Layout for Better Electrolyte Infiltration
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Solution Overview
Problem
Secondary battery negative electrode plates with high compacted density suffer from poor electrolyte infiltration, leading to lithium metal precipitation and impaired safety and cycling performance due to large ion diffusion impedance.
Innovation Solution
A negative electrode plate design featuring a negative electrode film layer with a middle coating region and edge coating regions of varying thicknesses, where the thickness rebound rate of the edge coating region is greater than that of the middle coating region, ensuring adequate electrolyte absorption and retention, thereby preventing lithium precipitation and enhancing diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If negative electrode plate is designed with large compacted density and high loading capacity, then energy density is improved, but overall porosity decreases leading to poor electrolyte infiltration
Solution Approach 1:
The patent applies local quality by creating different thickness regions within the negative electrode film layer. The edge coating region has a first thickness while the middle coating region has a second thickness that is 5-50 μm smaller. This thickness differentiation creates local porosity variations that facilitate electrolyte infiltration in the middle region while maintaining high compacted density and energy density in the edge regions.
2Use of energy by moving object
If negative electrode plate has high compacted density, then energy density is improved, but ion diffusion impedance increases causing lithium metal precipitation
Solution Approach 1:
The patent creates local quality differentiation by establishing a thickness gradient across the negative electrode film layer. The middle coating region has reduced thickness (5-50 μm smaller than edge region), creating a local pathway with lower ion diffusion impedance. This prevents lithium metal precipitation in the middle region by facilitating adequate electrolyte access and ion transport, while the edge regions maintain high compacted density for energy density.
3Ease of manufacture
If uniform thickness coating is applied, then manufacturing simplicity is maintained, but electrolyte infiltration in middle region is insufficient
Solution Approach 1:
The patent implements local quality by defining specific thickness characteristics for different regions. The edge coating region has a first thickness and the middle coating region has a second thickness that is 5-50 μm smaller. This can be achieved through controlled coating processes that naturally create thickness gradients or through selective removal, providing a balance between manufacturing feasibility and improved electrolyte infiltration in the middle region.
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 design improves the safety and cycling performance of secondary batteries by maintaining uniform thickness during coating, reducing processing costs, and alleviating lithium precipitation and diffusion issues, while maintaining energy density.
Implementation Method 1
thickness of the middle coating region in the fully-charged state is smaller than thickness of the edge coating region in the fully-charged state, so that in the fully-charged state, electrolyte in the central region of the negative electrode plate is not completely extruded
Implementation Method 2
The process of electrolyte infiltration into the electrode plate follows the basic principles of diffusion, diffusing from the edge of the negative electrode plate toward the middle
Data Source
AI summary
A negative electrode plate includes a negative electrode current collector and a negative electrode film layer located on at least one surface of the negative electrode current collector. The negative electrode film layer includes a middle coating region and edge coating regions located on two opposite sides of the middle coating region. Thickness A1 of the edge coating region in a fully-discharged state, thickness B1 of the edge coating region in a fully-charged state, thickness A2 of the middle coating region in the fully-discharged state, and thickness B2 of the middle coating region in the fully-charged state satisfy (B1−A1)/A1>(B2−A2)/A2.