Negative Electrode Porosity Gradient and Electrolyte Wetting
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Solution Overview
Problem
Current methods for increasing energy density in electrochemical devices, such as lithium-ion batteries, face challenges due to non-uniform pressure treatment leading to porosity gradients in electrode plates, which hinder lithium ion transport and battery performance.
Innovation Solution
An electrochemical device with a negative electrode having distinct sections of identical thickness and porosity ratios, combined with an electrolyte solution containing specific additives that reduce surface tension, ensuring uniform infiltration and enhanced charging capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pressure treatment is applied to increase active material on electrode plate, then energy density is improved, but porosity gradient forms causing non-uniform lithium ion transport
Solution Approach 1:
The electrode plate is divided into multiple sections (first section, second section, third section) with different porosity characteristics. Each section has controlled porosity to optimize lithium ion transport while maintaining high active material loading. This segmentation allows different regions to serve different functions in the electrochemical process.
Solution Approach 2:
Different sections of the electrode plate are given different local porosity properties. The first section has higher porosity to facilitate electrolyte infiltration, while the third section has lower porosity to maintain structural integrity. This local quality variation resolves the contradiction between high active material loading and uniform porosity.
2Speed
If porosity of upper layer is increased to facilitate lithium ion transport, then charging speed is improved, but electrolyte infiltration into lower layer is delayed
Solution Approach 1:
The electrode plate structure is pre-designed with a porosity gradient before operation. The first section has higher porosity prepared in advance to enable rapid electrolyte infiltration, while subsequent sections have progressively lower porosity. This preliminary structuring ensures that electrolyte can quickly penetrate the upper layers without delaying infiltration into lower layers.
Solution Approach 2:
The porosity is varied in the thickness direction (vertical dimension) of the electrode plate, creating a gradient structure. This dimensional variation allows different porosity values at different depths, optimizing both rapid electrolyte infiltration and efficient lithium ion transport simultaneously.
3Productivity
If additive A with low surface tension is introduced, then electrolyte infiltration is accelerated, but device complexity increases
Solution Approach 1:
The surface tension parameter of the electrolyte is modified by adding additive A. This chemical parameter change reduces surface tension, enabling faster and more uniform electrolyte infiltration into the porous electrode structure. The additive acts as a surfactant to improve wetting properties without significantly complicating the overall device design.
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 ensures uniform distribution of the electrolyte solution across different porosity regions, reducing polarization and improving charging efficiency and low-temperature discharge capacity retention.
Implementation Method 1
By introducing an appropriate amount of additive A of a relatively low surface tension into the electrolyte solution, this application can reduce the surface tension of the electrolyte solution, accelerate infiltration of the electrolyte solution
Implementation Method 2
ensure that the electrolyte solution is distributed sufficiently and uniformly in regions of different porosities on the negative electrode mixture layer
Implementation Method 3
thereby reducing polarization during charging of the electrochemical device and enhancing the charging capabilities
Data Source
AI summary
An electrochemical device includes a negative electrode and an electrolyte solution. The negative electrode includes a negative current collector and a negative electrode mixture layer. The negative electrode mixture layer includes a first section, a second section, and a third section arranged sequentially in a thickness direction. The first section, the second section, and the third section are of an identical thickness. A ratio of a porosity P1 of the first section to a porosity P2 of the third section is P. The electrolyte solution includes an additive A, which is at least one selected from a compound of Formula I or a compound of Formula II:Based on a total mass of the electrolyte solution, a mass percent of the additive A is w %, satisfying 1≤w≤60, P=P1/P2, and P/(w %+1)≥50%.