Negative Electrode Porosity Gradient for Uniform Electrolyte Infiltration
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Solution Overview
Problem
Current methods for increasing the energy density of electrochemical devices, such as lithium-ion batteries, through pressure treatment on electrode plates result in non-uniform porosity, leading to uneven lithium ion transport and adverse battery performance.
Innovation Solution
An electrochemical device with a negative electrode having a specific porosity gradient and an electrolyte solution containing additives with low surface tension, ensuring uniform infiltration and reduced polarization during charging.
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 becomes non-uniform leading to uneven lithium ion transport
Solution Approach 1:
The patent applies local quality by creating a controlled porosity gradient within the electrode plate structure. Different regions of the electrode are designed with different porosity characteristics - the surface layer maintains higher porosity for good electrolyte contact, while deeper layers have progressively lower porosity to increase active material density. This localized differentiation resolves the contradiction by allowing high energy density in bulk while maintaining sufficient ion transport pathways at critical interfaces.
Solution Approach 2:
The patent utilizes parameter changes by systematically varying the porosity parameter through controlled pressure treatment at different stages of electrode fabrication. By applying pressure at specific moments during the stacking process, the patent creates a gradient distribution of porosity values from surface to core, transforming the uniform porosity state into a optimized non-uniform state that balances material density and ion transport requirements.
2Speed
If porosity of upper layer is increased to facilitate lithium ion transport, then ion transport is improved, but electrolyte infiltration into lower layer is delayed
Solution Approach 1:
The patent applies preliminary action by pre-establishing an optimized porosity gradient structure before battery operation begins. During the electrode fabrication process, pressure treatment is applied in advance to create the desired porosity distribution, ensuring that both surface and deep layers have appropriate porosity characteristics ready for immediate electrolyte infiltration and ion transport upon battery activation, eliminating the time delay problem.
Solution Approach 2:
The patent incorporates dynamics by creating a porosity gradient that dynamically balances electrolyte infiltration and ion transport throughout the electrode thickness. The gradual transition of porosity values from surface to core allows electrolyte to progressively penetrate deeper layers while maintaining adequate ion transport pathways at each level, achieving a dynamic equilibrium between infiltration speed and transport efficiency.
3Manufacturing precision
If uniform porosity is maintained to ensure even electrolyte distribution, then electrolyte distribution is improved, but energy density decreases
Solution Approach 1:
The patent applies local quality by designing different porosity characteristics for different regions of the electrode. The surface layer maintains higher porosity to ensure excellent electrolyte distribution and contact, while deeper layers progressively reduce porosity to maximize active material packing density. This localized differentiation allows each region to be optimized for its specific function, resolving the contradiction between uniform distribution and high energy density.
Solution Approach 2:
The patent resolves the contradiction by transitioning from a one-dimensional uniform porosity approach to a three-dimensional porosity gradient structure. By varying porosity in the thickness direction while maintaining lateral uniformity, the patent creates a multi-dimensional optimization where electrolyte distribution is ensured at the surface level while active material density is maximized in the bulk volume, effectively adding a depth dimension to the porosity 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
Enhances charging capabilities and maintains lithium ion transport efficiency by ensuring uniform electrolyte distribution across varying porosity regions on the electrode, improving battery performance.
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
When the porosity of an upper layer of the electrode plate is relatively large, the active material tends to form a positive concentration gradient and facilitates transport of lithium ions inside the electrode plate
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 disposed on a surface of the negative current collector. 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. The additive A is at least one selected from a compound of Formula I or a compound of Formula II (the groups in Formula I and Formula II are defined in the specification): 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%.