Negative Electrode Density Gradient for Fast Lithium Pre-Doping
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Solution Overview
Problem
Lithium ion pre-doping in electrochemical devices is time-consuming due to the uniform density of active material on both faces of the negative-electrode collector, which limits the efficiency of lithium ion doping.
Innovation Solution
The electrochemical device features a negative electrode with a first active-material layer on one face and a second active-material layer on the opposite face, with a lower density, allowing for intermittent formation and easier lithium ion insertion, along with a copper collector and metallic lithium connection for improved doping efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If uniform density active material layers are formed on both faces of the negative electrode collector, then manufacturing simplicity is maintained, but lithium ion doping time is excessive
Solution Approach 1:
The patent applies local quality by creating a second negative-electrode active-material layer with lower density than the first layer. This non-uniform density distribution optimizes lithium ion insertion pathways in the second layer, enabling faster pre-doping without compromising overall electrode performance
Solution Approach 2:
The negative electrode is segmented into two distinct active-material layers with different densities. The first layer maintains standard density for structural integrity, while the second layer uses lower density to facilitate rapid lithium ion doping, thereby reducing pre-doping time
2Productivity
If the second negative-electrode active-material layer has lower density, then lithium ion doping efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent changes the density parameter of the second negative-electrode active-material layer to be lower than the first layer. This parameter modification enhances lithium ion doping efficiency by creating more accessible insertion sites, while the density difference can be controlled within practical manufacturing tolerances
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 significantly shortens the pre-doping time and enhances lithium ion doping efficiency, enabling faster production of lithium ion capacitors while maintaining sufficient capacitance.
Implementation Method 1
wherein the first and second negative-electrode active-material layers are pre-doped with lithium ions as metallic lithium is electrically connected
Implementation Method 2
the second negative-electrode active-material layer whose density of negative-electrode active material is lower than that of the first negative-electrode active-material layer
Data Source
AI summary
An electrochemical device has a positive electrode, a negative electrode, separators, and an electrolyte. The negative electrode has: a negative-electrode collector having a first principal face and a second principal face on the opposite side of the first principal face; a first negative-electrode active-material layer formed on the first principal face; and a second negative-electrode active-material layer which is formed intermittently on the second principal face and whose density of negative-electrode active material is lower than that of the first negative-electrode active-material layer. In the electrolyte, the positive electrode, negative electrode, and separators are immersed. The electrochemical device is such that the first and second negative-electrode active-material layers are pre-doped with lithium ions as a metallic lithium is electrically connected to the second principal face where the second negative-electrode active-material layer is not formed, and then immersed in the electrolyte.