Lithium Battery Negative Electrode Current Collector Protrusion Design
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Solution Overview
Problem
Lithium secondary batteries face challenges in reducing the expansion of the negative electrode due to lithium metal deposition, leading to degraded discharge capacity and cycle characteristics, as existing solutions like porous current collectors do not sufficiently minimize volume changes.
Innovation Solution
The lithium secondary battery incorporates a negative electrode current collector with protrusions on both surfaces, arranged such that the total area of overlap between the protrusions is ½ or less, creating spaces for lithium metal deposition, which reduces the electrode's expansion and enhances charge/discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a porous metal current collector with lithium metal intercalated in the pores is used, then the capacity of the battery is improved, but the expansion of the negative electrode increases due to lithium metal deposition
Solution Approach 1:
The current collector surface is segmented into protruding portions and recessed portions, creating a three-dimensional structure. The protruding portions serve as deposition sites for lithium metal during charge, while the recessed portions accommodate the deposited lithium during discharge, preventing electrode expansion while maintaining high capacity
Solution Approach 2:
The invention transitions from a flat two-dimensional current collector surface to a three-dimensional structure with protruding and recessed portions. This dimensional change provides additional space for lithium metal deposition and accommodation, resolving the contradiction between capacity enhancement and volume stability
2Reliability
If the surface irregularity of the negative electrode current collector is reduced, then dendritic deposition is limited, but the capacity increase is restricted
Solution Approach 1:
The current collector is designed with localized protruding portions that create specific deposition sites with controlled surface characteristics. These localized structures provide suitable surfaces for uniform lithium metal deposition without causing dendritic growth, while the overall electrode structure maintains high capacity through the three-dimensional configuration
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 effectively minimizes the expansion of the negative electrode, improves discharge capacity, and enhances safety by uniformly distributing lithium metal deposition and pressure, leading to increased conductivity and efficiency.
Implementation Method 1
In a lithium secondary battery, lithium metal is deposited on a negative electrode during charge, while the lithium metal dissolves in a nonaqueous electrolyte during discharge.
Implementation Method 2
a nonaqueous electrolyte having lithium-ion conductivity
Data Source
AI summary
A lithium secondary battery includes a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte having lithium-ion conductivity. A negative electrode current collector includes a layer having a first surface and a second surface opposite to the first surface, first protrusions protruding from the first surface, and second protrusions protruding from the second surface. The first and second surfaces are surfaces on which lithium metal is deposited during charge. When viewed in a direction of a normal to the first surface, a total area of overlap between the first protrusions and the second protrusions is ½ or less of a total area of the first protrusions.