Lithium Metal Negative Electrode Composite Layer Design
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Solution Overview
Problem
Lithium secondary batteries using lithium metal as a negative electrode face reduced capacity retention due to volume changes during charging and discharging, leading to deactivation of lithium metal and decreased performance.
Innovation Solution
A negative electrode configuration featuring a composite layer of lithium metal alloyed with a dissimilar metal, such as magnesium or bismuth, and a single lithium metal layer, where the dissimilar metal forms a solid solution or intermetallic compound with lithium, is used. This configuration is deposited on a current collector, with specific thickness ratios and lithium content to minimize cracking and electrolyte interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a lithium metal layer is used as a negative electrode active material, then high output voltage is achieved, but capacity retention rate is reduced due to volume change during charging and discharging
Solution Approach 1:
The negative electrode layer is segmented into multiple functional layers: a composite layer containing lithium metal and dissimilar metal particles, and a porous coating layer. This segmentation allows the lithium metal to be distributed within a matrix structure that accommodates volume changes, preventing deactivation while maintaining high output voltage
Solution Approach 2:
A composite layer is formed by combining lithium metal with dissimilar metal particles (such as magnesium, bismuth, palladium, tin, silicon, gold, silver, platinum, zinc, aluminum, indium, strontium, barium, gallium, calcium, or germanium). This composite structure allows the dissimilar metal to form solid solutions or intermetallic compounds with lithium, accommodating volume expansion and contraction during charging-discharging cycles, thereby improving capacity retention while maintaining high output voltage
2Quantity of substance
If the thickness of the single lithium metal layer is increased, then capacity is increased, but cracking and deactivation occur more frequently
Solution Approach 1:
Different regions of the negative electrode are given different properties: the composite layer contains lithium metal distributed within a dissimilar metal matrix that provides structural support, while the porous coating layer provides additional protection. This local quality differentiation allows sufficient lithium quantity while preventing cracking through the distributed composite structure
Solution Approach 2:
The dissimilar metal particles are pre-distributed within the composite layer before lithium metal deposition, creating a pre-formed matrix structure that can accommodate subsequent lithium volume changes. This preliminary action prevents cracking by establishing a supportive framework before the lithium metal is fully in place
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 enhances capacity retention and low-temperature output characteristics by reducing reaction resistance and cracking, thereby improving the overall performance and longevity of lithium secondary batteries.
Implementation Method 1
The dissimilar metal is an element that is able to form a solid solution with the lithium metal or an element that is able to form an intermetallic compound with the lithium metal
Implementation Method 2
The dissimilar metal is an element that is able to form a solid solution with the lithium metal or an element that is able to form an intermetallic compound with the lithium metal
Implementation Method 3
forming a composite layer including an alloy of lithium metal and dissimilar metal by vacuum-depositing the lithium metal and the dissimilar metal on the negative electrode current collector
Data Source
AI summary
A negative electrode for a lithium secondary battery includes a negative electrode current collector and a negative electrode layer. The negative electrode layer includes a composite layer and a single lithium metal layer. The composite layer includes, as a negative electrode active material, an alloy of lithium metal and dissimilar metal. The composite layer and the single lithium metal layer are arranged in this order from the negative electrode current collector. The dissimilar metal is an element that is able to form a solid solution with the lithium metal or an element that is able to form an intermetallic compound with the lithium metal.