Lithium Metal Alloy Anode for Low-Temperature Capacity Retention
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Solution Overview
Problem
Lithium secondary batteries face reduced capacity retention rates due to deactivation of lithium metal caused by volume changes during charging and discharging, leading to decreased conductivity and resistance increases at low temperatures.
Innovation Solution
A lithium secondary battery design incorporating a negative electrode layer with an alloy of lithium metal and a dissimilar metal, where the lithium element percentage is 40.00 to 99.97 atomic % and optionally includes an oxygen-enriched portion, reducing electrolyte resistance and enhancing affinity with the separator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If lithium metal is used as negative electrode active material, then high output voltage is achieved, but capacity retention rate is reduced due to deactivation caused by volume change during charging and discharging
Solution Approach 1:
The negative electrode layer uses a composite structure containing lithium metal particles dispersed in an alloy matrix consisting of dissimilar metals (e.g., Al-Si-Mg alloy). This composite approach allows the lithium metal to provide high output voltage while the alloy matrix accommodates volume changes and prevents deactivation, thereby maintaining capacity retention rate.
Solution Approach 2:
The alloy matrix acts as an intermediary between the lithium metal particles and the electrolyte/separator. It provides a stable structural framework that mediates the volume expansion and contraction of lithium metal during charging and discharging, preventing direct contact issues and maintaining electrical conductivity throughout cycles.
2Duration of action of moving object
If lithium metal undergoes volume change during charging and discharging, then deposition and dissolution reactions occur, but conductivity decreases and resistance increases at low temperatures
Solution Approach 1:
The invention changes the physical and chemical parameters of the negative electrode by using an alloy matrix with specific compositional ranges (e.g., Al: 60-90 atomic %, Si: 5-30 atomic %, Mg: 1-20 atomic%). These parameter changes create an alloy with optimized mechanical properties and electrical conductivity that remains stable across temperature variations, preventing resistance increase at low temperatures.
Solution Approach 2:
The negative electrode layer exhibits local quality differentiation where lithium metal particles are distributed within the alloy matrix. The alloy regions provide structural stability and conductivity, while lithium-rich regions provide active reaction sites. This local differentiation ensures that conductivity is maintained in the alloy framework even when lithium volume changes occur.
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
Improves capacity retention rates and maintains high low-temperature output by minimizing electrolyte resistance and reducing cracks in the negative electrode layer, thereby stabilizing the battery performance.
Implementation Method 1
a negative electrode in which deposition and dissolution reactions of lithium metal occur
Implementation Method 2
reducing electrolyte resistance and enhancing affinity with the separator
Data Source
AI summary
A lithium secondary battery includes a positive electrode, and a negative electrode in which deposition and dissolution reactions of lithium metal occur. The negative electrode includes a negative electrode layer. The negative electrode layer contains, as a negative electrode active material, an alloy of the lithium metal and dissimilar metal. An element percentage of lithium element in the alloy is 40.00 atomic % or more and 99.97 atomic % or less when the lithium secondary battery is fully charged.