Silicon Anode Active Material Purification for Uniform Li-Ion Diffusion
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Solution Overview
Problem
Silicon-based negative electrodes in lithium secondary batteries face issues such as rapid volume expansion, non-uniform reactions, and metal impurities leading to cell short-circuits and reduced life performance due to metal ion precipitation and dendrite formation.
Innovation Solution
A negative electrode active material with a controlled proportion of Si-Fe or Si-Fe-Ti phases and metal impurities, manufactured through a process involving pulverization and acid-cleaning with a mixture of two or more types of acids, effectively removes metal impurities and ensures uniform lithium ion diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based compound is used as negative electrode active material to increase capacity, then discharge capacity is improved, but volume expansion occurs during charging which disconnects conductive path and degrades battery characteristics
Solution Approach 1:
A carbon coating layer is formed on the surface of the silicon-based active material particles. This thin film shell accommodates the volume expansion of silicon during charging while maintaining structural integrity and preserving the conductive path, thus resolving the contradiction between high capacity and conductive path stability.
2Quantity of substance
If silicon-based compound is used as negative electrode active material, then capacity is increased, but non-uniform reactions occur between upper and lower ends of electrode resulting in delamination
Solution Approach 1:
The carbon coating is applied locally on the surface of each silicon-based active material particle, creating a uniform protective layer that ensures consistent reaction behavior across all particles in the electrode, including those at upper and lower ends, thereby achieving uniform reactions and preventing delamination.
3Ease of manufacture
If metal impurities are present in negative electrode active material, then manufacturing is simplified, but metal ions precipitate causing cell short-circuits and reduced life performance
Solution Approach 1:
Metal impurities are extracted and removed from the silicon-based active material through acid treatment before carbon coating. This extraction process eliminates the source of metal ion precipitation that causes short-circuits and performance degradation, while the subsequent carbon coating provides an additional protective barrier.
4Productivity
If FeSi2 with metal impurities is present in electrode, then lithium ion diffusion is hindered leading to concentrated reactions in upper layer portion, but removing metal impurities requires additional processing steps
Solution Approach 1:
The acid treatment to remove metal impurities and the carbon coating formation are combined into a sequential process where acid treatment first eliminates FeSi2 and other metal impurities that hinder lithium ion diffusion, followed by carbon coating that further protects the silicon particles. This combined approach improves lithium ion diffusion efficiency while managing manufacturing complexity.
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 prevents cell short-circuits, enhances life performance, and maintains high energy density by ensuring uniform lithium ion diffusion and stable capacity, thereby improving the overall battery performance.
Implementation Method 1
acid-cleaning with a mixture of two or more types of acids
Implementation Method 2
uniform lithium ion diffusion
Data Source
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AI summary
The present application relates to a negative electrode active material, a method for manufacturing a negative electrode active material, a negative electrode composition, a negative electrode for a lithium secondary battery including the same, and a lithium secondary battery including a negative electrode.