Anode Pre-Dispersion for Silicon Expansion and Conductive Path Stability
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Solution Overview
Problem
Lithium secondary batteries using silicon-containing compounds as negative electrode active materials face challenges due to volume expansion during charging and discharging, which can disconnect the conductive path and deteriorate battery performance, limiting their commercialization and capacity performance.
Innovation Solution
A negative electrode pre-dispersion with a planar conductive material having a BET specific surface area of 100.0 m2/g or more is used, combined with a silicon-containing active material and a dotted conductive material, to improve the dispersibility and maintain the conductive path, thereby enhancing the battery's service life and output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-containing 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 deteriorates battery characteristics
Solution Approach 1:
The patent applies preliminary action by pre-dispersing the conductive material into fine particles (average particle diameter of 1 μm or less) before electrode assembly. This pre-dispersion ensures that conductive material is already positioned in a dispersed state to effectively fill gaps created by silicon volume expansion during charging, maintaining conductive path continuity throughout charge-discharge cycles.
Solution Approach 2:
The patent applies local quality by using conductive material with specific local characteristics - fine particles with average diameter of 1 μm or less are used to specifically target and fill the micro-gaps created by silicon expansion. This localized approach ensures conductive material is precisely where needed to maintain electron transport paths without requiring uniform distribution throughout the entire electrode.
2Stability of the object's composition
If measures are taken to suppress volume expansion such as coating active material layer with thin film or adjusting particle diameter, then volume expansion is reduced, but battery performance deteriorates
Solution Approach 1:
The patent applies the taking out principle by separating the volume stabilization function from the active material itself. Instead of modifying the silicon particles with coatings or composites that might reduce capacity, the patent extracts the volume stabilization function to be performed by the conductive material matrix, which adapts to silicon expansion through its fine particle dispersion and flexibility.
3Quantity of substance
If high capacity silicon-containing compound is used, then energy density is improved, but conductive path disconnection occurs during charging process
Solution Approach 1:
The patent applies parameter changes by fundamentally altering the particle size parameter of the conductive material to an average diameter of 1 μm or less. This parameter change enables the conductive material to effectively fill micro-gaps created by silicon expansion, maintaining conductive path continuity while allowing the use of high-capacity silicon-containing compounds for high energy density.
Data Source
AI summary
A negative electrode pre-dispersion, a negative electrode composition including the same, a negative electrode for a lithium secondary battery including the negative electrode composition, a lithium secondary battery including the negative electrode, and a method for preparing a negative electrode composition are disclosed. The negative electrode pre-dispersion includes a pre-dispersing material comprising a planar conductive material having a BET specific surface area ranging from 100.0 m2/g or more and a water-containing dispersing agent; and a dispersion medium, wherein a solid content of the pre-dispersing material is 10% to 30% based on the negative electrode pre-dispersion.