Silane Electrolyte Additive for Silicon Anode Cycle Stability
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Solution Overview
Problem
Lithium-ion secondary batteries using silicon-based negative electrode materials face challenges in maintaining cycle characteristics and preventing battery inflation due to decomposition reactions and swelling, which are not as effective as those using carbon-based active materials.
Innovation Solution
A non-aqueous electrolyte liquid containing a silane compound with alkenyl and arylethynyl groups is used, which forms a stable coating on the silicon-based negative electrode, inhibiting decomposition reactions and battery inflation, and improving cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode material is used to increase battery capacity, then battery capacity increases, but cycle characteristics deteriorate due to decomposition reactions and battery inflation
Solution Approach 1:
A silane compound is introduced as an intermediary substance in the electrolyte liquid that mediates between the silicon-based negative electrode material and the electrolyte. The silane compound preferentially reacts with the silicon surface to form a stable coating layer, preventing direct contact and harmful decomposition reactions between the silicon and electrolyte, thereby improving cycle characteristics while maintaining high capacity
Solution Approach 2:
The chemical composition and structure of the electrolyte liquid are changed by incorporating specific silane compounds with controlled molecular structures (containing Si-O-Si bonds and specific functional groups). This parameter change in the electrolyte composition enables the formation of stable protective films on the silicon surface, transforming the unstable silicon-electrolyte interface into a stable system that maintains both high capacity and good cycle characteristics
2Quantity of substance
If silicon-based negative electrode material is used, then theoretical capacity increases ten times or more compared to graphite, but the negative electrode active material expands and contracts causing cracking
Solution Approach 1:
The silane compound acts as a cushioning layer formed beforehand on the silicon surface. This protective coating is created prior to battery operation and remains intact during charge-discharge cycles, absorbing and distributing the mechanical stress from silicon expansion and contraction, thereby preventing cracking and maintaining structural integrity throughout battery life
Solution Approach 2:
A composite structure is formed where the silane compound coating (containing Si-O-Si bonds) covers the silicon-based negative electrode material. This composite material combines the high capacity advantage of silicon with the protective benefits of the silane coating, creating a hybrid structure that maintains both high theoretical capacity and structural strength during cycling
3Reliability
If fluorine-based electrolyte liquid is used to form stable SEI film on silicon surface, then decomposition reactions are inhibited, but battery cell inflates due to swelling phenomenon
Solution Approach 1:
The electrolyte liquid composition is changed from fluorine-based to silane-based compounds with specific molecular structures containing Si-O-Si bonds. This parameter change in chemical composition enables the formation of protective films that not only inhibit decomposition reactions but also accommodate silicon expansion without causing battery swelling, thus resolving both issues simultaneously
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 use of the silane compound in the non-aqueous electrolyte liquid enhances battery cycle characteristics and prevents battery inflation, achieving performance comparable to carbon-based active material batteries.
Implementation Method 1
a decomposition reaction of the electrolyte liquid occurs on the new surface, and a coating being a decomposed product of the electrolyte liquid is formed on the new surface
Implementation Method 2
repeated charge and discharge consume the fluorine-based solvent to increase a decomposed product of the electrolyte liquid deposited on a surface of the silicon material, and lithium moving reversibly is deactivated with incorporation into the decomposed product to deteriorate the battery cycle characteristics. In addition, a battery cell inflates due to a swelling phenomenon
Data Source
AI summary
A non-aqueous electrolyte liquid including: a non-aqueous solvent; an electrolyte salt dissolved in the non-aqueous solvent; and a silane compound represented by the following general formula (1),Si(R1)l(R2)m(R3)n(R4)4-l-m-n(1)wherein R represents an alkenyl group having 2 to 20 carbon atoms, R2 represents a substituted or unsubstituted arylethynyl group having 8 to 20 carbon atoms, R3 represents an alkyl group having 1 to 20 carbon atoms, R4 represents an alkynyl group having 2 to 20 carbon atoms, “l” and “m” each independently represent an integer of 1 to 3, “n” represents an integer of 0 to 2, and “l”, “m”, and “n” represent integers satisfying 2≤l+m+n≤4.