Propionate Electrolyte Composition for Silicon-Carbon Anode SEI Stability
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Solution Overview
Problem
Secondary batteries using a silicon-carbon material as a negative electrode active material face issues with non-uniform surface structure due to disruption of the solid electrolyte interface (SEI) film at high temperature, leading to increased gas generation and reduced discharge capacity under high-rate conditions.
Innovation Solution
The electrolyte solution is formulated with a specific mass ratio of ethyl propionate to propyl propionate (1.7 to 5.7) along with additives like vinylene carbonate, boron-containing lithium salts, or compounds represented by Formula I, promoting a uniform SEI film formation and enhancing high-rate discharge performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a carbonate ester compound is used as the electrolyte solution, then the secondary battery can operate under normal conditions, but the electrolyte solution becomes unstable under high-rate conditions and deteriorates battery performance
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte solution by replacing carbonate ester compounds with propionate esters (ethyl propionate and propyl propionate) in specific ratios. This parameter change transforms the electrolyte's properties to achieve both stability and high-rate performance, resolving the contradiction between reliability and productivity.
Solution Approach 2:
The patent uses a composite electrolyte system combining multiple propionate ester components (ethyl propionate and propyl propionate) with specific mass ratios, along with additives like vinylene carbonate and boron-containing lithium salts. This composite approach creates synergistic effects that simultaneously improve stability and high-rate discharge performance.
2Adaptability or versatility
If the mass ratio of ethyl propionate to propyl propionate is not controlled within 1.7≤a/b≤5.7, then the electrolyte composition can be varied freely, but the surface wettability of silicon-carbon material and SEI film uniformity deteriorate
Solution Approach 1:
The patent establishes a specific parameter range (1.7≤a/b≤5.7) for the mass ratio of ethyl propionate to propyl propionate. This parameter control ensures optimal surface wettability and SEI film uniformity on silicon-carbon material, resolving the contradiction between composition flexibility and manufacturing precision.
3Power
If the secondary battery is discharged at a high rate, then the power output increases, but the internal impedance increases and gas production increases
Solution Approach 1:
The patent changes the electrolyte composition parameters to use propionate esters with specific ratios and additives, which modifies the electrochemical reactions during high-rate discharge. This reduces gas production while maintaining high power output, resolving the contradiction between power and harmful factors.
Solution Approach 2:
The patent converts the potential harm of high-rate discharge (gas production and impedance increase) into beneficial outcomes by using the specific electrolyte composition to promote uniform SEI film formation, which actually reduces gas production and stabilizes impedance during high-power discharge.
4Temperature
If the SEI film on silicon-carbon material is disrupted at high temperature, then the battery can operate at elevated temperatures, but the surface structure becomes non-uniform and gas generation increases
Solution Approach 1:
The patent changes the electrolyte composition to propionate esters with specific ratios and additives, which modifies the SEI film formation characteristics. This enables the battery to operate at high temperatures while maintaining uniform surface structure and reducing gas generation, resolving the contradiction between temperature and harmful factors.
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 significantly reduces gas generation and improves cycle characteristics and high-rate discharge performance by ensuring uniform electrode reactions and lithium intercalation/deintercalation, thereby enhancing the battery's kinetic performance.
Implementation Method 1
a uniform SEI film can be formed on the surface of the silicon-carbon material
Implementation Method 2
inducing uniform intercalation and deintercalation of lithium on the negative electrode
Implementation Method 3
the electrode reaction on the negative electrode can be promoted to occur uniformly
Data Source
AI summary
A secondary battery includes a positive electrode, a negative electrode, a separator, and an electrolyte solution. A negative electrode active material of the negative electrode includes a silicon-carbon material. The electrolyte solution includes ethyl propionate and propyl propionate. Based on a total mass of the electrolyte solution, a mass percentage of the ethyl propionate is a %, and a mass percentage of the propyl propionate is b %, and 1.7≤a/b≤5.7. The electrolyte solution further includes at least one of vinylene carbonate, a boron-containing lithium salt, or a compound containing a structural formula represented by Formula I:where, A in Formula I is selected from C2 to C5 alkylenes.