Electrolyte Mixture for Silicon Anode SEI Control
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Solution Overview
Problem
High silicon loading in lithium ion batteries makes the negative electrode sensitive to electrolyte formulation, leading to electrolyte decomposition and the formation of a solid electrolyte interphase (SEI) layer that blocks lithium ion transfer channels, compromising battery performance.
Innovation Solution
An electrolyte mixture of dimethyl carbonate (DMC) and fluoroethylene carbonate (FEC) with a non-polymerizing SEI precursor additive and a solvent additive is used, forming a controlled SEI layer that prevents further reaction between silicon and the electrolyte, maintaining open pores for lithium ion transfer and improving electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high silicon loading is used in the negative electrode, then battery energy density is improved, but electrolyte decomposition occurs and SEI layer blocks lithium ion transfer channels
Solution Approach 1:
The electrolyte formulation includes SEI precursor additives that pre-form a stable solid electrolyte interphase layer on the silicon surface before lithium ion transfer begins. This preliminary SEI formation prevents subsequent electrolyte decomposition and maintains open lithium ion transfer channels during battery cycling
Solution Approach 2:
The patent modifies electrolyte composition parameters by incorporating specific ratios of cyclic carbonate (15-30 vol%) and chain carbonate (70-85 vol%), along with SEI precursor additives (5-20 wt% of total electrolyte weight). These parameter changes optimize both energy density and lithium ion conductivity
2Quantity of substance
If conventional electrolyte formulation is used with high silicon loading, then battery capacity increases, but SEI layer formation blocks pores and compromises performance
Solution Approach 1:
SEI precursor additives act as intermediaries that form a protective interface layer between the silicon negative electrode and the bulk electrolyte. This intermediary SEI layer prevents direct contact between electrolyte and silicon, eliminating harmful electrolyte decomposition while maintaining battery capacity
Solution Approach 2:
The electrolyte is formulated as a composite system combining cyclic carbonate, chain carbonate, and SEI precursor additives in specific proportions. This composite electrolyte composition creates a synergistic effect where each component contributes to forming a stable, conductive SEI layer that enables high capacity without performance degradation
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 results in a stable, electronically insulating SEI layer with suitable thickness, enhancing kinetic stability and maintaining lithium ion conductivity, thereby improving battery cycling performance and energy density.
Implementation Method 1
forming a controlled SEI layer that prevents further reaction between silicon and the electrolyte
Implementation Method 2
maintaining open pores for lithium ion transfer
Implementation Method 3
stable, electronically insulating SEI layer
Data Source
AI summary
An example electrolyte includes a solvent mixture, a lithium salt, a non-polymerizing solid electrolyte interface (SEI) precursor additive, and a solvent additive. The solvent mixture includes dimethyl carbonate (DMC) and fluoroethylene carbonate (FEC) present in a volume to volume ratio ranging from 20 to 1 to 1 to 20. The non-polymerizing SEI precursor additive is present in an amount ranging from greater than 0 wt % to about 10 wt % of a total wt % of the electrolyte, and the solvent additive is present in an amount ranging from greater than 0 wt % to about 10 wt % of the total wt % of the electrolyte.