Silicon Battery Electrolyte Additives for Stable SEI and CEI Films
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Solution Overview
Problem
Lithium-ion batteries with silicon-based anodes and high-voltage nickel-rich cathodes face challenges in long-term cycling stability due to volumetric expansion, unstable solid electrolyte interphase (SEI) layers, and oxidative instability of conventional electrolytes, leading to reduced cycle life and capacity retention.
Innovation Solution
The use of electrolyte additives such as carboxylic ethers, carboxylic acid-based salts, and acrylates to form stable, electronically insulating but ionically conducting SEI layers on silicon anodes and protective cathode electrolyte interphase (CEI) films, enhancing mechanical strength, thermal stability, and reducing flammability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based anodes are used to increase energy density, then capacity is improved, but volumetric expansion during lithiation leads to disintegration and reduced cycling stability
Solution Approach 1:
The patent employs flexible polymer electrolytes that can accommodate the volumetric expansion and contraction of silicon anodes during lithiation and delithiation cycles. The polymer matrix provides mechanical flexibility and elasticity, allowing it to deform with the silicon particles without causing structural disintegration, thereby maintaining electrode integrity over multiple cycles.
Solution Approach 2:
The invention uses composite polymer electrolyte systems combining multiple polymer components (e.g., polyethylene oxide, polypropylene carbonate) with lithium salts. This composite structure provides both mechanical flexibility to handle silicon expansion and sufficient ionic conductivity for battery operation, resolving the contradiction between accommodating volume change and maintaining electrochemical performance.
2Productivity
If conventional non-aqueous electrolytes are used, then ionic conductivity is achieved, but oxidative instability occurs at voltages beyond 4.5 V leading to accelerated decay
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by using polymer electrolytes with different molecular structures, crosslinking densities, and lithium salt concentrations. These parameter adjustments enable the electrolyte to maintain stability at higher voltages beyond 4.5 V while preserving adequate ionic conductivity for battery operation.
Solution Approach 2:
The polymer electrolyte acts as an intermediary between the high-voltage cathode and the silicon anode, providing a chemically stable interface that prevents direct harmful interactions. The polymer matrix mediates the electrochemical reactions, offering both ionic transport pathways and oxidative stability at elevated potentials.
3Quantity of substance
If silicon anodes with high capacity are used, then energy density is improved, but unstable SEI layer formation leads to irreversible capacity loss
Solution Approach 1:
The polymer electrolyte enables the silicon anode to self-stabilize by forming a consistent, protective solid electrolyte interphase (SEI) layer during initial cycles. This self-forming SEI layer prevents further electrolyte decomposition and protects the silicon surface, reducing irreversible capacity loss in subsequent cycles while maintaining high capacity.
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
Improves the electrochemical stability and safety of silicon anode-based lithium-ion batteries by stabilizing the SEI and CEI layers, reducing capacity fade, and enhancing thermal stability, thereby increasing cycle life and energy density.
Implementation Method 1
The use of electrolyte additives such as carboxylic ethers, carboxylic acid-based salts, and acrylates to form stable, electronically insulating but ionically conducting SEI layers on silicon anodes
Implementation Method 2
forming a uniform, stable SEI layer on the surface of Si anodes... the ideal additives should be oxidized preferentially to the solvent molecule in the bare electrolyte, resulting in a protective cathode electrolyte interphase (CEI) film formed on the surface of the NCM (or NCA)
Data Source
AI summary
Electrolytes and electrolyte additives for energy storage devices comprising a carboxylic ether, a carboxylic acid based salt, or an acrylate electrolyte are disclosed. The energy storage device comprises a first electrode and a second electrode, wherein at least one of the first electrode and the second electrode is a Si-based electrode, a separator between the first electrode and the second electrode, an electrolyte, and at least one electrolyte additive selected from carboxylic ethers, carboxylic acid based salts, and acrylates.