Silicon-Based Battery Electrolyte Additives for Stable SEI
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Solution Overview
Problem
Lithium-ion batteries with silicon-based anodes and high-voltage cathodes face challenges such as unstable solid electrolyte interphase layers, oxidative instability, and poor cycling life due to volumetric expansion and transition metal ion dissolution, limiting their energy density and safety.
Innovation Solution
The development of new electrolyte additives that form stable, electronically insulating but ionically conducting solid electrolyte interphase layers on silicon anodes and cathodes, enhancing mechanical strength and thermal stability, and reducing flammability to improve the electrochemical performance and safety of silicon-based lithium-ion batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based anodes are used to increase energy density, then volumetric capacity is improved, but volumetric expansion during lithiation leads to disintegration and reduced cycling life
Solution Approach 1:
The patent employs a flexible polymer electrolyte 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 polymer electrolyte acts as an intermediary between the silicon anode and the rest of the battery system. It forms a stable solid electrolyte interphase (SEI) layer on the silicon surface that mediates the interaction, preventing direct contact between silicon and conventional liquid electrolytes, thus avoiding harmful reactions while still allowing lithium ion transport.
2Reliability
If conventional liquid 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 fundamental parameter of electrolyte state from liquid to solid polymer form. This phase change enables the electrolyte to maintain stability at higher voltages beyond 4.5 V, as the solid polymer structure prevents oxidative decomposition that occurs in liquid electrolytes at these potentials, while still maintaining adequate ionic conductivity for battery operation.
Solution Approach 2:
The polymer electrolyte is formulated as a composite material containing lithium salts dispersed within the polymer matrix. This composite structure combines the mechanical stability and high-voltage resistance of the polymer with the ionic conductivity provided by the lithium salt, achieving both electrochemical stability and functional performance.
3Quantity of substance
If silicon anodes with high capacity are used, then energy density is improved, but unstable SEI layer formation leads to endless electrolyte exposure and irreversible capacity loss
Solution Approach 1:
The polymer electrolyte enables continuous and stable lithium ion transport to and from the silicon anode surface throughout cycling. By maintaining a stable SEI interface, it ensures uninterrupted useful action of lithium insertion and extraction without the breakdown and reforming cycles that cause capacity loss in conventional systems.
Solution Approach 2:
The patent converts the potentially harmful effect of silicon's high reactivity and surface exposure into a benefit by using the polymer electrolyte to form a stable, protective SEI layer. This layer prevents further harmful reactions between silicon and electrolyte while allowing beneficial lithium ion insertion, thus protecting the high-capacity silicon anode.
4Quantity of substance
If high-voltage cathodes such as NCM or NCA are used, then energy density is improved, but transition metal ion dissolution into electrolyte reduces stability
Solution Approach 1:
The solid polymer electrolyte acts as an intermediary barrier between the high-voltage cathode and the battery environment. It forms a stable cathode electrolyte interphase (CEI) on the cathode surface that mediates ion transport while preventing transition metal ion dissolution into the electrolyte, thus maintaining cathode structural stability and composition.
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 proposed electrolyte additives stabilize the solid electrolyte interface, prevent electrolyte reactions, and enhance thermal stability, leading to improved energy density, cycle life, and safety of silicon-based lithium-ion batteries.
Implementation Method 1
form stable, electronically insulating but ionically conducting solid electrolyte interphase layers on silicon anodes
Implementation Method 2
forming a protective cathode electrolyte interphase (CEI) film formed on the surface of the Ni-rich NCM (or NCA) and LCO cathodes
Implementation Method 3
electronically insulating but ionically conducting solid electrolyte interphase layers
Data Source
AI summary
Electrolytes and electrolyte additives for energy storage devices comprising a silicon compound 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 a silicon compound.