Cyanate Electrolyte for Silicon Anodes and High-Voltage Stability
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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 of conventional electrolytes, and inferior cycle life due to volumetric expansion and electrolyte decomposition, leading to reduced energy and power density and safety concerns.
Innovation Solution
An electrolyte system comprising a cyanate-based compound, a linear carbonate, and a Li-containing salt is introduced, which stabilizes the solid electrolyte interphase layer, reduces electrolyte reactions, and enhances thermal stability, thereby improving the electrochemical performance and safety of silicon-based anode batteries.
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 electrolyte contains cyanate-based compounds that preemptively form a stable protective layer on the silicon anode surface before degradation occurs. This preliminary protective action prevents the harmful volumetric expansion effects during subsequent cycling, allowing the silicon to maintain structural integrity while delivering high capacity.
Solution Approach 2:
The cyanate-based electrolyte additive acts as an intermediary between the silicon anode and the bulk electrolyte. It forms a stable interfacial layer that mediates the interaction, preventing direct contact between the expanding silicon and the unstable bulk electrolyte, thereby maintaining cycling stability while enabling high capacity operation.
2Power
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 invention modifies the chemical composition parameters of the electrolyte by incorporating cyanate-based compounds with specific molecular structures. This parameter change increases the oxidation potential of the electrolyte system, allowing it to remain stable at voltages beyond 4.5 V while maintaining ionic conductivity through the linear carbonate components.
Solution Approach 2:
The electrolyte is formulated as a composite system combining linear carbonates (for ionic conductivity), cyclic carbonates (for solvation), and cyanate-based additives (for oxidative stability). This composite approach synergistically achieves high power delivery through ionic conduction while preventing oxidative decomposition at elevated voltages.
3Quantity of substance
If high-voltage cathodes such as Ni-rich NCM or NCA are paired with silicon anodes, then energy density is improved, but interfacial instability and electrolyte decomposition occur
Solution Approach 1:
The cyanate-based electrolyte additive serves as an intermediary at both electrode interfaces. At the high-voltage cathode interface, it forms a stable protective layer that prevents electrolyte decomposition and transition metal dissolution. At the silicon anode interface, it stabilizes the SEI layer. This dual intermediary action enables the high-energy-density combination of silicon anodes and Ni-rich cathodes to operate stably.
Solution Approach 2:
The electrolyte formulation provides different local functions at different interfaces: the cyanate-based compounds preferentially adsorb and form stable layers at high-voltage cathode surfaces to prevent oxidation and metal dissolution, while simultaneously stabilizing the silicon anode interface. This local quality differentiation addresses the specific stability requirements of each electrode type.
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 system improves the cycle life and rate capability of silicon-based anode batteries by forming stable interface layers, reducing capacity fade, and enhancing thermal stability, thus addressing the limitations of existing electrolytes.
Implementation Method 1
an unstable solid electrolyte interphase (SEI) layer can develop on the surface of the cycled anodes. As the active material expands and contracts during each charge-discharge cycle, unreacted Si surfaces in the active material can subsequently be exposed to the liquid electrolyte and form thicker SEI layers.
Implementation Method 2
The proposed electrolyte system improves the cycle life and rate capability of silicon-based anode batteries by forming stable interface layers
Implementation Method 3
reduces electrolyte reactions, and enhances thermal stability, thereby improving the electrochemical performance and safety of silicon-based anode batteries
Implementation Method 4
oxidative instability of the conventional non-aqueous electrolyte takes place at voltages beyond 4.5 V, which can lead to accelerated decay of cycling performance
Data Source
AI summary
Electrolytes and electrolyte additives for energy storage devices comprising cyanate based compounds 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 comprising at least two electrolyte co-solvents, wherein at least one electrolyte co-solvent comprises a cyanate based compound.