Cyanate-Based Battery Electrolytes for Stable Silicon Anodes
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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, leading to reduced energy density and safety concerns due to issues like gas generation and volume swelling in high FEC-containing electrolytes.
Innovation Solution
An electrolyte system comprising a cyanate-based compound, a linear carbonate, and a Li-containing salt, which stabilizes the solid electrolyte interphase, reduces volume expansion, 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 pre-form a stable protective interface layer on the silicon anode surface before degradation can occur. This preliminary protective action prevents subsequent disintegration during lithiation cycles, allowing high capacity silicon anodes to maintain structural integrity and cycling stability.
Solution Approach 2:
The cyanate-based compound acts as an intermediary between the silicon anode and the conventional electrolyte. It forms a stable interfacial layer that mediates the interaction, preventing direct harmful reactions between silicon and electrolyte while enabling stable lithium ion transport, thus resolving the contradiction between high capacity and cycling stability.
2Quantity of substance
If high-voltage cathodes are used to increase energy density, then capacity is improved, but oxidative instability of conventional electrolytes occurs beyond 4.5 V
Solution Approach 1:
The cyanate-based compound serves as an intermediary protective layer on the cathode surface, enabling the use of high-voltage cathodes (beyond 4.5V) by preventing direct oxidative degradation of the conventional electrolyte, thus allowing high capacity operation without electrolyte instability.
Solution Approach 2:
The invention changes the chemical composition parameter of the electrolyte interface by introducing cyanate-based compounds with higher oxidative stability, enabling the system to operate at higher voltages beyond the conventional 4.5V limit while maintaining electrolyte stability and achieving higher capacity.
3Stability of the object's composition
If high FEC-containing electrolytes are used to stabilize the SEI layer, then interfacial stability is improved, but gas generation and volume swelling occur
Solution Approach 1:
The invention changes the chemical composition parameter by substituting part of the FEC with cyanate-based compounds. This parameter change maintains SEI layer stability while reducing the harmful side reactions that cause gas generation and volume swelling, achieving a balanced electrolyte formulation.
Solution Approach 2:
The invention extracts or reduces the excessive FEC content that causes gas generation while retaining enough to maintain SEI stability, and replaces it with cyanate-based compounds that provide stability without the harmful gas-generating side reactions.
4Ease of manufacture
If conventional electrolytes are used with silicon anodes, then manufacturing simplicity is maintained, but cycle life is reduced due to unstable SEI layers
Solution Approach 1:
The invention makes a targeted parameter change by adding small amounts of cyanate-based compounds to conventional electrolyte formulations. This minimal modification maintains manufacturing simplicity while dramatically improving cycle life through stable SEI layer formation, avoiding the need for complete electrolyte system redesign.
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 thermal stability of silicon-based anode batteries, reducing capacity fade and gas generation, while maintaining high energy density and safety by forming stable interfacial layers and minimizing electrolyte decomposition.
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 large volumetric expansion (>300%) during the Li alloying/de-alloying processes can lead to disintegration of the active material and the loss of electrical conduction paths
Implementation Method 3
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
Implementation Method 4
A Li-ion battery typically includes a separator and/or electrolyte between an anode and a cathode
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.