Ionic Liquid Electrolyte Blends for Fast-Cycling Lithium Batteries
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Solution Overview
Problem
Existing electrolytes for lithium batteries, particularly those with silicon-containing negative electrodes and sulfide-based solid electrolytes, face challenges in achieving high ionic conductivity, thermal stability, and cycling stability, which affect the batteries' charge and discharge rate capabilities.
Innovation Solution
A mixture of glyme-based and cyclic ammonium-based ionic liquids is used, with specific cation and anion components, to create an electrolyte with high ionic conductivity and low viscosity, enhancing compatibility with silicon-containing electrodes and sulfide-based solid electrolytes, thereby improving cycling stability and charge/discharge rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional electrolytes are used with silicon-containing negative electrodes and sulfide-based solid electrolytes, then the battery structure is established, but the ionic conductivity is insufficient and viscosity is high, leading to poor charge and discharge rate capabilities
Solution Approach 1:
The patent employs a composite electrolyte system combining glyme-based ionic liquid (containing lithium glyme complexes) with cyclic ammonium-based ionic liquid. This composite approach creates synergistic effects where the glyme-based component provides high lithium ion solvation and conductivity, while the cyclic ammonium component contributes to low viscosity and structural stability, collectively achieving both high ionic conductivity and fast charge/discharge rates
Solution Approach 2:
The patent optimizes specific parameters including lithium concentration (0.2-1.6 mol/L), viscosity (10-100 mPa·s), and ionic conductivity (4-10 mS/cm) by adjusting the composition ratios of cation and anion components. The glyme-to-lithium salt molar ratio is controlled at 0.7:1 to 1.2:1, and the electrolyte contains 10-40 vol% cyclic ammonium-based ionic liquid, these parameter optimizations enable simultaneous achievement of high conductivity and low viscosity
2Reliability
If high lithium concentration is used to improve ionic conductivity, then conductivity increases, but viscosity increases and mobility decreases
Solution Approach 1:
The cyclic ammonium-based ionic liquid acts as an intermediary component that mediates between the lithium-containing glyme complex and the overall electrolyte structure. It reduces the effective viscosity and enhances ion mobility without significantly compromising ionic conductivity, allowing the system to maintain both high conductivity and low viscosity simultaneously
Solution Approach 2:
The electrolyte exhibits local quality differentiation where the glyme-based ionic liquid region provides high lithium ion solvation and conductivity, while the cyclic ammonium-based ionic liquid region provides low viscosity and structural流动性. This spatial and functional differentiation allows each component to optimize its local properties without compromising overall system performance
3Temperature
If stable electrolyte composition is used to ensure thermal stability, then safety improves, but electrochemical activity and ion transport may be reduced
Solution Approach 1:
The patent merges two ionic liquid systems with complementary properties: the glyme-based ionic liquid (with lithium complexes) provides electrochemical activity and ion transport capability, while the cyclic ammonium-based ionic liquid provides thermal stability and structural robustness. The combination achieves both thermal stability and high electrochemical performance simultaneously
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 electrolyte mixture provides robust lithium ion transport pathways, ensuring high thermal stability, low volatility, and exceptional electrochemical stability, thereby enhancing the batteries' cycling stability and charge/discharge capabilities.
Implementation Method 1
an electrolyte that provides a medium for the conduction of lithium ions between the negative and positive electrodes
Implementation Method 2
ability to form a stable ionically conductive solid electrolyte interphase on the surface of the positive electrode and/or the negative electrode
Data Source
AI summary
An electrolyte for a battery that cycles lithium ions includes a glyme-based ionic liquid and a cyclic ammonium-based ionic liquid. The glyme-based ionic liquid includes substantially equimolar amounts of a cation component including a complex of lithium (Li+) and a glyme and an anion component including an arsenate ion, a phosphate ion, a sulfonylimide ion, a borate ion, and/or a chlorate ion. The cyclic ammonium-based ionic liquid includes a cation component including a piperidinium ion and/or a pyrrolidinium ion and an anion component including an arsenate ion, a phosphate ion, a sulfonylimide ion, a borate ion, and/or a chlorate ion. The electrolyte has a lithium concentration of greater than or equal to 0.2 moles per liter and less than or equal to 1.6 moles per liter. The electrolyte may be used in batteries that cycle lithium ions and that include silicon-containing electroactive negative electrode materials.