LiFSI-CPME Electrolyte for Low-Temperature Fast-Charging Cells
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Solution Overview
Problem
Lithium-ion batteries face challenges in maintaining performance at low temperatures and fast charging due to issues with electrolyte conductivity, SEI layer formation, and solvent freezing.
Innovation Solution
An electrolyte composition comprising lithium bifluorosulphonyl imide (LiFSI) dissolved in cyclopentyl methyl ether (CPME) forms an anion-derived solvation structure that reduces covalent bond strength, leading to a robust LiF-rich SEI layer and improved low-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional carbonate electrolytes (EC, PC, DEC) are used in lithium-ion batteries, then good cyclability at room temperature is achieved, but low temperature performance deteriorates due to solvent freezing and high viscosity
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by replacing conventional carbonate solvents (EC, PC, DEC) with ether-based solvents (CPME, DME, TEGDME) and adjusting the lithium salt concentration. This parameter change fundamentally alters the physical properties of the electrolyte, including freezing point and viscosity, enabling operation at low temperatures while maintaining cyclability through the formation of a stable SEI layer
Solution Approach 2:
The patent creates a composite electrolyte system combining ether-based solvents with specific lithium salts (LiFSO3, LiPF6) and cyclic carbonates (GBL, GVL). This composite approach leverages the complementary properties of each component: ether solvents provide low freezing point and good low-temperature ionic conductivity, while cyclic carbonates contribute to stable SEI formation, achieving both low-temperature performance and cyclability
2Productivity
If fast charging is implemented to reach 80% capacity in fifteen minutes, then charging speed is improved, but charge transfer resistance at the electrode/electrolyte interface increases
Solution Approach 1:
The patent changes the electrolyte composition parameters to include ether-based solvents with high ionic conductivity and appropriate viscosity. These parameter changes reduce the charge transfer resistance at the electrode/electrolyte interface by improving Li+ ion mobility and solvation dynamics, enabling faster charging rates while maintaining electrochemical stability and charge transfer efficiency
3Reliability
If electrolyte conductivity is improved for fast charging, then charge transfer kinetics are enhanced, but SEI layer stability deteriorates
Solution Approach 1:
The patent employs a composite electrolyte formulation combining ether-based solvents (for high ionic conductivity and fast charge transfer kinetics) with cyclic carbonate additives (GBL, GVL) and lithium salts. This composite structure enables the formation of a stable SEI layer that maintains integrity during fast charging, as the cyclic carbonate components contribute to SEI formation while the ether components provide high ion mobility, resolving the contradiction between kinetics and stability
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 CPME-based electrolyte composition enhances low-temperature performance, maintaining high capacity and stability from 0°C to -40°C, with a robust SEI layer facilitating faster Li+ ion conduction and reduced charge transfer resistance.
Implementation Method 1
lithium bifluorosulphonyl imide (LiFSI) dissolved in cyclopentyl methyl ether (CPME) to form Li cations and FSI anions. The electrolyte composition has an anion-derived solvation structure
Implementation Method 2
The electrolyte composition has an anion-derived solvation structure that reduces the covalent bond strength between the Li cations and FSI anions
Implementation Method 3
leading to a robust LiF-rich SEI layer and improved low-temperature performance
Implementation Method 4
the solvent molecules are reduced on the anode surface and form the insulating SEI layer
Implementation Method 5
a robust SEI layer facilitating faster Li+ ion conduction and reduced charge transfer resistance
Implementation Method 6
maintaining high capacity and stability from 0°C to -40°C
Data Source
AI summary
Electrochemical cells and electrolyte compositions therefor. Such an electrolyte composition includes lithium bifluorosulphonyl imide (LiFSI) dissolved in cyclopentyl methyl ether (CPME) solvent. The electrolyte composition has an anion-derived solvation structure that can form a lithium fluoride (LiF) layer on an anode of an electrochemical cell. The anion-derived solvation structure may reduce the covalent bond strength between the Li cations and FSI anions.