Asymmetric Linear Ether Electrolyte for Lithium-Ion Low Temperature Performance
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Solution Overview
Problem
Lithium-iron disulfide batteries face challenges in achieving optimal electrical conductivity and low temperature performance due to limitations in electrolyte selection, including solubility issues and compatibility with lithium-based electrodes, leading to suboptimal discharge characteristics and potential safety concerns with existing solvents and salts.
Innovation Solution
A nonaqueous electrolyte comprising a solvent blend of 1,3-dioxolane, 1,2-dimethoxyethane, and 1-ethoxy-2-methoxyethane, with at least 10 vol% each, and optionally including lithium iodide as a solute, which enhances low temperature performance and maintains room temperature efficiency in lithium-iron disulfide cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional electrolyte solvents and salts are used in lithium-iron disulfide batteries, then room temperature performance can be maintained, but low temperature performance deteriorates with suboptimal discharge characteristics
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing a specific linear ether with asymmetric end groups (formula 1) containing 7-12 carbon atoms, replacing conventional symmetric ether solvents. This parameter change in molecular structure and composition enables the electrolyte to maintain optimal viscosity and ionic conductivity across a broader temperature range, particularly improving low temperature discharge characteristics while preserving room temperature performance
Solution Approach 2:
The patent creates a composite electrolyte system by combining the linear ether with asymmetric end groups (formula 1) with lithium iron disulfide cathode material and appropriate salts. This composite approach integrates multiple functional components that work synergistically: the asymmetric ether provides low temperature fluidity and wetting properties, while the salt provides ionic conductivity, resulting in an electrolyte composite that overcomes the limitations of conventional single-solvent systems
2Reliability
If solute concentration is increased to improve electrical conductivity, then conductivity increases, but solubility limitations and compatibility issues with lithium-based electrodes worsen
Solution Approach 1:
The patent changes the solvent's molecular structure parameter by using a linear ether with asymmetric end groups (formula 1) having 7-12 carbon atoms, which alters the solvent's polarity, viscosity, and solvation properties. This structural parameter change enables the solvent to dissolve higher concentrations of lithium salts while maintaining stability and compatibility with lithium-based electrodes, thereby improving electrical conductivity without sacrificing compositional stability
Solution Approach 2:
The linear ether with asymmetric end groups acts as an intermediary solvent that mediates between the lithium salt solute and the electrode materials. Its unique asymmetric structure provides optimal solvation shells for lithium ions while maintaining compatibility with the iron disulfide cathode and lithium anode, enabling high salt concentration electrolytes to function reliably without precipitation or degradation issues
3Force
If conventional ether solvents are used, then low viscosity and good wetting capability are achieved, but polarity is relatively low leading to limited ionic conductivity
Solution Approach 1:
The patent changes the polarity parameter of the ether solvent by introducing the linear asymmetric ether structure (formula 1) with 7-12 carbon atoms and specific asymmetric end groups. This structural modification increases the solvent's dipole moment and polarity compared to conventional symmetric ethers, thereby enhancing its ability to solvate lithium ions and improve ionic conductivity while preserving the low viscosity and good wetting capabilities inherent to ether solvents
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 solution significantly improves low temperature performance, potentially doubling capacity at extreme low temperatures without compromising room temperature performance, and demonstrates improved discharge characteristics in lithium-iron disulfide batteries.
Implementation Method 1
A nonaqueous electrolyte comprising a solvent blend of 1,3-dioxolane, 1,2-dimethoxyethane, and 1-ethoxy-2-methoxyethane, with at least 10 vol% each, and optionally including lithium iodide as a solute
Implementation Method 2
A nonaqueous electrolyte comprising a solvent blend of 1,3-dioxolane, 1,2-dimethoxyethane, and 1-ethoxy-2-methoxyethane... which enhances low temperature performance and maintains room temperature efficiency in lithium-iron disulfide cells
Data Source
AI summary
A primary electrochemical cell and electrolyte incorporating a linear asymmetric ether is disclosed. The ether may include EME, used in combination with DIOX and DME, or have the general structural formula R1—O—CH2—CH2—O—R2 or R1—O—CH2—CH(CH3)—O—R2, where a total of at least 7 carbon atoms must be present in the compound, and R1 and R2 consist alkyl, cyclic, aromatic or halogenated groups but cannot be the same group (i.e., R1≠R2).