Lithium-Ion Battery Electrolyte Solvents for Low-Temperature Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion batteries for automotive applications require electrolyte materials that provide high solubility, chemical stability, a large electrochemical stability window, low viscosity, and performance over a wide temperature range, including low temperatures, while also meeting safety and cost criteria, which existing solvents fail to adequately meet.
Innovation Solution
The use of γ-valerolactone, methyl isobutyryl acetate, 2-methoxyethyl acetate, 2-ethoxyethyl acetate, and diethyl oxalate as principal solvent constituents in lithium-ion battery electrolytes, combined with lithium hexafluorophosphate, offering improved low-temperature performance and stability, and potentially mixed with carbonate solvents or gel components for enhanced conductivity and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional solvents like propylene carbonate are used in lithium-ion battery electrolytes, then the electrolyte provides adequate electrochemical stability, but the low-temperature performance and conductivity are insufficient
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte solvent by introducing esters with specific molecular structures (γ-valerolactone, methyl isobutyryl acetate, 2-methoxyethyl acetate, 2-ethoxyethyl acetate, or diethyl oxalate) that have lower viscosity and different intermolecular forces compared to traditional carbonates, thereby improving low-temperature ionic conductivity while maintaining electrochemical stability
Solution Approach 2:
The patent creates a composite electrolyte system by combining the specified ester solvents with lithium salts (such as LiPF6, LiBF4, LiClO4, or LiCF3SO3) at specific concentrations (0.5-2.0 M), forming a composite material that integrates the benefits of both components: the ester provides low-temperature performance and the lithium salt provides ionic conductivity and electrochemical stability
2Productivity
If the electrolyte solvent viscosity is reduced to improve low-temperature performance, then the ionic conductivity improves, but the electrochemical stability window may be reduced
Solution Approach 1:
The patent carefully selects esters with specific molecular weight and structural parameters that balance viscosity and stability. The chosen esters (γ-valerolactone, methyl isobutyryl acetate, 2-methoxyethyl acetate, 2-ethoxyethyl acetate, or diethyl oxalate) have molecular structures that provide low viscosity for good ionic conductivity while their functional groups (lactone ring, ester groups) maintain electrochemical stability through strong Li+ coordination and resistance to oxidation
Solution Approach 2:
The patent utilizes the local chemical environment created by the ester molecules around lithium ions, where the carbonyl oxygen atoms provide localized high-electron-density regions that strongly coordinate Li+, facilitating ion transport while the overall molecular structure maintains electrochemical inertness in the stability window
3Object-affected harmful factors
If conventional electrolyte compositions are used to ensure safety, then the flash point is adequate, but the low-temperature operational performance deteriorates
Solution Approach 1:
The patent changes the physical parameters of the electrolyte by selecting esters with inherently high flash points (all specified esters have flash points above 37°C, with many exceeding 100°C) and low melting points (below 20°C), thereby simultaneously improving safety and low-temperature performance through molecular structure selection rather than additive formulations
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
These solvent compounds provide a wide electrochemical stability window, high conductivity, and chemical stability, especially at low temperatures, surpassing the performance of traditional solvents like propylene carbonate, ensuring reliable operation in automotive applications.
Implementation Method 1
lithium ions are removed from the cathode material as the oxidation state of the transition metal component (M) of the cathode increases
Implementation Method 2
Lithium ions are inserted in the cathode during reduction at the cathode (cell discharging) as the oxidation state of the transition metal component is lowered
Implementation Method 3
The electrolyte in a lithium-ion cell may be liquid, comprising a non-aqueous solvent in which solid lithium salts, such as lithium hexafluorophosphate (LiPF6), are dissolved in an organic solvent
Data Source
AI summary
A rechargeable lithium-ion battery includes an anode, a cathode and an electrolyte containing one or more dispersed lithium salts. The electrolyte is composed of one or more solvent materials. A principal solvent constituent compound is at least one of γ-valerolactone, methyl isobutyryl acetate, 2-methoxyethyl acetate, 2-ethoxyethyl acetate, and diethyl oxalate.