Lithium Ion Electrolyte Low Temperature Performance
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Solution Overview
Problem
Lithium ion rechargeable batteries exhibit limited performance at low temperatures due to viscous electrolyte solutions and surface film resistance, which affects conductivity and cycle life, making them unsuitable for applications requiring operation below -30°C, such as NASA missions and low earth orbit satellites.
Innovation Solution
Development of lithium ion electrolytes comprising a mixture of ethylene carbonate, ethyl methyl carbonate, and high molecular weight ester cosolvents like methyl propionate, ethyl propionate, and ethyl butyrate, which improve ionic conductivity and stability across a wide temperature range from -60°C to 60°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte solutions are used, then the battery operates well at ambient temperatures, but the electrolyte becomes viscous and freezes at low temperatures, resulting in poor conductivity
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing ester cosolvents (methyl propionate, ethyl propionate, ethyl butyrate) with specific molecular weights and physical properties. These esters have lower freezing points and lower viscosities compared to conventional carbonate solvents, allowing the electrolyte to remain fluid and conductive at temperatures as low as -60°C while maintaining ambient temperature performance.
Solution Approach 2:
The patent creates a composite electrolyte system by blending multiple components: ethylene carbonate (EC) for high dielectric constant and lithium salt solubility, ethyl methyl carbonate (EMC) for low viscosity and wide liquid range, and high molecular weight ester cosolvents for low freezing point and enhanced low-temperature conductivity. This composite approach synergistically combines the advantages of each component to achieve broad temperature range operation.
2Use of energy by moving object
If the battery is designed for high specific energy, then the energy density improves, but the low temperature capacity and rate capability are limited
Solution Approach 1:
The patent optimizes the electrolyte composition parameters to achieve a balance between energy density and low-temperature performance. By adjusting the ratios of EC, EMC, and ester cosolvents, along with lithium salt concentration, the electrolyte maintains high ionic conductivity at low temperatures while supporting high specific energy batteries. The ester cosolvents specifically enhance lithium ion mobility at low temperatures without compromising the energy storage capacity of the electrodes.
3Duration of action of stationary object
If conventional electrolytes are used, then the cell design is simple, but the cycle life and stability at extreme temperatures are insufficient
Solution Approach 1:
The patent develops a multi-component electrolyte composite consisting of EC, EMC, and high molecular weight ester cosolvents. This composite formulation enhances cycle life and stability at extreme temperatures through synergistic interactions: EC provides stable SEI formation, EMC ensures low viscosity and wide liquid range, and ester cosolvents prevent freezing and maintain conductivity at low temperatures. The composite approach extends battery operational life from conventional limits to over 500 cycles while maintaining performance from -60°C to +60°C.
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 electrolytes enhance discharge performance, rate capability, and cycle life at low temperatures, delivering up to six times the capacity of baseline electrolytes and supporting aggressive rates, while maintaining high temperature resilience, thus addressing the limitations of existing lithium ion batteries.
Implementation Method 1
an electrolyte consisting of a lithium salt dissolved in one or more organic solvents
Implementation Method 2
the physical properties of the electrolyte, such as conductivity (lithium ion mobility in the electrolyte solution), melting point, viscosity
Implementation Method 3
capable of operation at temperatures as low as −40° C. Mars penetrators, which can penetrate deep into the Martian surface, require operation at temperatures less than −60° C.
Data Source
AI summary
There is provided in one embodiment of the invention an electrolyte for use in a lithium ion electrochemical cell. The electrolyte comprises a mixture of an ethylene carbonate (EC), an ethyl methyl carbonate (EMC), an ester cosolvent, and a lithium salt. The ester cosolvent comprises methyl propionate (MP), ethyl propionate (EP), methyl butyrate (MB), ethyl butyrate (EB), propyl butyrate (PB), or butyl butyrate (BB). The electrochemical cell operates in a temperature range of from about −60 degrees Celsius to about 60 degrees Celsius. In another embodiment there is provided a lithium ion electrochemical cell using the electrolyte of the invention.