Low-Temperature Battery Electrolyte With Reduced EC Content
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Solution Overview
Problem
Lithium-ion batteries face significant performance losses at sub-zero temperatures due to carbonate-based liquid electrolytes, limiting their deployment in extreme environments, and existing solutions like external battery warming systems are inefficient for discharge operations.
Innovation Solution
A novel electrolyte system for dual-graphite batteries that combines a primary ester solvent with a low percentage of fluoroethylene carbonate, enhancing electrochemical stability and ionic conductivity at low temperatures, thereby improving capacity retention and voltage retention during discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If carbonate-based liquid electrolytes are used in lithium-ion batteries, then the batteries can operate under mild conditions with relatively high specific energy, but they suffer severe performance losses at sub-zero temperatures
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by replacing carbonate-based solvents with ester-based solvents (methyl propionate, methyl butyrate, ethyl propionate, ethyl butyrate) that have lower melting points and different solvation properties. This parameter change enables the electrolyte to maintain liquid state and ionic conductivity at sub-zero temperatures, resolving the contradiction between operating temperature range and power density retention
Solution Approach 2:
The patent creates a composite electrolyte system by combining ester-based solvents with specific additives (1,3-propanesultone, vinylene carbonate) and lithium salts. This composite formulation synergistically improves both the low-temperature fluidity and the electrochemical stability, achieving reliable power delivery across wide temperature ranges while maintaining high specific energy
2Reliability
If low melting-point solvents and novel salt additives are employed to minimize resistances, then low-temperature discharge performance improves, but electrochemical stability deteriorates
Solution Approach 1:
The patent applies local quality by using small amounts (0.1-5% by weight) of specific additives (1,3-propanesultone and vinylene carbonate) within the ester-based electrolyte system. These additives locally modify the electrode interface properties to enhance low-temperature kinetics without compromising the bulk electrolyte's electrochemical stability. The ester-based solvent maintains stability while the additives improve discharge performance at low temperatures
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 novel electrolyte system achieves an eleven-fold increase in capacity retention at -60°C for dual-graphite batteries compared to industry-type graphite∥LiCoO2 full-cells, demonstrating superior kinetics and maintaining 67.5% capacity retention with higher voltage retention, outperforming conventional electrolytes.
Implementation Method 1
The negative electrode is a graphite negative electrode, and the electrolyte stabilizes a solid-electrolyte-interface (SEI) on the graphite negative electrode
Implementation Method 2
which facilitates the transport of ions between electrodes and governs a set of discrete cell impedance contributors
Implementation Method 3
1) migration through the solid-electrolyte-interface (SEI), 2) bulk ionic transport, and 3) charge-transfer, which is dominated by Li+ de-solvation at the positive electrode interface
Data Source
AI summary
Lithium batteries (LBs) are formed using an electrolyte including a lithium salt in an ester primary solvent with a low percentage of about 5% to about 30% of an ethylene carbonate (EC). The batteries exhibit high electrochemical stability and ionic conductivity at low temperatures.