Non-aqueous Electrolyte Solution for Low-Temperature Battery Performance
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Solution Overview
Problem
Existing non-aqueous electrolyte solutions for lithium ion secondary batteries fail to maintain stable performance at extremely low temperatures, such as −30° C. or lower, due to the lack of consideration for low temperature regions in previous compositions.
Innovation Solution
A non-aqueous electrolyte solution is developed using a blend of cyclic carbonate-based, linear carbonate-based, and ester-based solvents, specifically ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and ethyl propionate, which improves battery performance and maintains high ionic conductivity at temperatures below −40° C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional non-aqueous electrolyte solutions are used, then battery performance is acceptable at normal temperatures, but battery performance becomes unstable at extremely low temperatures (−30°C or lower)
Solution Approach 1:
The patent applies parameter changes by modifying the electrolyte solution composition to achieve optimal low-temperature performance. Specifically, it sets the cyclic carbonate-based solvent content at 10-30 vol%, ester-based solvent at 5-20 vol%, and linear carbonate-based solvent at 65-85 vol%, with LiPF6 electrolyte concentration at 0.5-2.0 mol/L. These parameter optimizations enable stable battery operation at extremely low temperatures while maintaining acceptable performance at normal temperatures.
Solution Approach 2:
The patent employs composite materials by combining multiple solvent types (cyclic carbonate-based, linear carbonate-based, and ester-based solvents) with electrolyte (LiPF6) in specific proportions. This composite electrolyte system leverages the complementary properties of each component: cyclic carbonates provide high dielectric constant, linear carbonates provide low viscosity, and esters enhance low-temperature fluidity, achieving synergistic effect for stable low-temperature battery performance.
2Reliability
If ester-based and carbonate-based solvents are simply mixed, then the electrolyte solution shows improved ionic conductivity, but it fails to maintain stable performance in extremely low temperature regions
Solution Approach 1:
The patent resolves this contradiction by precisely controlling the composition parameters within optimal ranges rather than using arbitrary mixtures. The cyclic carbonate-based solvent is limited to 10-30 vol% (not higher to avoid excessive viscosity), ester-based solvent to 5-20 vol% (not higher to maintain flash point), and linear carbonate-based solvent to 65-85 vol%. These constrained parameter ranges simplify the composition design while ensuring reliable low-temperature performance.
3Reliability
If the electrolyte solution is optimized for low temperature performance, then ionic conductivity improves, but flash point may decrease
Solution Approach 1:
The patent balances ionic conductivity and flash point by optimizing the electrolyte concentration and solvent ratios. The LiPF6 concentration is set at 0.5-2.0 mol/L, and the ester-based solvent is limited to 5-20 vol% to maintain flash point above 21°C while ensuring sufficient ionic conductivity through the combined effect of all solvent components.
Solution Approach 2:
The patent uses composite materials to simultaneously achieve high ionic conductivity and safe flash point. The multi-component electrolyte system (cyclic carbonate + linear carbonate + ester) creates a balanced composition where each component contributes to overall performance: cyclic carbonates enhance dielectric constant for ion dissolution, linear carbonates reduce viscosity for ion mobility, and esters improve low-temperature fluidity, while the combined system maintains adequate flash point safety.
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 solution enables stable battery performance, high ionic conductivity, and suitable flash points, allowing the battery to function effectively as a power source for vehicles in cold weather regions.
Implementation Method 1
the ionic conductivity of a non-aqueous electrolyte solution in low temperature regions by suppressing an increase in viscosity of the electrolyte solution
Implementation Method 2
a non-aqueous electrolyte solution that contains a non-aqueous solvent and an electrolyte
Data Source
AI summary
The present teaching provides a non-aqueous electrolyte secondary battery provided with a non-aqueous electrolyte solution having a composition able to achieve high battery performance even in an extremely low temperature region (for example, −30° C. or lower). The non-aqueous electrolyte solution disclosed herein contains, as non-aqueous solvents, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and ethyl propionate (EP), and when the total volume of the non-aqueous solvents is 100 vol. %, the content of EC is 20 to 30 vol. %, the content of PC is 5 to 10 vol. %, the content of EP is 5 to 10 vol. %, and the content of DMC+EMC is 50 to 70 vol. %.