Lithium Battery Electrolyte Low Temperature Ionic Conductivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining high ionic conductivity and low viscosity at low temperatures, leading to deteriorated discharge characteristics and increased internal resistance.
Innovation Solution
An electrolyte composition comprising 10 to 50% cyclic carbonate compounds and 50 to 90% linear ester compounds, specifically with ethyl propionate and propyl propionate, is used to enhance ionic conductivity and reduce viscosity, particularly at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cyclic carbonate compounds are used to achieve high dielectric constant and stable SEI layer formation, then battery stability is improved, but ionic conductivity decreases and viscosity increases at low temperature
Solution Approach 1:
The patent combines cyclic carbonate compounds (EC, PC) with linear carbonate compounds (DMC, DEC, EMC) and propionate compounds (MP, PP) in specific ratios. This merging of different solvent types with complementary properties resolves the contradiction by achieving both stability from cyclic carbonates and low-temperature ionic conductivity from linear carbonates and propionates
Solution Approach 2:
The patent optimizes the compositional parameters of the electrolyte solvent system, specifically controlling the weight ratios of cyclic carbonate (10-50%), linear carbonate (40-80%), and propionate (10-40%) compounds. By adjusting these parameters, the electrolyte achieves both high stability and improved ionic conductivity at low temperatures
2Manufacturing precision
If linear carbonate compounds or propionate compounds are used to reduce viscosity and improve ionic conductivity, then low temperature performance is improved, but discharge characteristics deteriorate at high rate discharge
Solution Approach 1:
The patent merges linear carbonate compounds (which provide low viscosity and good ionic conductivity) with cyclic carbonate compounds (which provide stability and SEI formation) and propionate compounds (which further reduce viscosity). This combination ensures both low-temperature performance and high-rate discharge characteristics are maintained
Solution Approach 2:
The electrolyte solvent system is designed as a composite material containing three types of compounds: cyclic carbonate (10-50%), linear carbonate (40-80%), and propionate (10-40%). This composite approach allows the system to exhibit both low viscosity for good ionic conductivity and sufficient stability for high-rate discharge performance
3Manufacturing precision
If solvent composition is changed to improve low temperature ionic conductivity, then viscosity decreases, but internal resistance increases and discharge characteristics deteriorate
Solution Approach 1:
The patent carefully controls the compositional parameters within specific ranges: cyclic carbonate (10-50%), linear carbonate (40-80%), and propionate (10-40%). This parameter optimization ensures viscosity is reduced for low-temperature flowability while maintaining sufficient ionic conductivity and stability to prevent excessive internal resistance
Solution Approach 2:
The electrolyte uses a composite solvent system where cyclic carbonate provides structural stability and SEI formation, linear carbonate provides low viscosity and high ionic conductivity, and propionate compounds further enhance low-temperature fluidity. The synergistic effect of this composite material reduces viscosity without compromising reliability
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 electrolyte achieves ionic conductivity of 5.5 mS/cm or higher and viscosity of 4.0 cP or lower at -10°C, improving low-temperature performance and electrochemical characteristics.
Implementation Method 1
cyclic carbonate compounds such as ethylene carbonate have a high dielectric constant and play an essential role in realizing battery performance, for example, form an SEI layer during charge/discharge
Implementation Method 2
the non-aqueous electrolyte acts as a medium through which lithium ions migrate between the negative electrode and the positive electrode
Implementation Method 3
As viscosity of the electrolyte decreases, ions migrate more freely in the electrolyte and ionic conductivity thus increases
Data Source
AI summary
Disclosed are an electrolyte for lithium secondary batteries including 10 to 50% by weight of a cyclic carbonate compound, and 50 to 90% by weight of a linear ester compound, based on the total weight of a non-aqueous solvent, wherein a content of ethyl propionate of the linear ester compound is 20 to 60% by weight, based on the total weight of the non-aqueous solvent, and a lithium secondary battery including the electrolyte and exhibiting superior low-temperature characteristics.