Sodium Battery Electrolyte Composition for Low-Temperature Conductivity
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Solution Overview
Problem
The performance of existing electrolytic solutions in secondary batteries is inadequate for low-temperature applications, leading to poor ionic conductivity, cycle performance, and coulombic efficiency, limiting their use in energy storage systems and electric devices.
Innovation Solution
An electrolytic solution for sodium secondary batteries comprising sodium trifluoromethanesulfonate and specific solvents with controlled carbon atom and structural unit configurations, along with balanced sodium salt and solvent ratios, enhances low-temperature ionic conductivity and cycle performance, and includes additional sodium salts and solvents to improve room-temperature performance and inhibit overcharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional electrolytic solutions are used, then room-temperature performance is maintained, but low-temperature ionic conductivity deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing specific additives (cyclic carbonate and chain carbonate) and adjusting their proportions. This parameter modification enables the electrolyte to maintain appropriate viscosity and ionic conductivity across a wide temperature range from -30°C to room temperature, resolving the contradiction between low-temperature performance and overall reliability
Solution Approach 2:
The patent creates a composite electrolyte system by combining multiple components: lithium salt, cyclic carbonate solvent, chain carbonate solvent, and specific additives. This composite structure leverages the complementary properties of each component - the cyclic carbonate provides high dielectric constant for salt dissolution, while the chain carbonate provides low viscosity for ion mobility, achieving both low-temperature conductivity and stable cycle performance
2Reliability
If electrolyte composition is optimized for low-temperature conductivity, then ionic conductivity improves, but viscosity control becomes difficult
Solution Approach 1:
The patent precisely controls the compositional parameters within specific ranges: cyclic carbonate 10-40%, chain carbonate 60-90%, with additional additives at 0.1-5%. This parameter optimization balances the competing requirements - enough cyclic carbonate to maintain salt solubility and enough chain carbonate to keep viscosity low, achieving both high ionic conductivity and appropriate viscosity for stable operation
3Reliability
If sodium salt concentration is increased, then ionic conductivity improves, but solubility at low temperature deteriorates
Solution Approach 1:
The patent uses a composite solvent system where cyclic carbonate and chain carbonate work synergistically. The cyclic carbonate component provides high dielectric constant to enhance salt solubility through strong solvation, while the chain carbonate component maintains low viscosity for ion mobility. This composite approach allows achieving both high ionic conductivity and adequate solubility at low temperatures
Solution Approach 2:
The patent optimizes the sodium salt concentration within a specific range (0.5-2.0 mol/L) and adjusts the solvent composition ratios to match. This coordinated parameter change ensures that the electrolyte maintains optimal solubility and conductivity characteristics across the operating temperature range, preventing salt precipitation at low temperatures while maintaining high ionic conductivity
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 achieves excellent low-temperature ionic conductivity, cycle performance, and coulombic efficiency, enabling the electrolytic solution to maintain performance down to -30°C and improve battery safety and efficiency across varying temperatures.
Implementation Method 1
The ethylene oxygen group in the first solvent can coordinate with the sodium ion in sodium trifluoromethanesulfonate. Controlling the number of carbon atoms and the number of repeated structural units n between two adjacent oxygens in the first solvent facilitates the chelate coordination of the first solvent with the sodium ion in sodium trifluoromethanesulfonate to form a relatively stable solvation structure
Data Source
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AI summary
An electrolyte, a sodium secondary battery and an electric device. The electrolyte comprises a first sodium salt and a first solvent, wherein the first sodium salt comprises sodium trifluoromethanesulfonate, and the first solvent has a structure as shown in formula I, with the mass ratio of the first sodium salt to the first solvent being 0.01-0.4. The electrolyte has a good low-temperature ionic conductivity, which is beneficial for improving the low-temperature cycling performance and low-temperature coulombic efficiency of the battery.