Sodium Battery Electrolyte Composition for Low-Temperature Ion Transport
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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.
Innovation Solution
An electrolytic solution for sodium secondary batteries comprising sodium trifluoromethanesulfonate and specific solvents with controlled mass ratios and structural units, along with additional sodium salts and solvents, to enhance low-temperature ionic conductivity and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolytic solutions are used, then the battery can operate at room temperature, but the low-temperature ionic conductivity deteriorates significantly
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolytic solution by introducing specific additives (cyclic carbonate and chain carbonate esters) with defined molecular structures and ratios. This modifies the solvation structure and ionic conductivity of the electrolyte, enabling it to maintain high performance at low temperatures without sacrificing room-temperature operation
Solution Approach 2:
The patent creates a composite electrolytic solution system by combining multiple components: cyclic carbonate ester, chain carbonate ester, and lithium salt. This composite approach 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 superior low-temperature ionic conductivity
2Reliability
If the electrolytic solution is optimized for low-temperature performance, then ionic conductivity improves, but the viscosity increases adversely
Solution Approach 1:
The patent optimizes the molecular structure parameters of the carbonate esters and controls their ratio in the electrolytic solution. By selecting appropriate chain lengths and ether group positions, the solution achieves a balance between solvation capability and fluidity, maintaining low viscosity even at low temperatures while ensuring high ionic conductivity
3Reliability
If the concentration of sodium salt is increased to improve ionic conductivity, then the low-temperature performance improves, but the solubility limit is exceeded causing precipitation
Solution Approach 1:
The patent modifies the solvent properties by introducing cyclic and chain carbonate esters with specific molecular structures. These solvents provide both high dielectric constants for salt dissociation and appropriate solvation energies, dramatically increasing the solubility of sodium trifluoromethanesulfonate. This enables the use of high concentrations of sodium salt (improving ionic conductivity) without exceeding the solubility limit and causing precipitation
4Reliability
If the number of repeated structural units in the solvent is increased to enhance coordination, then the solvation stability improves, but the viscosity increases
Solution Approach 1:
The patent precisely controls the molecular structure parameters of the carbonate ester solvents, specifically the number of repeated structural units and the position of ether groups. By optimizing these parameters, the solution achieves effective chelate coordination with sodium ions (forming stable 5-membered or 6-membered rings) while preventing excessive chain entanglement that would increase viscosity. This balances solvation stability with fluidity for low-temperature operation
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 provides excellent low-temperature ionic conductivity, cycle performance, and coulombic efficiency, maintaining performance from 0°C to −30°C, and inhibiting overcharge.
Implementation Method 1
The ethylene oxygen group in the first solvent can coordinate with the sodium ion in sodium trifluoromethanesulfonate
Implementation Method 2
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
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.