LiFSI-HFE Electrolyte for Vanadium Sulfide Battery Cycle Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-based nonaqueous secondary batteries suffer from low charge/discharge cycle performance, needle-like lithium deposition, and safety issues, while sulfur-based cathode active materials face capacity loss during repeated cycles.
Innovation Solution
A nonaqueous secondary battery using vanadium sulfide as a cathode active material and lithium-containing compounds as an anode, with an electrolyte solution comprising lithium bis(fluorosulfonyl)imide, cyclic carbonates, and hydrofluoroether, optimized in specific molar ratios to enhance interaction and suppress lithium deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional electrolytes (carbonate esters or chain esters) are used, then basic electrochemical performance is maintained, but low-temperature discharge characteristics deteriorate and viscosity increases
Solution Approach 1:
The patent uses a composite electrolyte system combining cyclic carbonate ester (EC, PC) with chain carbonate ester (DMC, DEC) and cyclic carbonate (GBL, GVL). This composite approach leverages the high dielectric constant of cyclic carbonates to maintain ionic conductivity while the chain carbonates provide low viscosity and low-temperature fluidity, resolving the contradiction between low-temperature performance and viscosity.
Solution Approach 2:
The patent optimizes the specific gravity of the electrolyte to 1.15-1.25 and controls water content at 0.003-0.03 mass%. By adjusting these physical parameters, the electrolyte achieves improved low-temperature discharge characteristics while maintaining appropriate viscosity levels for battery operation.
2Reliability
If LiClO4 is used as electrolyte additive, then electrochemical performance is improved, but battery output becomes unstable due to oxygen evolution from LiClO4 decomposition
Solution Approach 1:
The patent removes LiClO4 from the electrolyte composition entirely, replacing it with LiPF6 as the lithium salt. This extraction eliminates the harmful oxygen evolution caused by LiClO4 decomposition while maintaining electrochemical performance through the use of LiPF6 combined with the optimized cyclic and chain carbonate ester mixture.
Solution Approach 2:
The patent employs LiPF6 as a more stable and reliable electrolyte additive that does not suffer from the decomposition issues of LiClO4. This substitution provides consistent electrochemical performance without the harmful effects of oxygen evolution, effectively replacing an unstable component with a more reliable alternative.
3Power
If battery capacity is increased to achieve high output, then power delivery improves, but heat generation increases and temperature control becomes difficult
Solution Approach 1:
The patent optimizes the electrolyte's specific gravity to 1.15-1.25 and controls water content within 0.003-0.03 mass%. These parameter adjustments improve the electrolyte's thermal stability and heat dissipation properties, allowing the battery to deliver high power output while effectively managing heat generation and maintaining temperature control.
Solution Approach 2:
The composite electrolyte system combining cyclic carbonate esters (EC, PC) with chain carbonates (DMC, DEC) and cyclic carbonates (GBL, GVL) provides both high ionic conductivity for power delivery and appropriate viscosity for heat management. This composition enables high output performance while the electrolyte's thermal properties help dissipate heat effectively.
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 a secondary battery with improved charge/discharge cycle performance and suppresses needle-like lithium deposition, maintaining high capacity and safety.
Implementation Method 1
LiPF6 is used as the electrolyte, and the electrolyte may be used in combination with a cyclic carbonate ester such as ethylene carbonate (EC) or propylene carbonate (PC), a chain carbonate ester such as dimethyl carbonate (DMC) or diethyl carbonate (DEC), or a cyclic carbonate such as γ-butyrolactone (GBL) or γ-valerolactone (GVL)
Implementation Method 2
non-aqueous secondary battery which uses LiPF6 as the electrolyte
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A nonaqueous secondary battery electrolyte solution for use in a nonaqueous secondary battery comprising vanadium sulfide as a cathode active material and a lithium-containing compound as an anode active material, the nonaqueous secondary battery electrolyte solution comprising lithium bis(fluorosulfonyl)imide (LiFSI), a cyclic carbonate, and a hydrofluoroether (HFE).