Non-Aqueous Electrolyte Composition for Low-Temperature Battery Cycling
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Solution Overview
Problem
Existing secondary batteries face a trade-off between low-temperature discharge performance and cycling performance, where improving one often deteriorates the other.
Innovation Solution
A non-aqueous electrolyte formulation comprising vinylene carbonate and a specific Formula I compound, along with additional components like cyclic carbonates, linear esters, and polycyano compounds, is used to form a robust SEI/CEI layer that enhances ion conduction and passivation, balancing low-temperature discharge and cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vinylene carbonate is used to form a dense SEI/CEI film layer, then cycling performance is improved, but ion transmission is hindered leading to increased initial impedance and reduced discharge capacity at low temperature
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing Formula I compounds with specific structural features (R groups containing fluorine or fluoroalkyl substituents). This parameter change modifies the properties of the SEI/CEI film formed, making it simultaneously dense for good cycling performance and conductive for low impedance.
Solution Approach 2:
The patent creates a composite SEI/CEI film structure by combining vinylene carbonate (which provides density and passivation) with Formula I compounds (which introduce grain boundaries for ion conduction). The synergistic interaction between these two components produces a film that exhibits both dense passivation and enhanced ion transmission, resolving the contradiction between cycling performance and initial impedance.
2Stability of the object's composition
If the SEI/CEI film layer is made denser to improve passivation, then cycling stability is enhanced, but ion conduction is reduced leading to poor low-temperature discharge performance
Solution Approach 1:
The patent applies local quality by creating heterogeneous structures within the SEI/CEI film. The Formula I compounds introduce localized grain boundaries and inorganic compounds rich in S and F elements at specific interfaces, while maintaining the overall dense structure. This local modification enables ion conduction pathways without compromising the global passivation quality.
Solution Approach 2:
The patent modifies the chemical and structural parameters of the SEI/CEI film by incorporating Formula I compounds with specific molecular structures (containing sulfur and fluorine atoms). These parameter changes transform the film from a uniformly dense structure to one with enhanced ion conduction characteristics while maintaining passivation stability.
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 formulation improves both low-temperature discharge capacity and cycling stability by forming a dense film layer with modified ion transmission, maintaining passivation while enhancing ion conduction.
Implementation Method 1
Vinylene carbonate can form a dense SEI/CEI film layer at an electrode interface during battery formation
Implementation Method 2
Formula I compound can form a lithium-containing inorganic compound rich in the S and F elements at the electrode interface
Implementation Method 3
a robust SEI/CEI layer that improves ion conduction can be synergistically formed
Data Source
AI summary
A non-aqueous electrolyte includes vinylene carbonate and Formula I compound, where based on a total mass of the non-aqueous electrolyte, a mass percentage of vinylene carbonate is A %, where 0.01≤A≤3; a mass percentage of a compound of Formula I is B %; and P=B/A, where 0.5≤P≤50.