Non-Aqueous Electrolyte Composition for Low-Impedance Li-Ion Cycling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing non-aqueous electrolytes in secondary batteries suffer from poor thermal stability, high interfacial impedance, and irreversible lithium ion consumption, leading to reduced cycle, storage, and kinetic performance.
Innovation Solution
A non-aqueous electrolyte comprising specific lithium salts with controlled mass contents and ratios, along with a solvent system, forms a dense, stable, and low-impedance interfacial film on both positive and negative electrodes, enhancing thermal stability and ionic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional non-aqueous electrolytes are used, then ionic conductivity is maintained, but thermal stability deteriorates and interfacial impedance increases
Solution Approach 1:
The patent uses a composite electrolyte system combining lithium bis(fluorosulfonyl)imide (LiFSO2) salt with fluorinated cyclic carbonate solvents (FEC, FDMC) and non-fluorinated cyclic carbonate solvents (EC, DMF). This composite approach creates synergistic effects where the fluorinated components provide thermal stability while the combination forms a balanced interfacial film that reduces impedance without sacrificing conductivity.
Solution Approach 2:
The patent optimizes specific parameter ranges: LiFSO2 content at 5-20 mass%, fluorinated cyclic carbonate content at 5-30 mass%, and non-fluorinated cyclic carbonate content at 65-90 mass%. These parameter adjustments ensure the electrolyte forms an optimal interfacial film composition that simultaneously improves thermal stability and reduces interfacial impedance while maintaining ionic conductivity.
2Reliability
If electrolyte additives are increased to improve interfacial film formation, then cycle performance improves, but irreversible lithium ion consumption increases
Solution Approach 1:
The patent precisely controls the content of LiFSO2 (5-20 mass%) and fluorinated cyclic carbonate (5-30 mass%) to optimize interfacial film formation. This parameter optimization ensures sufficient film coverage for good cycle performance while minimizing excess additive consumption that would lead to irreversible lithium ion loss. The balanced composition achieves film formation efficiency without over-consumption.
3Temperature
If fluorinated lithium salts are used to improve thermal stability, then thermal performance improves, but interfacial impedance increases
Solution Approach 1:
The patent combines fluorinated LiFSO2 salt with a dual-component solvent system (fluorinated cyclic carbonate + non-fluorinated cyclic carbonate). The fluorinated salt provides thermal stability through its chemically stable anion, while the mixed solvent system ensures low interfacial impedance by forming a balanced SEI film. The non-fluorinated cyclic carbonate component specifically addresses the impedance issue by providing good wettability and film-forming properties that counterbalance the potential impedance increase from fluorinated salts.
Solution Approach 2:
The patent applies different functional components at different levels: the fluorinated LiFSO2 salt provides localized thermal stability at the molecular level, while the mixed solvent system provides localized film-forming properties at the interfacial level. This local quality differentiation allows thermal stability and low impedance to be achieved through different mechanisms acting at different locations within the electrolyte system.
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 simultaneous improvements in cycle, storage, and kinetic performance by forming a synergistic interfacial film that reduces irreversible lithium ion consumption and internal resistance.
Implementation Method 1
Non-aqueous electrolyte plays a role of conducting ions between the positive and negative electrodes
Implementation Method 2
the non-aqueous electrolyte can also passivate the aluminum foil collector and form a dense, stable and low-impedance interfacial film on the surface of the positive active material and the negative active material
Data Source
Figure 1~3
Figure 4~6
AI summary
The present application provides a non-aqueous electrolyte and a secondary battery, a battery module, a battery pack and an electrical device containing the same. The non-aqueous electrolyte includes an electrolyte salt and a non-aqueous solvent, wherein the electrolyte salt comprise a first lithium salt, a second lithium salt and a third lithium salt, and the content A1 of the first lithium salt, the content A2 of the second lithium salt and the content A3 of the third lithium salt, based on the total mass of said non-aqueous electrolyte, satisfy that: A1+A2+A3 is below 1%, A1/A2 is from 0.016 to 40, and A1/ (A2+A3) is from 0.006 to 13.5. This application enables the secondary battery to have good cycle performance, storage performance and kinetic performance at the same time.