Phthalate Phosphine Anion Electrolyte for Stable SEI Formation
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining cycle capacity retention and power output at high temperatures due to the formation of a solid electrolyte interface (SEI) membrane, which increases resistance and degrades battery performance.
Innovation Solution
An electrolyte containing a lithium cation and a phthalate phosphine-type anion substituted with fluorine is used to form a stable SEI membrane on the electrode surface, minimizing resistance and maintaining power output by enhancing lithium ion permeability and chemical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid electrolyte interface (SEI) membrane is formed on the electrode surface to improve cycle properties, then cycle capacity retention is improved, but resistance inside the battery increases causing power output decrease
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing fluorinated cyclic carbonate components (fluorinated ethylene carbonate or fluorinated propylene carbonate) with specific fluorine substitution patterns. This parameter change modifies the SEI membrane formation process, resulting in a membrane with different properties that maintains lower resistance while preserving cycle stability benefits
Solution Approach 2:
The patent creates a composite electrolyte system by combining fluorinated cyclic carbonate with linear carbonate solvents (dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate) and lithium salts. This composite approach produces a SEI membrane with combined benefits: the fluorinated component provides structural stability for cycle retention, while the linear carbonate components ensure good ionic conductivity for power output
2Power
If conventional electrolyte components are used to maintain power output, then power output is maintained, but cycle capacity retention at high temperatures deteriorates
Solution Approach 1:
The patent modifies the electrolyte composition by incorporating fluorinated cyclic carbonate components at specific concentrations (1-30 wt% of total electrolyte). This parameter change enables the formation of a thermally stable SEI membrane that prevents electrolyte decomposition at high temperatures while maintaining adequate ionic conductivity for power output
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 improves the stability and cycle performance of lithium secondary batteries, maintaining superior capacity retention and power output at high temperatures by forming a protective and permeable SEI membrane.
Implementation Method 1
a solid electrolyte interface (SEI) membrane, which is formed by electrically reducing a lithium cation and a phthalate phosphine-type anion substituted at least one fluorine
Data Source
AI summary
The present specification provides an electrolyte including a phthalate phosphine-type anion, an additive for a secondary battery including the electrolyte, and a secondary battery including the additive.