Hetero Polycyclic Electrolyte for Lithium Battery SEI Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries face issues with high-temperature stability and low-temperature conductivity due to the instability of the SEI layer, leading to increased inner pressure and capacity deterioration, which existing solvent composition changes or additive mixtures fail to adequately address.
Innovation Solution
A nonaqueous electrolyte for lithium secondary batteries incorporating a hetero polycyclic compound, which forms a polymeric film on electrodes, stabilizes electrochemical reactions, and improves high-temperature life characteristics by suppressing metal cation elution and radical stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ethylene carbonate is used as a solvent to improve ion conductivity, then low-temperature conductivity is improved, but high-temperature stability deteriorates due to SEI layer instability and increased inner pressure
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing a hetero polycyclic compound with specific molecular structure (containing nitrogen atoms in the ring structure). This compositional parameter change enables the formation of a more stable SEI layer that maintains integrity at high temperatures while preserving ion conductivity at low temperatures, thus resolving the contradiction between low-temperature conductivity and high-temperature stability
Solution Approach 2:
The patent creates a composite electrolyte system by combining traditional carbonate solvents (ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate) with a hetero polycyclic compound. This composite approach leverages the high dielectric constant and ion solvation capability of carbonate solvents while the hetero polycyclic compound contributes to forming a stable protective film, achieving both low-temperature conductivity and high-temperature stability
2Use of energy by moving object
If the battery is left alone in a fully-charged state at high temperature, then electrochemical energy increases, but the SEI layer collapses due to thermal energy, causing side reactions and continuous gas generation
Solution Approach 1:
The hetero polycyclic compound acts as a preventive agent that forms a robust SEI layer before thermal runaway can occur. This pre-formed stable SEI layer serves as a cushioning protective barrier that prevents collapse even when the battery is left charged at high temperatures, blocking the pathway for side reactions and gas generation that would otherwise occur due to thermal energy
3Duration of action of stationary object
If a hetero polycyclic compound is added to stabilize the SEI layer, then high-temperature life characteristics are improved, but device complexity increases
Solution Approach 1:
The patent optimizes the concentration parameter of the hetero polycyclic compound in the electrolyte to achieve the desired effect with minimal addition. By carefully controlling this compositional parameter, the patent improves high-temperature life characteristics while avoiding excessive complexity in the electrolyte formulation, maintaining practical manufacturability
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 use of a hetero polycyclic compound in the nonaqueous electrolyte enhances the battery's high-temperature life characteristics and stability, preventing capacity deterioration and improving charge/discharge performance.
Implementation Method 1
a hetero polycyclic compound... which forms a polymeric film on electrodes
Implementation Method 2
forms a polymeric film on electrodes, stabilizes electrochemical reactions
Implementation Method 3
a non-aqueous electrolyte containing a proper amount of lithium salts dissolved in a mixed organic solvent... serves as a lithium ion source
Implementation Method 4
The SEI layer plays role of an ion tunnel and allows only lithium ions to pass. Due to the ion tunnel effect, the SEI layer prevents organic solvent molecules... from being intercalated
Implementation Method 5
lithium ions emitting from a cathode active material... move to an anode active material such as graphite and are intercalated between layers of the anode active material
Implementation Method 6
the electrolyte is reacted with carbon of the anode active material at the surface of the anode active material such as graphite, thereby generating compounds such as Li2CO3, Li2O and LiOH
Implementation Method 7
side reaction to continuously occur between the exposed surface of the anode and the surrounding electrolyte
Data Source
AI summary
Disclosed are a nonaqueous electrolyte for a lithium secondary battery containing a hetero polycyclic compound and a lithium secondary battery using the same.