Phenazine Oligomer Cathode Material for Reversible High-Voltage Batteries
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Solution Overview
Problem
Polymer-based organic battery materials face limitations in reversibility due to dissolution in organic electrolytes and chemical bond cleavage during lithiation/delithiation, leading to efficiency losses and reduced cyclability, along with issues like low thermal stability and voltage hysteresis.
Innovation Solution
An oligomer of phenazine derivatives, specifically an N,N′-di(hetero)aryl-5,10-dihydrophenazine structure with optimized arylene or heteroarylene substitutions, is used as a high-voltage organic battery cathode material, enhancing aromaticity and molecular stability through π-LP-π bonding, and is processed by reacting 5,10-dihydrophenazine with hal-R-hal, followed by optional endcapping steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If polymer-based organic battery materials are used as cathode active material, then flexibility and redox property tunability are improved, but reversibility is worsened due to dissolution in organic electrolyte and chemical bond cleavage during lithiation/delithiation
Solution Approach 1:
The invention segments the polymer chain into controlled oligomer units with specific chain lengths (n=3-30). This segmentation reduces the overall molecular weight and size, preventing dissolution in organic electrolytes while maintaining the redox activity of individual phenazine units. The oligomer structure allows tuning of redox properties through controlled polymerization degree while avoiding the reversibility issues of high molecular weight polymers.
Solution Approach 2:
The invention creates composite structures by incorporating oligomers of phenazine derivatives with specific end-cap groups (X and Y) that can be tailored for different properties. The composite nature of the oligomer structure, combining redox-active phenazine units with stabilizing end-caps and controlled chain lengths, achieves both redox property tunability and improved reversibility by preventing both dissolution and bond cleavage.
2Adaptability or versatility
If polymer-based organic battery materials are used as cathode active material, then flexibility is improved, but thermal stability is worsened
Solution Approach 1:
By segmenting the polymer into controlled oligomer units with specific chain lengths (n=3-30), the invention maintains flexibility at the macroscopic level while improving thermal stability. The lower molecular weight of oligomers compared to high polymers reduces thermal degradation risks, and the controlled structure allows for better thermal management without sacrificing the flexibility advantage of organic materials.
3Adaptability or versatility
If polymer-based organic battery materials are used as cathode active material, then redox mechanism based on conversion reactions is improved, but voltage hysteresis is worsened
Solution Approach 1:
The invention changes the molecular weight parameter by transitioning from high molecular weight polymers to controlled oligomers with specific chain lengths (n=3-30). This parameter change reduces voltage hysteresis while maintaining the conversion reaction mechanism, as the smaller oligomer units experience less structural reorganization during lithiation/delithiation cycles, thereby reducing energy loss.
4Power
If N,N′-substituted phenazine derivatives are used to achieve two successive one-electron transfer reactions, then redox potential is improved, but molecular stability is worsened
Solution Approach 1:
The invention creates a composite oligomer structure where phenazine units with high redox potential are combined with stabilizing end-cap groups and controlled chain lengths. This composite approach allows the phenazine core to provide high redox potential for two successive one-electron transfer reactions, while the overall oligomer structure with controlled architecture maintains molecular stability during electrochemical cycling.
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 oligomer exhibits improved electrochemical performance with high redox potential, stability, and cyclability, maintaining high voltage profiles and energy density, while reducing internal shuttle effects and side reactions, making it suitable for lithium-ion, sodium, and magnesium-based batteries.
Implementation Method 1
These molecules undergo two successive one-electron transfer reactions (see FIG. 1a), thus can be categorized as p-type molecules, which usually show higher redox potential than the n-type ones.
Data Source
AI summary
The present invention relates to an oligomer-based organic battery materials, cathode active material, cathode and secondary battery comprising such material, and a process for preparing such materials.