Lithium Iron Oxide Cathode Reversible Anionic Redox
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Solution Overview
Problem
Conventional lithium-ion battery cathodes rely exclusively on transition metal cations for redox reactions, limiting capacity and energy density, and face challenges in developing anionic-redox-based cathodes with reversible oxygen redox due to irreversible O2 gas release.
Innovation Solution
Lithium iron oxides with the formula Li5-2α-xFeO4-α, where 0≤x≤1 and 0<α<2, are used in the cathode, enabling reversible anionic and cationic redox reactions at the same potential with minimal O2 generation by limiting charging voltage to prevent irreversible delithiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional cathode materials use only transition metal cations for redox reactions, then the battery structure is simple and easy to manufacture, but the specific capacity and energy density are limited
Solution Approach 1:
The patent changes the redox mechanism from cationic only to anionic-cationic coupled redox by modifying the electrochemical parameters. Specifically, it enables oxygen redox reactions in Li-excess layered oxide cathodes by controlling the charging voltage to remain below the oxygen evolution threshold, allowing O2- ions to participate in redox reactions and significantly increasing the specific capacity beyond the limitations of transition metal cations alone
Solution Approach 2:
The patent creates a composite redox system where both anionic (oxygen) and cationic (transition metal) redox reactions occur simultaneously in the same cathode material. This composite approach combines the high capacity potential of anionic redox with the structural stability provided by cationic redox, achieving enhanced energy density while maintaining manufacturability
2Quantity of substance
If anionic redox is enabled in cathode materials, then the specific capacity and energy density are boosted, but irreversible O2 gas release occurs due to oxygenate instability
Solution Approach 1:
The patent carefully controls the electrochemical potential window by limiting the charging voltage to remain below the threshold for oxygen evolution. This parameter control allows anionic redox reactions to proceed reversibly without triggering irreversible O2 gas release, thereby maintaining both high capacity and good cycle performance
Solution Approach 2:
The patent uses the crystal lattice structure of the Li-excess layered oxide as an intermediary environment that stabilizes the oxygenate species (O- or On2-) generated during anionic redox. The lattice provides a confining environment that prevents oxygenate decomposition and O2 gas evolution, enabling reversible oxygen redox reactions
3Quantity of substance
If Li2O with anti-fluorite structure is used to maximize anionic redox, then oxygen redox capacity is maximized, but the material requires catalysts and shows poor electronic conductivity
Solution Approach 1:
The patent combines Li-excess layered oxide structure with transition metal cations to create a composite material that maintains the high anionic redox capacity of Li2O-like structures while incorporating transition metal layers that provide intrinsic catalytic activity and electronic conductivity, eliminating the need for external catalysts
Solution Approach 2:
The patent creates local regions with different functionalities within the cathode structure. The Li-excess layers provide high anionic redox capacity while the transition metal layers provide catalytic activity and electronic conductivity. This local quality differentiation allows the material to overcome the inherent deficiencies of pure Li2O while maximizing oxygen redox capacity
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 approach achieves high specific capacity and cyclability with minimal O2 gas release, maintaining battery performance and extending the life of lithium-ion batteries.
Implementation Method 1
These materials store and release electrical energy when Li ions are extracted and inserted with charge compensation by redox reactions of the TM cations, respectively
Implementation Method 2
Phase conversion of LFO during electrochemical cycling
Data Source
AI summary
Cathode materials for lithium ion batteries, lithium ion batteries incorporating the cathode materials, and methods of operating the lithium ion batteries are provided. The materials, which are composed of lithium iron oxides, are able to undergo reversible anionic and cationic redox reactions with no O2(g) generation.