Layered Sodium Metal Oxide Composition for Stable Na-Ion Cathodes
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Solution Overview
Problem
Current sodium-ion batteries face challenges with low voltage, Jahn-Teller distortion, metal dissolution, and capacity fade due to the use of materials like Mn and Fe, and rely on expensive and toxic elements like Ni, necessitating the development of materials with high energy density, long cycling lifetimes, and structural stability using Fe3+/Fe4+ redox couple combined with low-cost dopants.
Innovation Solution
A composition with a tunable O3:P2:P3 ratio in layered sodium metal oxides, utilizing abundant elements such as Al, Mg, and Ti, to achieve high energy density, long cycle lifetimes, and good rate capability, avoiding the use of Li, Ni, Co, and minimizing Cu, while maintaining high capacities and cycling stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Fe-based materials are used in layered sodium metal oxides, then cost is reduced and sustainability is improved, but capacity fade and structural instability occur
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core contains Fe-based active material for cost and sustainability, while the shell contains protective coating layers (such as Al2O3, TiO2, or carbon) that provide structural stability and prevent degradation. This allows different regions of the material to have different functions - the core provides electrochemical activity while the shell provides protection against capacity fade
Solution Approach 2:
The patent uses composite materials by combining Fe-based sodium metal oxide with other materials such as Mn-based compounds, dopants (Al, Ti, Mg), and protective coatings to create a composite structure. This composite approach maintains the cost benefits of Fe while adding the structural stability and cycling performance of the other materials
2Ease of manufacture
If Mn-based materials are used in layered sodium metal oxides, then cost is reduced, but Jahn-Teller distortion and metal dissolution occur
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core contains Mn-based active material for cost reduction, while the shell contains protective coating layers (such as Al2O3, TiO2, or carbon) that provide structural stability and prevent Jahn-Teller distortion and metal dissolution
Solution Approach 2:
The patent uses intermediary materials such as Al, Ti, and Mg dopants that act as mediators between the Mn-based active material and the electrolyte. These dopants stabilize the crystal structure and prevent Mn dissolution without significantly reducing the electrochemical activity
3Reliability
If Ni-based materials are used in layered sodium metal oxides, then cycling stability is improved, but cost increases and toxicity increases
Solution Approach 1:
The patent applies this principle by using a small amount of Ni (or no Ni) in the core material, accepting that the Ni-containing phase may degrade faster, while the protective shell ensures overall cell longevity. This reduces the amount of expensive and toxic Ni needed while maintaining acceptable cycling stability
Solution Approach 2:
The patent uses composite materials by combining Ni-based materials with Fe-based materials and protective coatings in a core-shell or composite structure. This allows the Ni to provide initial cycling stability while the Fe and protective layers reduce cost and toxicity concerns
4Quantity of substance
If O3-phase materials are used in layered sodium metal oxides, then initial charge capacity is improved, but rate capability and cycling stability worsen
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core contains O3-phase material for high charge capacity, while the shell contains P2-phase material or conductive coatings that provide fast ion transport pathways and improve rate capability
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 composition achieves high energy density, long cycle lifetimes, and improved rate capability, enabling the production of low-cost, sustainable, and non-toxic positive electrode materials for sodium-ion batteries, optimizing the voltage window, energy density, and cycling stability.
Implementation Method 1
P2 materials show superior rate capabilities and cycling stabilities
Implementation Method 2
the high voltage Fe3+/Fe4+ redox couple has been shown to be active in these systems
Data Source
AI summary
A composition having the general formula: NaaMnbFecTidMeO2, wherein: M comprises one or more elements selected from the group consisting of aluminium, magnesium, zinc, copper, silicon, and zirconium; and wherein: 0.5<a≤1; 0.1≤b≤0.7; 0.1≤c≤0.7; 0<d≤0.3; and 0<e≤0.5, and wherein the composition is a layered sodium metal oxide material having at least a first phase and a second phase, wherein each phase is different and independently comprises one or more P2-type structures, one or more O3-type structures or one or more P3-type structures. Also described are methods of synthesizing layered sodium metal oxide materials as well as electrodes and energy storage devices including such compositions.