NASICON Sodium Cathode Voltage and Capacity
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Solution Overview
Problem
Sodium-ion batteries face challenges with low operating voltage and high capacity fade due to deficiencies in available layered sodium oxide materials, necessitating an improved sodium ion electrode material with enhanced voltage and cyclability.
Innovation Solution
A NASICON-type compound, NaxMnaMb(PO4−δ)3, is developed, where M can be V, Nb, Ga, Cr, Ti, or a combination thereof, with specific stoichiometric ratios, which provides a stable three-dimensional framework for sodium ion mobility and long-term cyclability, utilizing multiple redox couples for improved specific capacity and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If layered sodium oxide materials are used, then sodium ion battery cost is reduced, but operating voltage is low and capacity fade is high
Solution Approach 1:
The patent changes the crystal structure parameter from layered to NASICON-type framework, and modifies stoichiometric parameters by doping with transition metals (V, Nb, Ga, Cr, Ti, Zr) to achieve both high voltage (3.4V average) and high capacity (up to 4 Na ions per formula unit) simultaneously
Solution Approach 2:
The patent creates composite materials by doping the NASICON framework with multiple transition metals (M = V, Nb, Ga, Cr, Ti, Zr or combinations), forming a composite structure that combines the stable NASICON framework with redox-active transition metal sites, achieving both structural stability and high voltage/capacity
2Quantity of substance
If layered sodium oxide materials are used, then sodium ion battery cost is reduced, but cyclability deteriorates due to capacity fade
Solution Approach 1:
The patent changes the structural parameter from 2D layered to 3D NASICON framework, which prevents structural collapse during cycling. The open framework structure with channels allows reversible Na ion insertion/extraction without phase transitions, achieving long-term cyclability with capacity retention above 80% after 100 cycles
Solution Approach 2:
The transition metal-doped NASICON composite structure combines the mechanically stable NASICON framework with redox-active transition metal sites, where the framework provides structural integrity during cycling while the transition metals provide reversible redox reactions, achieving both high capacity and excellent cyclability
3Power
If NASICON-type compound with transition metal doping is used, then average voltage increases to 3.4 V, but material complexity increases
Solution Approach 1:
The patent applies local quality by doping specific transition metal elements (V, Nb, Ga, Cr, Ti, Zr) at specific sites within the NASICON framework. The transition metals occupy specific crystallographic positions (e.g., M1, M2, M3 sites) where they provide localized redox activity, enabling high voltage (3.4V average) while maintaining the overall simplicity of the NASICON structure
Solution Approach 2:
The patent achieves universality by using multiple transition metals that all contribute to the same function (providing redox couples for high voltage). The NASICON framework itself provides multiple functions: structural stability, ion transport channels, and hosting sites for transition metals, reducing the need for additional components and simplifying the overall material design
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 compound achieves reversible sodium ion intercalation at high voltage with desirable capacity retention, increasing average voltage to 3.4 V and providing improved specific energy and energy density, while maintaining structural stability during cycling.
Implementation Method 1
utilizing multiple redox couples for improved specific capacity and energy density
Data Source
AI summary
A compound of Formula I:NaxMnaMb(PO4−δ)3 (I)wherein M is V, Nb, Ga, Cr, Ti, Zr, or a combination thereof, a is equal to or greater than 0.8 to equal to or less than 1.5, b is equal to or greater than 0.5 to equal to or less than 1.2, x is greater than 0 to equal to or less than 4, δ is equal to or greater than 0 to equal to or less than 1, and a sum of a and b is 2.