High-Entropy Layered Oxide Cathode for Stable Sodium-Ion Oxygen Redox
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Solution Overview
Problem
Current sodium ion batteries face challenges with oxygen redox-active materials experiencing dynamic hysteresis, voltage hysteresis, oxygen release, and severe capacity fading, limiting their application due to structural deterioration and high charging voltages, which are exacerbated by the scarcity and rising cost of lithium resources.
Innovation Solution
A high-entropy layered oxide material with anion/cation covalence is developed, featuring a chemical formula Na a [Li b Mg c Ni d Mn e M f ]O 2+β, where M is a transition metal, configured to provide charge compensation through redox-action of cations and anions, ensuring structural stability and long-cycle performance by disorderly distributing transition metals, reducing the initial oxygen redox voltage to 4.2V, and using a simple preparation method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If oxygen redox-active materials are used to increase specific capacity and energy density, then energy density is improved, but structural deterioration and severe capacity fading occur due to high charging cut-off voltage
Solution Approach 1:
The patent introduces high-entropy elements (at least 5 different transition metal elements) into the layered oxide structure, fundamentally changing the material's compositional parameters. This high-entropy configuration stabilizes the crystal structure during charging/discharging cycles, enabling the material to maintain structural integrity at high voltages (4.2V or higher) while achieving high energy density through anionic redox reactions
Solution Approach 2:
The patent creates a composite material system by combining multiple transition metal elements (Ni, Mn, Co, Cu, Zn, Fe, etc.) in specific ratios within the layered oxide structure. This multi-element composite approach leverages the synergistic effects of different metals to simultaneously achieve high capacity, structural stability, and long cycle life, resolving the contradiction between energy density and reliability
2Quantity of substance
If high charging cut-off voltage (4.4V) is applied to activate lattice oxygen for higher capacity, then specific capacity is improved, but unnecessary structural deterioration and severe side reactions occur
Solution Approach 1:
The high-entropy element composition changes the electrochemical behavior of the material, enabling lattice oxygen activation and anionic redox reactions to occur at lower voltages (4.2V or lower) compared to conventional materials. This parameter change in redox potential allows achieving high specific capacity without the harmful structural deterioration associated with higher voltages
Solution Approach 2:
The high-entropy element configuration acts as a protective mechanism that preemptively stabilizes the crystal structure before charging begins. This pre-stabilization cushioning effect prevents structural deterioration and side reactions during the charging process at high voltages, allowing safe activation of lattice oxygen
3Use of energy by moving object
If lithium ion batteries are used to achieve high energy density, then energy density is improved, but resource scarcity and rising costs limit large-scale application
Solution Approach 1:
The patent replaces scarce and expensive lithium ions with abundant and inexpensive sodium ions as the charge carriers in the battery system. While sodium ion batteries traditionally have lower energy density, the high-entropy layered oxide material achieves high capacity through anionic redox, making sodium ion batteries a cost-effective alternative for large-scale energy storage applications
Solution Approach 2:
The invention changes the fundamental operating parameters of sodium ion batteries by introducing high-entropy layered oxide materials with anionic redox capability. This parameter change enables sodium ion batteries to achieve energy densities comparable to lithium ion batteries, overcoming the resource scarcity issue while maintaining high energy density
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 material exhibits excellent structural stability and long-cycle performance, maintaining over 95% capacity retention after 400 cycles, making it suitable for large-scale energy storage devices and applications in renewable energy systems.
Implementation Method 1
The present invention mainly provides charge compensation during charging and discharging based on redox-action of cations and anions (lattice oxygen) of transition metals with electrochemical activity
Data Source
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AI summary
A high-entropy layered oxide material having anion/cation covariance, a preparation method therefor, and a use thereof. The chemical general formula of the high-entropy layered oxide material is Naa[LibMgcNidMneMf]O2+β; wherein M is a transition metal element comprising one or more of the elements Cu, Fe, Zn, Nb, Mo, Ru, Sb, Ta, Bi, Tia, La, and W; a, b, c, d, e, f, and 2+βare respectively the molar ratios occupied by the corresponding elements; the relationships between a, b, c, d, e, f, and 2+β satisfy b+c+d+e+f=1 and a+b+2c+2d+4e+mf=2(2+β), wherein 0.85≤a≤1; 0.05≤b≤0.2; 0.05≤c≤0.2; 0.05≤d≤0.2; 0.2≤e≤0.6; 0.05≤f≤0.2; 0≤β≤0.1, and m is the valence state of M; and a, b, c, d, e, and f satisfy the definition of high entropy, that is, satisfy the formula: S=−R∑i=1Nxilnxi≥1.5R , wherein R is a gas constant, N≥6, xi is any of the values of a, b, c, d, e, and f ; the high-entropy layered oxide material is an O3-phase layered oxide material, the space group is R3m, and the high-entropy layered oxide material is used for a positive electrode active matireal of a sodium ion secondary battery.