Layered Oxide Cathode Composition for Oxygen-Stable Sodium-Ion Cycling
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Solution Overview
Problem
Lithium-ion batteries face limitations due to scarce lithium resources, and sodium-ion batteries, despite having cost and supply advantages, suffer from inferior performance and stability issues, particularly with O3-type layered transition metal oxides experiencing unstable oxygen holes under high voltage, leading to reduced specific capacity and coulombic efficiency.
Innovation Solution
A layered oxide with the formula NaxMnyAaQbCcO2, where A is Fe and Ni, Q is transition metals like Cu, Zn, or Ti, and C is Al or B, is developed, with specific valence and ionic potential ratios to stabilize oxygen holes and inhibit irreversible losses, enhancing structural stability and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the charging voltage is increased to 4.0 V or above to improve capacity, then more active sodium can be provided, but oxygen in the layered oxide loses electrons forming unstable holes, causing structure damage and oxygen losses
Solution Approach 1:
The patent modifies the chemical composition parameters of the layered oxide by introducing multiple dopant elements (A, Q, C) with specific valence states and ionic potentials. This changes the electronic structure and stabilizes oxygen holes formed at high voltage, allowing the material to maintain structural integrity during deep charge-discharge cycles while providing increased capacity.
Solution Approach 2:
The patent creates a composite doped layered oxide structure combining multiple elements (transition metals A, Q with main group elements C) in a unified crystal lattice. This composite approach synergistically stabilizes the structure against oxygen loss and structural collapse while maintaining high sodium content and electrochemical activity.
2Use of energy by moving object
If high voltage charging is applied to increase capacity, then energy density improves, but specific capacity and coulombic efficiency reduce due to oxygen losses and structure damage
Solution Approach 1:
The patent optimizes the valence state parameters of dopant elements (A with +3/+4, Q with +2/+3, C with +3) to create a balanced electronic structure. This parameter optimization allows the material to achieve high energy density through deep charging while maintaining high specific capacity by preventing oxygen loss and structural degradation.
3Quantity of substance
If sodium content is increased to improve capacity, then more active sodium is available, but structural stability decreases leading to poor cycle performance
Solution Approach 1:
The patent designs a composite doped structure where multiple elements (A, Q, C) work synergistically to stabilize the layered oxide structure. The combination of transition metals with different valences and main group elements creates a robust framework that can accommodate high sodium content while maintaining structural integrity through deep charge-discharge cycles.
Solution Approach 2:
The patent introduces dopant elements at specific positions within the layered oxide structure to locally reinforce the crystal lattice. The dopants A, Q, and C are distributed throughout the structure to provide localized stabilization centers that prevent structural collapse while allowing high overall sodium content.
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 solution improves the specific capacity and coulombic efficiency of sodium-ion batteries by stabilizing oxygen holes and preventing structural collapse, resulting in better cycle performance and energy density.
Implementation Method 1
a d orbital of the Q element and a 2p orbital of oxygen in the oxide are hybridized to form a hybrid orbital, and a local hole in oxygen may be stabilized by the hybrid orbital
Implementation Method 2
the C element in an ionic state has a high ionic potential and highly interacts with oxygen, its bonding with oxygen has a high covalent bond component
Implementation Method 3
its bonding with oxygen has a high covalent bond component
Implementation Method 4
oxygen in the layered oxide loses electrons at the high voltage, resulting in the formation of a hole
Data Source
AI summary
Provided are a layered oxide and a preparation method thereof, a positive electrode sheet, a secondary battery, a battery module, a battery pack and an electrical apparatus. The layered oxide includes an oxide with the general formula NaxMnyAaQbCcO2, where A is one or two of Fe and Ni; Q is one or more of transition metal elements containing 3d or 4d orbital electrons except Fe and Ni; C is one or two of Al and B, 0.66<x≤1, 0.2≤y≤0.6, 0.3≤a≤0.6, 0<b≤0.2, 0<c≤0.1, and 1≤b/c≤100. The A element undergoes valence changes to provide charge compensation in a charge and discharge process, thereby improving the specific capacity of the layered oxide; the Q element and oxygen form a hybrid orbital, inhibiting irreversible oxygen losses and structure collapse of oxygen under a high voltage; the C element has a high ionic potential so as to effectively inhibit oxygen losses; and 1≤b/c≤100.