Layered Iron Oxide Anode for Stable Sodium-Ion Intercalation
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Solution Overview
Problem
Sodium secondary batteries face challenges due to the slow diffusion rate and low reaction activity of sodium ions, limiting the materials that can be used for anode active materials, and existing materials from lithium secondary batteries often result in poor performance or rapid capacity degradation when applied to sodium batteries.
Innovation Solution
An anode active material with a layered crystal structure formed from iron oxide nanoplatelets and organic anions, specifically acetate-based compounds, is developed to enhance the intercalation and deintercalation of sodium ions, featuring a lepidocrocite-type structure with expanded lattice constants and a biotic-reaction-type conversion mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional anode materials from lithium secondary batteries are applied to sodium secondary batteries, then the battery structure is established, but capacity degradation occurs rapidly and electrochemical properties deteriorate
Solution Approach 1:
The patent changes the crystal structure parameters of the anode material by controlling the oxidation state of iron (Fe2+ and Fe3+ mixture) and adjusting the lattice spacing to accommodate larger sodium ions, thereby improving cycle stability and capacity retention in sodium secondary batteries
Solution Approach 2:
The patent uses composite iron oxide materials with mixed valence states (Fe2+ and Fe3+) and combines them with conductive agents and binders to create an anode material that maintains both electrochemical activity and structural stability during sodium ion intercalation and deintercalation cycles
2Adaptability or versatility
If sodium ions are used in the battery, then the battery can operate with alternative materials to lithium, but the diffusion rate of sodium ions is slow and reaction activity is low
Solution Approach 1:
The patent creates local regions with different iron oxidation states (Fe2+ and Fe3+) within the anode material structure, where Fe2+ regions facilitate faster sodium ion diffusion while Fe3+ regions provide stable reaction sites, thereby improving both ion diffusion rate and reaction activity
Solution Approach 2:
The patent utilizes the mixed valence state dimension of iron oxide materials to enhance electrochemical performance, where the coexistence of Fe2+ and Fe3+ creates additional charge transfer pathways and improves sodium ion diffusion kinetics beyond what single-valence materials can achieve
3Reliability
If iron oxide materials are used to control oxidation number change, then electrochemical properties are improved, but the crystal structure must be precisely controlled to maintain stability
Solution Approach 1:
The patent performs preliminary synthesis of iron oxide particles with controlled size (1-10 μm) and specific surface area (5-50 m²/g) before assembling them into electrodes, ensuring that the electrochemical activity and structural stability are optimized in advance, thereby reducing the need for complex in-situ structural control during battery operation
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
This solution improves the electrochemical properties and cycle stability of sodium secondary batteries by facilitating the intercalation of sodium ions and maintaining structural stability, achieving high reversible capacity and retention capacity over multiple cycles.
Implementation Method 1
an anode active material capable of reversibly intercalating and deintercalating sodium ions
Implementation Method 2
control the rapid oxidation number change of iron ions occurring during the oxidation-reduction conversion reaction process
Data Source
AI summary
The present disclosure relates to an anode active material for a sodium secondary battery, which has a layered crystal structure and is formed of nanoplatelets containing iron oxide having organic anions, and in which the nanoplatelets are provided in plural numbers and formed in a stacking structure spaced apart at a first interval.