Core-Shell Prussian Blue Analogue for Moisture-Stable Sodium-Ion Cathodes
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Solution Overview
Problem
Prussian blue analog (PBA) materials for sodium-ion secondary batteries suffer from degradation of electrochemical performance during long-term storage due to water absorption, leading to instability and reduced cycling performance.
Innovation Solution
A core-shell structured PBA is developed, where a cladding layer of alkali metal ions such as K, Rb, or Cs is applied to the surface of the PBA core, effectively preventing water entry and enhancing storage stability, while maintaining electrochemical capacity and ion transport efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If PBA material is dehydrated by vacuum heating, then water content is reduced, but the dehydration process is time-consuming and costly
Solution Approach 1:
The patent extracts water molecules from the PBA material through vacuum heating at elevated temperatures (e.g., 100-200°C), removing the harmful substance (water) that causes degradation while preserving the functional PBA structure
Solution Approach 2:
The patent changes physical parameters (temperature and vacuum pressure) to accelerate water removal. By applying vacuum conditions and elevated temperatures simultaneously, the dehydration process achieves thorough water removal in reasonable time without requiring extreme conditions
2Quantity of substance
If PBA material is dehydrated by vacuum heating, then water content is reduced, but manufacturing cost increases
Solution Approach 1:
The patent extracts water molecules from the PBA material through vacuum heating at elevated temperatures (e.g., 100-200°C), removing the harmful substance (water) that causes degradation while preserving the functional PBA structure
Solution Approach 2:
The patent changes physical parameters (temperature and vacuum pressure) to accelerate water removal. By applying vacuum conditions and elevated temperatures simultaneously, the dehydration process achieves thorough water removal in reasonable time without requiring extreme conditions
3Quantity of substance
If dehydrated PBA material is stored in air, then water is removed, but the material easily absorbs water again resulting in rapid degradation
Solution Approach 1:
The patent applies preliminary anti-action by thoroughly dehydrating the PBA material before storage and implementation. By removing water molecules in advance through vacuum heating and maintaining low water content (e.g., ≤0.5 wt%) before battery assembly, the material is prepared in a stable state that resists subsequent water absorption and degradation
Solution Approach 2:
The patent employs inert atmosphere techniques during handling and storage of the dehydrated PBA material. By conducting operations in controlled atmospheres (e.g., argon or nitrogen environments) and using sealed glove boxes, the patent prevents re-absorption of water from air, maintaining the low water content and electrochemical stability of the PBA material
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 core-shell structure significantly improves the long-term storage stability and cycling performance of PBA materials, reducing water absorption and maintaining electrochemical capacity, thus making them suitable for industrial applications in sodium-ion secondary batteries.
Implementation Method 1
the shell can especially effectively hinder the entry of water molecules into the core-shell structure
Implementation Method 2
the dehydration of MnFe-PBA by vacuum drying at 100°C for 30h under a high vacuum of 15mTorr
Implementation Method 3
the relatively large void size of the cube (diameter being of about 4.6Å) and the relatively wide channel (about 4.6Å) in the [100] direction greatly facilitate the rapid migration of alkali metal ions with large ionic radii
Data Source
Figure 1(a)~1(b)
Figure 1(c)~1(d)
Figure 2~3
AI summary
The present application relates to a prussian blue analog having a core-shell structure, which has a core and a cladding layer that clads the core, wherein the chemical formula of the core is the following Formula 1, NaxP[R(CN)6]δ·zH2O Formula 1 wherein the P and R are each independently selected from at least one of transition metal elements, 0<x≤2, 0<δ≤1, and 0≤z≤10, the chemical formula of the cladding layer is the following Formula 2, AyL[M(CN)6]α·wH2O Formula 2 wherein the A is an alkali metal or alkaline earth metal element other than sodium, and the L and M are each independently selected from at least one of transition metal elements, 0<y≤2, 0<α≤1, and 0≤w≤10. The prussian blue analog of the present application has good storage stability, and thus can greatly reduce the manufacturing cost at the subsequent battery cell level. The present application also relates to a method for preparing the prussian blue analog having a core-shell structure, as well as a sodium-ion secondary battery, a battery module, a battery pack and a powered device comprising the same.