Opportunities in Na/K [Hexacyanoferrate] Frameworks for Sustainable Non-aqueous Na+/K+ batteries

Author(s):  
Ashwani Tyagi ◽  
Nagmani . ◽  
Sreeraj Puravankara

In the past decade, the most sought cathode materials for SIBs and PIBs include transition metal oxides (TMOs), polyanionic phosphates and fluoro phosphates, NASICON-type polyanionic compounds, and alkali metal hexacyanoferrates...

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chenchen Wang ◽  
Luojia Liu ◽  
Shuo Zhao ◽  
Yanchen Liu ◽  
Yubo Yang ◽  
...  

AbstractLayered transition-metal oxides have attracted intensive interest for cathode materials of sodium-ion batteries. However, they are hindered by the limited capacity and inferior phase transition due to the gliding of transition-metal layers upon Na+ extraction and insertion in the cathode materials. Here, we report that the large-sized K+ is riveted in the prismatic Na+ sites of P2-Na0.612K0.056MnO2 to enable more thermodynamically favorable Na+ vacancies. The Mn-O bonds are reinforced to reduce phase transition during charge and discharge. 0.901 Na+ per formula are reversibly extracted and inserted, in which only the two-phase transition of P2 ↔ P’2 occurs at low voltages. It exhibits the highest specific capacity of 240.5 mAh g−1 and energy density of 654 Wh kg−1 based on the redox of Mn3+/Mn4+, and a capacity retention of 98.2% after 100 cycles. This investigation will shed lights on the tuneable chemical environments of transition-metal oxides for advanced cathode materials and promote the development of sodium-ion batteries.


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