Tin modification of sodium manganese hexacyanoferrate as a superior cathode material for sodium ion batteries

Tin modified sodium manganese hexacyanoferrate, as a Prussian blue analogue, is studied as a cathode material for sodium ion batteries. By co precipitation of Sn4 during the synthesis process, the modified sodium manganese hexacyanoferrate materials crystallize with face centered cubic structure with space group Fmm, while the unmodified one possesses a rhombohedral structure with space group Rm. Compared to the unmodified material, the modified materials exhibit smaller particles with rougher surface, showing improved rate capability and cycling stability. The material modified by 10 Sn maintains 80.5 capacity after 100 cycles at 2 C 240 mA g amp; 8722;1 and delivers 53.4 mA h g amp; 8722;1 at 20 C. Both Fe and Mn take part in the redox reaction and the structural changes are reversible upon the initial Na extraction and insertion for both pristine and modified samples. For long term cycling, the modified materials undergo less structural transformation than the pristine material that may lead to a better structural stability, and furthermore to enhanced cycling performanc