As a promising alternative to rechargeable LIBs, sodium ion batteries (SIBs) have drawn increasing attention owing to their lower cost; environmentally friendly, excellent recharge ability and higher security. Polyanion compounds including phosphates have been investigated as intriguing cathode materials for SIBs. The open-framework of polyanion compounds is expected to offer facile paths for Na-ion migration, and local environments of polyanions can tailor the operation voltage of a specific redox. Moreover, most of these materials have high thermal stability and oxidative stability at high charging voltage due to the strong covalent bonding of oxygen atom in the polyanionic framework. The performances of Na2-xMxP4O12 where the {M=Ba, La, Gd} have been investigated and the results showed that these new compounds exhibit excellent electrochemical performances. The specific capacitance of NaBaP4O12 as a function of scan rate is plotted in (Fig. 1) values were 172.1F g-1 , 169.36 F g-1 and 161.65 F g-1 at different scan rates. The best performance with high specific energy is 23.89 Wh/kg-1 at a specific power of 1162 Wkg_1 at 0.0002 A cm2 specific current. Thus, even at very high specific current, our synthesized materials shows high specific power without much loss in specific energy. The CV curve of NaBaP4O12 was in a quasi- rectangular shape with a wide potential window (1.5 V) (Fig. 2). The redox potentials from CV and charge/discharge curves it is found that the main migration from/into the crystallographic sites of Na ions is favored to obtain satisfactory properties by a three-step process.

Metal-tetrametaphosphate polyanions: Synthesis, characterization, and electrochemical evaluation for sodium ion battery application

2019 Spring National Meeting

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