摘要
The off-stoichiometric iron-based phosphate(Na_(3.12)Fe_(2.44)(P_(2)O_(7))_(2),denoted as Na3.12)as a low cost and high structure stability cathode material has been widely studied for sodium-ion batteries(SIBs).However,the lower theoretical specific capacity(117 mAh·g^(-1))has seriously limited its practical application.In this work,we incorporate varying proportion of sodium-iron phosphate(NaFePO_(4))into the Na3.12 to form a series of new high specific capacity mixed-phosphates Na_(3.12+x)Fe_(2.44+x)(P_(2)O_(7))_(2)(PO_(4))x cathode materials for SIBs.After optimizing the introduction amount of NaFePO_(4)into Na_(3.12),the practical reversible of Na_(3.12+x)Fe_(2.44+x)(P_(2)O_(7))_(2)(PO_(4))_(x) increased from 92 to 125.2 mAh·g^(-1).The nano-size Na5.12Fe4.44(P_(2)O_(7))_(2)(PO_(4))_(2) cathode material shows a reversible specific capacity of 125.2 mAh·g^(-1)at 0.1 C in SIBs.Even at 60 C,it still exhibits a reversible specific capacity of 93.3 mAh·g^(-1)and keeps a capacity retention ratio of 87%after 3000 cycles at 20 C.Thereby,we present a novel approach to design a series of off-stoichiometric mixed-phosphates cathode materials for SIBs.
基金
supported by Science and Technology Commission of Shanghai Municipality(No.19D.Z.2271100).
