Perchlorate ion doped polypyrrole coated ZnS sphere composites as a sodium-ion battery anode with superior rate capability enhanced by pseudocapacitance

Abstract

Considering the inferior rate capability of conversion-type transition-metal sulphides (TMSs) caused by severe volume expansion and poor electronic conductivity, a composite of perchlorate ion (ClO₄⁻) doped polypyrrole (PPy) coated ZnS spheres (denoted as ZnS@d-PPy) has been synthesized via a soft chemistry method. Benefiting from the improved conductivity, the protection of the PPy coating and ClO₄⁻ doping, ZnS@d-PPy exhibits decent cycling performance (419 mA h g⁻¹ after 30 cycles at 100 mA g⁻¹) and superior rate capability (203 mA h g⁻¹ at 4 A g⁻¹), which is enhanced by pseudocapacitance when being applied in sodium-ion batteries (SIBs).