Encapsulation of hollow Bi2Se3 particles with conductive polypyrrole for efficient magnesium ion storage

Layered Bi 2 Se 3 has been designed as a promising anode material for aqueous batteries due to its large interlayer spacing and high specific capacity. However, Bi 2 Se 3 is a topological insulator, its interior presents an insulating state, which results in a slow reaction dynamics. Moreover, it is found that unmodified Bi 2 Se 3 has a poor structural stability during charging/discharging. Hence, we design conductive polypyrrole coated hollow Bi 2 Se 3 particles (Bi 2 Se 3 @PPy) to solve these problems. Various experiments show that the PPy possesses bifunctional features and enhance the electrical conductivity and structural stability of Bi 2 Se 3 . The hollow structure of Bi 2 Se 3 exposes abundant active sites and shortens the diffusion paths of Mg 2+ . As a result, at current density of 0.2 A g −1 , Bi 2 Se 3 @PPy offers high discharge capacity of 134 mA h g −1 in aqueous magnesium ion battery. More importantly, Bi 2 Se 3 @PPy//Mn 3 O 4 full cell presents discharge capacity of 66 mA h g −1 at 0.5 A g −1 . Furthermore, Bi 2 Se 3 @PPy exhibits good electrochemical performance in ammonium ion battery. This paper provides a feasible strategy to enhance the structural stability and ionic/electronic conductivity of topological insulator.