A space-confined strategy towards stable α/β-BiO heterojunction anode for high-energy aqueous battery.

It is very necessary to design a high-capacity and stable BiO anode for nickel-bismuth (Ni//Bi) batteries. In this work, a stable α- and β- phase BiO heterojunction nanocomposite (α/β - BiO) was successfully prepared via a simple "space-confined" strategy and it was used as a superior anode for nickel-bismuth (Ni//Bi) battery. The α/β-BiO obtained by using MCM-41 as a space-confined template possesses a stable structure and enhanced charge transfer capability. Such superior traits vest the designed α/β-BiO electrode with high specific capacity (235 mAh g at 1 A g), extraordinary rate performance (137 mAh g at 40 A g, and ∼58% capacity retention vs 1 A g), and excellent cyclic durability (75% capacity retention after 5000 cycles). Such performances are far superior to that of mono-phase α-BiO and β-BiO electrodes. Furthermore, an excellent Ni//Bi battery with outstanding energy density (∼155 Wh kg) and long cycle life was assembled using the obtained α/β-BiO electrode and a NiCO electrode as anode and cathode, respectively (NiCO//α/β-BiO). This work opens a new alternative strategy for the rational design of efficient electrodes for reliable aqueous rechargeable batteries.