Bismuth Based Materials For Highly Durable Lithium And Sodium Storage

Bismuth based materials are uniquely interesting as anode materials in energy storage devices,such as rechargeable batteries,owing to their large volumetric capacity,suitable operating potential and unique alloying ability.The storage of ions in the bismuth based materials contains conversion process and alloying process,and it always results in structure ruin.Therefore,how to avoid this problem and achieve the high capacity durably and robustly remains an open challenge.In this paper,the structure,synthesis and electrochemical performance of bismuth oxide(Bi2O2.33),bismuth sulfide(Bi2S3)and bismuth metal(Bi)were studied.The specific contents are as follows:(1)A composite,composed of reduced graphene oxide(r GO)nanosheets decorated with ultrafine Bi2O2.33 nanodots,was obtained through solvothermal treatment.Because of its high conductivity,large accessible area,and inherent flexibility,this Bi2O2.33/r GO hybrid exhibits stable and robust Li storage(346 m Ah g-1 over 600 cycles at 10 C).As a contrast,the cycling stability of the unanchored Bi2O2.33 without r GO is poor.(2)Similarly,a bio-inspired material of core-shell composite was acquired via solvothermal treatment followed by vapor deposition.And this composite consists of Bi2S3 nanowire assembly intimately encapsulated in polypyrrole(PPy)shell.The Bi2S3 core features a large void space and a short diffusion distance,and benefits the transfer and inset of ions,while the PPy shell is highly conductive,flexible and resilient,allowing for the free volume variation upon ion uptake and release.When used as anode,the Bi2S3-PPy core-shell composite exhibits a superior Li storage cyclability(99% for 500 cycles)and a high rate capability(337 m Ah g-1 at 10 C).This composite also affords a high reversible capacity of 591 m Ah g-1 and a favorable durability for Na storage.The discrepancy between Li and Na storage may correlate to the larger volume change of Bi alloying with Na against with Li.(3)The Al2O3-coated metal Bi composite was directly formed on the Cu foil by electrodeposition and atomic layer deposition(ALD).This product could be used as the electrode without the binder.When the Na PF6-diglyme with better electrode wettability was used as sodium ion battery electrolyte,the Al2O3/Bi/Cu composite shew good performance of electrochemical sodium storage.At 0.5 C rate,the reversible capacity could retain 380 m Ah g-1 after 100 cycles,and the retention rate reached 96.7%.And at 10 C high rate,the reversible capacity can reach 345 m Ah g-1.