Electrochemical Performances Of Bismuth Sulfide Nanomaterials

Bismuth sulfide(Bi2S3)belong to the main group chalcogenides which have been widely known as a type of semiconductor due to its direct band gap(Eg=1.3 e V). To date, it has applied in sensors, photovoltaic converters, and thermoelectric technology and so on. Also, it has a huge potential in application of hydrogen storage and Li-ion battery owing to its inherent lamellar structure. In this novel, we analyses the relationship between the morphology and performances. Various methods have been chosen to control the morphology and test its electrochemical performances. The contents are as follows:1) 2D disc-like Bi2S3 nanomesh was prepared via hydrothermal method. We adjust the reaction time and temperature to observe its morphology. Finally, we choose the condition of reaction under 180℃ for 3 hours and obtained the robust Bi2S3 nanomesh with 2μm in diameter which was woven by Bi2S3 nanorods measured 40 nm in width and 200 nm in length. After that,in-situ carbon coating treatment have been used to coat the materials with no alternation of its morphology. The 3 nm thick amorphous carbon layer was uniformly coated on the surface of Bi2S3. This effectively restraint its dramatic expansion upon lithiation and delithiation, thus significantly improved the Li-ion storage performances. The capacity can still reach 362 m Ah g-1 after 40 cycles. It also deliver 301 m Ah g-1 even when the current increases to 600 m A g-1 which is superior to other reports.2) Bi2S3-CNT nanocomposite materials were approached via the method of ultrasonic. The Branch-like Bi2S3 tightly anchored on the CNT backbone. Owing to its high conductivity and high ratio of length to diameter, flexible CNT serves as a high pathway for charge. In addition, Bi2S3 particles embrace CNT instead of scattering around which also lowers the contact impedance. The electrochemical test have proved our judgment for its superb cycling and rate performances. It can reach nearly 400 m Ah g-1 under a current of 3 A g-1,and retain 534 m Ah g-1 after 90 cycles.Inspired by Bi2S3-CNT, we control the reaction rate via the ice-bath method and thus Bi2S3@CNT were obtained. The morphology of Bi2S3@CNT is simillar to Bi2S3-CNT while the combination is more compact with a higher thickness and stability. Similar to Bi2S3@CNT, the electrochemical properties were outstanding. It delivers 513 and 457 m Ah g-1 at 0.5 and 1 A g-1 respectively, and the retention rate is above 80%.3) Similar to Bi2S3, Bi2O3 also have a high theoretical capacity. We added Bi(NO3)3.5H2 O solution to the mixture of TAA and CTAB. The Bi3+ immediately forms Bi2O3 nanosheet. As the reaction progresses, the TAA which coated by CTAB was released gradually, and Bi2O3 constantly vulcanized to Bi2S3. The amount of Bi2S3 is tunable via adjustment of time. Bi2O3-Bi2S3 showed initial coulombic efficiency as high as 83.7%, which is superior to other reports(60-70% on average). The heterostructure Bi2O3-Bi2S3 can preserve 433 m Ah g-1 at 600 m A g-1 even after 100 cycles and remain stable. Besides, it still delivers nearly 300 m A g-1 at current of 6 A g-1.