Tungsten diselenide nanoplates as advanced lithium/sodium ion electrode materials with different storage mechanisms
lithium/sodium ion battery anodes, WSe2 nanoplates, X-ray diffraction, Raman spectroscopy, lithium/sodium storage mechanisms
ABSTRACT Transition-metal dichalcogenides (TMDs) exhibit immense potential as lithium/ sodium-ion electrode materials owing to their sandwich-like layered structures. To optimize their lithium/sodium-storage performance, two issues should be addressed: fundamentally understanding the chemical reaction occurring in TMD electrodes and developing novel TMDs. In this study, WSe2 hexagonal nanoplates were synthesized as lithium/sodium-ion battery (LIB/SIB) electrode materials. For LIBs, the WSe2-nanoplate electrodes achieved a stable reversible capacity and a high rate capability, as well as an ultralong cycle life of up to 1,500 cycles at 1,000 mA·g–1. Most importantly, in situ Raman spectroscopy, ex situ X-ray diffraction (XRD), transmission electron microscopy, and electrochemical impedance spectroscopy measurements performed during the discharge–charge process clearly verified the reversible conversion mechanism, which can be summarized as follows: WSe2 + 4Li+ + 4e– ↔ W + 2Li2Se. The WSe2 nanoplates also exhibited excellent cycling performance and a high rate capability as SIB electrodes. Ex situ XRD and Raman spectroscopy results demonstrate that WSe2 reacted with Na+ more easily and thoroughly than with Li+ and converted to Na2Se and tungsten in the 1st sodiated state. The subsequent charging reaction can be expressed as Na2Se → Se + 2Na+ + 2e–, which differs from the traditional conversion mechanism for LIBs. To our knowledge, this is the first systematic exploration of the lithium/sodium-storage performance of WSe2 and the mechanism involved.
Tsinghua University Press
Wanfeng Yang,Jiawei Wang,Conghui Si,Zhangquan Peng,Zhonghua Zhang, Tungsten diselenide nanoplates as advanced lithium/sodium ion electrode materials with different storage mechanisms. NanoRes.2017, 10(8): 2584–2598