1. Unusual Na+ Ion Intercalation/Deintercalation in Metal-Rich Cu1.8S for Na-Ion Batteries
- Author
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Donghyeok Shin, Taeseup Song, Jiseok Kwon, Hyunjung Park, Heechae Choi, Xiong Wen David Lou, and School of Chemical and Biomedical Engineering
- Subjects
Reaction mechanism ,Materials science ,Sodium ,Intercalation (chemistry) ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,engineering.material ,010402 general chemistry ,Digenite ,Electrochemistry ,01 natural sciences ,Metal ,Oxidation state ,General Materials Science ,Chemical engineering [Engineering] ,General Engineering ,Metal Sulfide ,021001 nanoscience & nanotechnology ,Digenite Cu1.8S ,Copper ,0104 chemical sciences ,Crystallography ,chemistry ,visual_art ,engineering ,visual_art.visual_art_medium ,0210 nano-technology - Abstract
A key issue with Na-ion batteries is the development of active materials with stable electrochemical reversibility through the understanding of their sodium storage mechanisms. We report a sodium storage mechanism and properties of a new anode material, digenite Cu1.8S, based on its crystallographic study. It is revealed that copper sulfides (CuxS) can have metal-rich formulas (x ≥ 1.6), due to the unique oxidation state of +1 found in group 11 elements. These phases enable the unit cell to consist of all strong Cu–S bonds and no direct S–S bonds, which are vulnerable to external stress/strain that could result in bond cleavage as well as decomposition. Because of its structural rigidness, the Cu1.8S shows an intercalation/deintercalation reaction mechanism even in a low potential window of 0.1–2.2 V versus Na/Na+ without irreversible phase transformation, which most of the metal sulfides experience through a conversion reaction mechanism. It uptakes, on average, 1.4 Na+ ions per unit cell (∼250 mAh g–1) and exhibits ∼100% retention over 1000 cycles at 2C in a tuned voltage range of 0.5–2.2 V through an overall solid solution reaction with negligible phase separation.
- Published
- 2018