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Charge Storage Mechanism and Structural Evolution of Viologen Crystals as the Cathode of Lithium Batteries
Author(s) -
Ma Ting,
Liu Luojia,
Wang Jiaqi,
Lu Yong,
Chen Jun
Publication year - 2020
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202002773
Subject(s) - lithium (medication) , viologen , electrochemistry , electrolyte , iodide , cathode , chemistry , conductivity , inorganic chemistry , ionic conductivity , monoclinic crystal system , electrode , chemical engineering , crystal structure , crystallography , endocrinology , medicine , engineering
Although organic ionic crystals represent an attractive class of active materials for rechargeable batteries owing to their high capacity and low solubility in electrolytes, they generally suffer from limited electronic conductivity and moderate voltage. Furthermore, the charge storage mechanism and structural evolution during the redox processes are still not clearly understood. Here we describe ethyl viologen iodide (EVI 2 ) and ethyl viologen diperchlorate (EV(ClO 4 ) 2 ) as cathode materials of lithium batteries which crystallize in a monoclinic system with alternating organic EV 2+ layers and inorganic I − /ClO 4 − layers. The EVI 2 electrode exhibits a high initial discharge plateau of 3.7 V (vs. Li + /Li) because of its anion storage ability. When I − is replaced by ClO 4 − , the obtained EV(ClO 4 ) 2 electrode displays excellent rate performance with a theoretical capacity of 78 % even at 5 C owing to the good electron conductivity of ClO 4 − layers. EVI 2 and EV(ClO 4 ) 2 also show excellent cycling stability (capacity retention >96 % after 200 cycles).