Improved cycling stability of ferrocene intercalated layered double hydroxides electrodes in aqueous electrolytes

• Ferrocene Intercalated Layered Double Hydroxides (LDH) Electrodes have been successfully synthesized • The electrodes fabricated with the dicarboxylic ferrocene anions intercalated in the LDH matrix have demonstrated a stable capacity of 25 mAh g −1 • This capacity is maintained after more than 100 cycles with 100 % coulombic efficiency • The stabilization of the cycling behavior is achieved in water based 5 to 21m LITFSI electrolytes. Through two redox molecules, mono- and dicarboxylic ferrocene anions (FcMono and FcDi, respectively), interleaved between the lamellae of a layered double hydroxide Mg 2 Al(OH) 6 (LDH), have been synthesized and investigated as electrode materials inwater in salt electrolyte using lithium bis-(trifluoromethanesulfonyl)-imide Li + [N(SO 2 CF 3 ) 2 ] − (LiTFSI) mixed in different amount of H 2 O. The redox activities of the composite electrode materials including Mg 2 Al(OH) 6 [FcMono] 1.0 and Mg 2 Al(OH) 6 [FcDi] 0.5 suffer from the dissolution of the active redox species migrating out of the host structure in water based electrolyte when low molalities are used. However, while increasing the molality of the electrolyte solution Mg 2 Al(OH) 6 [FcDi] 0.5 electrode material performs better than Mg 2 Al(OH) 6 [FcMono] 1.0 ones according to the cycling stability For Mg 2 Al(OH) 6 [FcDi] 0.5 , an optimum behavior is observed for a concentration of LITFSI of at least of 10 m . The electrode exhibits a stable capacity of 25 mAh g −1 which is maintained after more than 100 cycles with 100 % coulombic efficiency. Such stability during cycling is explained by two complementary processes: the preservation of the lamellar structure of Mg 2 Al(OH) 6 [FcDi] 0.5 , FcDi molecule being tethered by its two ends (unlike FcMono tethered at one end only), in connection with the high concentration of the electrolyte in LiTFSI, which helps slowing down the migration of the interleaved redox species out of the structure. This opens the route to re-evaluate LDH-based hybrid materials for water-based energy storage devices. Intercalated Layered Double Hydroxides Electrodes in Aqueous Electrolytes