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A layered double hydroxide (LDH) compound LDH ([Mg 2 Al(OH) 6 ] ⁺ x 2 H 2 O) intercalated with a redox active organic anion, Anthraquinone-2-sulfonate (AQS), has been envisioned as an electrode material for high power aqueous based battery. The purpose is to use this interlayer redox active molecule for enhancement of the specific capacity at the L...
Citations
... [34,79,80] In more recent work, we showed that redox active anions like anthraquinone sulfonate, riboflavin phosphate or ferrocene carboxylate intercalated in LDH layers, display a redox activity that can be used in electrochemical energy storage application using an aqueous electrolyte. [81,82] By involving both the cationic layers as well as the interlayer space of the LDH electrode materials for energy storage, this approach can lead to further enhancement of the specific capacity of LDH based electrodes. However, in all of these studies very limited cycling stability has been depicted. ...
... In the case of anthraquinone sulfonate intercalated in a Mg 2 Al(OH) 6 LDH, dissolution of the intercalated redox active anthraquinone anions into the aqueous electrolyte was observed which resulted in a rapid loss of specific capacity during cycling. [82] There, the dissolution was described as intrinsic since the charge imbalance in the LDH structure after reduction forces the anions to leave the electrode. ...
... This objective is approached in two ways. First we tried to clarify the influence of the valence of the intercalated redox active organic anions on the release of the active anions from the electrode as previously reported [81,82] and therewith the cycling stability of the active material. Then the possible influence of the electrolyte media on the release phenomenon and subsequently on the cycling stability was investigated. ...
In this work, the layered double hydroxide (LDH) Mg2Al(OH)6 was intercalated with redox active ferrocene carboxylate anions in order to implement charge storage capability to the interlayer spaces of the LDH structure. Two sets of anions, namely mono‐ and dicarboxylic ferrocene, were intercalated to produce two different active materials: MgAl‐FcMono and MgAl‐FcDi. The electrochemical investigation of these two materials was performed in two model electrolytes: 1 M LiTFSI in H2O and Pyr13TFSI. In the aqueous electrolyte, the first charge reaches the full theoretic capacity of ca. 60 and 40 mAh g⁻¹ for both materials. However, significantly less capacity is stored and delivered during subsequent cycles. In‐situ UV/vis experiments identified the loss as a release of charged ferrocene anions from the LDH during oxidation in the charging process, which is more severe for MgAl‐FcMono. It is possible to prevent this release of redox species by the use of the ionic liquid Pyr13TFSI as a high concentrated electrolyte. Subsequently, both materials cycled very steadily with high coulombic efficiency for 150 cycles. This better understanding of the capacity degradation of the LDH‐ferrocene active material is key to improving this new and promising concept of using modified LDHs as active material in energy storage application.
