Layered transition metal compounds represent a major playground to explore unconventional electric or magnetic properties. In that framework, topochemical approaches that mostly preserve the topology of layered reactants have been intensively investigated to tune properties and/or design new materials. Topochemical reactions often involve the insertion or deinsertion of a chemical element accompanied by a change of oxidation state of the cations only. Conversely, cases where anions play the role of redox centers are very scarce. Here we show that the insertion of copper into two dimensional precursors containing chalcogen dimers (Q ) (Q=S, Se) can produce layered materials with extended (CuQ) sheets. The reality of this topochemical reaction is demonstrated here for different pristine materials, namely La O S , Ba F S , and LaSe . Therefore, this work opens up a new synthetic strategy to design layered transition metal compounds from precursors containing polyanionic redox centers.

Thick electrodes with sodium and even anions intercalation organic compounds integrated in a neutral-pH aqueous battery offer unique advantages in terms of round trip efficiency, environmental impact, and scalability for off or in-grid renewable energy storage. Herein we report on the first anion-rocking chair / dual-ion organic battery. The latter reaches 35 Wh/kgmaterials at C/8 rate. It shows remarkable cyclability and Coulombic efficiency in a cheap and neutral NaClO4 electrolyte pouch cell with highly loaded millimeter thick electrodes (5 mAh/cm²). This achievement is based on a thorough study of a commercial benzene TEMPO compound (4-hydroxy TEMPO benzoate) and its naphthalene derivative (4-carboxy TEMPO naphthalate) as cathode materials, and a bipyridinium-naphthalene oligomer as the anode. Combined UV-vis spectroelectrochemistry and operando XRD account for the much improved cyclability of the hydrophobic 4-carboxy TEMPO naphthalate at the expense of a lower specific capacity. This trend is reversed in the case of the 4-hydroxy TEMPO benzoate derivative. Results show kinetic limitations of the 4-hydroxy TEMPO benzoate are associated with the surrounding composite electrode, while inner-grain ionic and/or electronic transports play a decisive role for the 4-carboxy TEMPO naphthalate.