Rapid preparation of binary mixtures of sodium carboxylates as anodes in sodium-ion batteries.

Sodium-ion batteries are emerging as a sustainable solution to tackle the growing global energy demands. In this context, organic electrode materials complement such technologies as they are composed of earth-abundant elements. As organic anodes, sodium carboxylates exhibit promising applicability in a wide range of molecules. To harness the advantages of individual systems and to minimise their limitations, in this work, an approach to form binary mixtures of sodium carboxylates using one-pot, microwave-assisted synthesis is presented. The target mixtures were synthesised in 30 min with disodium naphthalene-2,6-dicarboxylate (Na-NDC) as a common constituent in all. Both components in all mixtures were shown to participate in the charge storage and had a considerable effect on the performance characteristics, such as specific capacity and working voltage, in half and full cell formats. This approach opens a new avenue for enabling organic materials to be considered as more competitive candidates in sodium-ion batteries and promote their use in other material classes to overcome their limitations.

Rapid Microwave-Assisted Synthesis and Electrode Optimization of Organic Anode Materials in Sodium-Ion Batteries.

Sodium-ion batteries are commanding increasing attention owing to their promising electrochemical performance and sustainability. Organic electrode materials (OEMs) complement such technologies as they can be sourced from biomass and recycling them is environmentally friendly. Organic anodes based on sodium carboxylates have exhibited immense potential, except the limitation of current synthesis methods concerning upscaling and energy costs. In this work, a rapid and energy efficient microwave-assisted synthesis for organic anodes is presented using sodium naphthalene-2,6-dicarboxylate as a model compound. Optimizing the synthesis and electrode composition enables the compound to deliver a reversible initial capacity of ≈250 mAh g-1 at a current density of 25 mA g-1 with a high initial Coulombic efficiency (≈78%). The capacity is stable over 400 cycles and the compound also exhibits good rate performance. The successful demonstration of this rapid synthesis may facilitate the transition to preparing organic battery materials by scalable, efficient methods.

Sodium Naphthalene-2,6-dicarboxylate: An Anode for Sodium Batteries.

The conjugated dicarboxylate sodium naphthalene-2,6-dicarboxylate (Na2 NDC) was prepared by a low-energy-consumption reflux method, and its performance as a negative electrode for sodium-ion batteries was evaluated in electrochemical cells. The structure of Na2 NDC was solved for the first time (monoclinic P21 /c) from powder XRD data and consists of π-stacked naphthalene units separated by sodium-oxygen layers. Through an appropriate choice of binder and conducting carbon additive, Na2 NDC exhibited a reversible two electron sodium insertion at approximately 0.4 V (vs. Na+ /Na) with remarkably stable capacities of approximately 200 mAh g-1 at a rate of C/2 and good rate capability (≈133 mAh g-1 at 5 C). In parallel, the high thermal stability of the material was demonstrated by high-temperature XRD: the framework remained intact to above 500 °C.