Abstract
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 ≈250mAhg-1 at a current density of 25mAg-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.
Highlights
Li-ion batteries (LIBs).[2,3] As the scope materials (OEMs) complement such technologies as they can be sourced from biomass and recycling them is environmentally friendly
The strong peak corresponding to carbonyl ( C O) stretching at 1685 cm–1 present in H2NDCA was noticeably shifted in the spectrum for Na-NDC (MW)
Like the compound obtained using reflux synthesis, Na-NDC (MW) exhibited high thermal stability, with a plateau in the thermogravimetric analysis (TGA) profile up to ≈500 °C, followed by a sharp loss corresponding to the decomposition of the material (Figure S3, Supporting Information)
Summary
The title compound – Na-NDC (MW), was synthesized by heating a mixture of naphthalene-2,6-dicarboxylic acid (H2NDCA) and sodium hydroxide (NaOH) in ethanol using microwave irradiation for 30 min (further details in the Experimental Section). Galvanostatic cycling studies at low current rate (25 mA g–1) showed high first discharge capacities of 318 and 302 mAh g–1 for CMC and sodium alginate-based electrodes, respectively (Figure S16, Supporting Information). Na-NDC (MW) was found to have excellent rate capability when the current rate was increased step wise from 25 to 500 mA g–1, and the cycling capacity was retained when it was lowered back to 25 mA g–1 (Figure 3c) Another aspect in electrode fabrication is to enhance the content of active material and reduce the amount of conductive carbon.[48] In this regard, electrodes were fabricated using CMC as the binder (10%) and different ratios of Na-NDC (MW) and Super C65—70:20 and 80:10. In both these cases the cycling was stable over several cycles
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