Synthesis and Performance Evaluation of Na_(2‐x)Li_xFeP₂O₇ (x=0, 0.6) Hybrid Cathodes

<p></p><div> <p>This study reports hybrid cathodes formation by cation substitution in which Li⁺ substitution has been considered for Na⁺ in the structure of Na_(2-x)Li_xFeP₂O₇ (x=0, 0.6) to form Na_1.4Li_0.6FeP₂O₇ cathodes. Na_(2-x)Li_xFeP₂O₇ (x=0, 0.6) cathodes were synthesized using the solid-state synthesis technique and characterized by various methods. The structural analysis (XRD, FE-SEM) indicates that the submicron-sized, phase pure, and crystalline materials having irregular morphology have been developed. Moreover, Li⁺ substitution does not alter the triclinic parent structure of Na₂FeP₂O₇. Thermogravimetric analysis (TGA) shows that Li⁺ substitution into Na₂FeP₂O₇ improves its thermal stability up to 550 °C with only ∼5 % weight loss. The electrochemical performance of Na₂FeP₂O₇ and Na_1.4Li_0.6FeP₂O₇ in both lithium (Li) and sodium (Na) half-cells is investigated using different electrochemical techniques. It is noticed that Na_1.4Li_0.6FeP₂O₇ is electrochemically active both in lithium (Li) and sodium (Na) cells with promising cyclability. However, compared with Na₂FeP₂O_7, Na_1.4Li_0.6FeP₂O₇ suffers from inferior electrochemical performance, which might be associated with the lattice distortion of Na₂FeP₂O₇ due to Li⁺ substitution having a lower ionic radius than the Na⁺. Considering Na₂FeP₂O₇ as a baseline material, a new hybrid Na_1.4Li_0.6FeP₂O₇ cathode has been developed, which can be used to synthesize other new cathode materials with improved performance.</p> </div><p></p><h2>Other Information</h2> <p> Published in: ChemistrySelect<br> License: <a href="http://creativecommons.org/licenses/by/4.0/" target="_blank">http://creativecommons.org/licenses/by/4.0/</a><br>See article on publisher's website: <a href="http://dx.doi.org/10.1002/slct.202003658" target="_blank">http://dx.doi.org/10.1002/slct.202003658</a></p>