Non‐Conjugated Dicarboxylate Anode Materials for Electrochemical Cells

Abstract

Classical organic anode materials for Na‐ion batteries are mostly based on conjugated carboxylate compounds, which can stabilize added electrons by the double‐bond reformation mechanism. Now, 1,4‐cyclohexanedicarboxylic acid (C₈H₁₂O₄, CHDA) with a non‐conjugated ring (−C₆H₁₀−) connected with carboxylates is shown to undergo electrochemical reactions with two Na ions, delivering a high charge specific capacity of 284 mA h g⁻¹ (249 mA h g⁻¹ after 100 cycles), and good rate performance. First‐principles calculations indicate that hydrogen‐transfer‐mediated orbital conversion from antibonding π* to bonding σ stabilize two added electrons, and reactive intermediate with unpaired electron is suppressed by localization of σ‐bonds and steric hindrance. An advantage of CHDA as an anode material is good reversibility and relatively constant voltage. A large variety of organic non‐conjugated compounds are predicted to be promising anode materials for sodium‐ion batteries.