Isomers of terephthalate derivatives as anodes for sodium-ion batteries

Abstract

Organic electrode materials hold tremendous promise in advancing environmentally friendly and sustainable sodium-ion batteries. However, the reported organic electrodes frequently encounter issues such as low specific capacity, low voltage, and unclear charge storage mechanisms. Exploring the structure–activity relationship of various isomers as battery materials is a key point to develop new promising organic electrode materials. Nevertheless, it has not received much attention in battery research. Herein, we designed and synthesized two isomers based on terephthalic acid derivatives, with the terephthalic acid positioned at the para- and meta-positions of the benzene ring. The resulting Na₄C₂₂H₁₀O₈, sodium [1,1′:4′,1′′-terphenyl]-2,2′′,5,5′′-tetracarboxylate (P-TT) and sodium [1,1′:3′,1′′-terphenyl]-2,2′′,5,5′′-tetracarboxylate (M-TT) are further used as anode materials for sodium-ion batteries, exhibiting initial discharge specific capacities of 205.2 and 193.5 mA h g⁻¹, respectively. After 80 cycles at a current density of 0.5C, P-TT and M-TT respectively demonstrated capacity retention rates of 59.1% and 86.5%. The impact of isomeric variations on their electrochemical performance as electrode materials is also discussed via experimental investigation and simulated calculation, which provide new insight for designing organic electrode materials.