Poly(2,5-Dihydroxyterephthalic Acid) Interlayer Polymer as an Advanced Anode Material for Lithium/Sodium Storage

Abstract

Carbonyl compounds, known for their high theoretical capacity and chemical stability, represent an important class of organic electrode materials (OEMs) that have attracted considerable research interest. Nevertheless, issues such as limited electrical conductivity and remarkable solubility in organic electrolytes have hindered the rate capability and long-term stability of lithium/sodium ion batteries (LIBs/SIBs), thereby constraining their broader utilization. This research focuses on poly(2,5-dihydroxyterephthalic acid) (PDHTA), a polymer synthesized through the condensation polymerization of 2,5-dihydroxyterephthalic acid (DHTA) and formaldehyde. The resultant polymer exhibits an interlayer structure characterized by increased crystallinity and thermal resilience, positioning it as a promising candidate for anode applications in LIBs/SIBs. In LIBs, PDHTA demonstrates a discharge capacity of 180 mAh g−1 after 200 cycles at 50 mA g−1, exceeding the intrinsic capacity of DHTA of 106 mAh g−1. Notably, it maintains a consistent reversible capacity of 68 mAh g−1 even at 480 mA g−1. Furthermore, when used as an anode in SIBs, PDHTA achieves a discharge capacity of 81.5 mAh g−1 after 1000 cycles at 50 mA g−1. Detailed analyses shed light on the Li+ storage mechanism involving the carboxylic carbonyl enolization reaction, which facilitates reversible Li+ intercalation and deintercalation for efficient charge-discharge cycling. This molecular design strategy for OEMs represents a compelling pathway to state-of-the-art sustainable energy storage systems.

Keywords: Polymers, Anode materials, lithium-ion batteries, Sodium-ion batteries, Storage mechanism