High-performance hard carbon anode prepared via an ingenious green-hydrothermal route

Phenolic resin, as a synthetic polymer precursor of hard carbon, has become the core anode precursor of sodiumion batteries (SIBs). However, the carcinogenic formaldehyde is normally adopted in the synthesis of conventional phenolic resins. Meanwhile, the synthetic process is multifarious and prolonged, which is detrimental to mass production. In this paper, an eco-friendly phenolic resin was prepared by an efficient hydrothermal synthesis process using gentle and slightly toxic glyoxylic acid instead of notorious carcinogen formaldehyde. By adjusting the carbonization temperature of as-obtained phenolic precursor, the acquired optimal hard carbon anode material equipped a splendid reversible capacity of 325 mAh g-1 and a high initial coulombic efficiency (ICE) of 88.59%. Besides, it displayed an outstanding rate performance of 161.4 mAh g-1 for 300 cycles at 5 C with the capacity retention rate of 93.31%. When matched against the appropriate cathode, the full battery can provide a high energy density of 239 Wh kg-1, displaying excellent rate capability and cycling stability. The participation of green aldehyde monomer in hydrothermal synthesis process for acquiring phenolic resin is an efficient and scalable approach for obtaining higher energy storage anode, which can pave environmentallyfriendly way for the realization of large-scale energy storage application.

Automated summary

A eco-friendly phenolic resin was prepared by a hydrothermal synthesis process using glyoxylic acid instead of carcinogenic formaldehyde. By adjusting the carbonization temperature, the obtained hard carbon anode material exhibited high reversible capacity and initial coulombic efficiency.