Controlled synthesis of macroscopic three-dimensional hollow reticulate hard carbon as long-life anode materials for Na-ion batteries

The controlled conversion of biomass is necessary for their efficient utilization. In this work, we report the controlled synthesis of a novel macroscopic three-dimensional hollow reticulate hard carbon by hydrothermal pretreatment and further low temperature (600 °C) pyrolysis method. The carbonization mechanism is presented based on differential thermal analysis, which shows that the hydrothermal pretreatment gets through the reticulate structure by removing flavonoids and the pyrolysis temperature is a key factor for inheriting the unique architecture. Tested against sodium, the hard carbon exhibits good cycling stability, showing capacity retention of 90% after 1000 cycles. The excellent Na-ion storage property is attributed to the interconnected three-dimensional architecture, the abundant O-containing functional groups and the large interlayer spacing.