Lignin‐Derived Hard Carbon Microspheres Synthesized via Emulsion‐Solvent Evaporation as Anode for Sodium Storage

Lignin‐derived hard carbon microspheres with different amphiphilic carbonaceous material (ACM) contents are synthesized through a facile emulsion‐solvent evaporation process and subsequent thermal treatment. The influence of lignin/ACM mass ratio on morphology, microstructure, thermal stability, and electrochemical properties of carbon microspheres is studied in detail. Combined with Fourier‐transform infrared spectroscopy (FT‐IR) and thermogravimetric analysis, the interaction between lignin and ACM leads to enhanced thermal stability with a carbonization yield of 50.6%. Meanwhile, X‐ray diffraction (XRD) results indicate enlarged graphite‐like crystallite dimensions, L a and L c ,which contribute to electric conductivity. Due to ACM addition, the electrochemical performance is improved. When the mass ratio of lignin/ACM is 3:1, the sample exhibits a well‐balanced performance. The reversible capacity is 296.5 mAh g −1 with a high initial Coulombic efficiency of 82.0%. In the cycling test, the sample retains a capacity of 276.8 mAh g −1 after 100 cycles, corresponding to a capacity retention ratio of 90.8%.