Facile Synthesis of N,P‐codoped Hard Carbon Nanoporous Microspheres from Lignin for High‐Performance Anodes of Sodium‐Ion Batteries

Abstract We demonstrate a facile emulsion‐solvent evaporation process to easily convert lignin into nanoporous N,P‐codoped hard carbon microspheres. The combined physiochemical characterizations indicate this material possesses micro‐structure suitable for electrochemical energy storage. The electrochemical measurements of sodium ion battery (SIB) show that such lignin‐derived carbon microspheres also follow the widely‐accepted adsorption‐intercalation Na‐storage mechanism. The Na + diffusion coefficient in as‐obtained electrode could reach 10 −9 cm 2 s −1 . They exhibit quite excellent and balanced Na‐storage performances, such as large reversible and low‐voltage capacity (up to 307–336 and 229–246 mAh g −1 , respectively), high initial coulombic efficiency (78.7–82.4 %), and good rate performance as well as long cycling stability (e. g., retaining at 248 mAh g −1 and a retention of ∼92.2 % after running at 0.1 A g −1 for 200 cycles). Consequently, this work not only provides a facile approach to realize high added‐value utilization of lignin but also contributes to the development of eco‐environmental batteries using low‐cost materials.