Hierarchical porous oviform carbon capsules with double-layer shells derived from mushroom spores for efficient sodium ion storage

Developing carbon materials with well-defined morphologies using renewable feedstocks is highly desirable for electrochemical energy storage application. Herein, we report a new class of hierarchical porous oviform carbon capsules with double-layer shells, which were synthesized via pyrolysis using the mushroom spores of ganoderma lucidum (mainly comprise chitin) and sodium phytate as precursors and activator, respectively. The resultant one-of-a-kind spores derived carbon capsules as anode for sodium ion battery exhibits a high reversible capacity of 311.5 mA h g(-1) at a current density of 0.1 A g(-1) and outstanding cyclic stability at current density of 5 A g(-1), in which the reversible capacity is 125.0 mA h g(-1) and after 5000 charge/discharge cycles, the capacity is 111.1 mA h g(-1) with the retention rate of approximately 88.8%. Furthermore, a full cell constructed using the carbon capsules and Na3V2(PO4)(3) as anode and cathode respectively shows 158.2 mA h g(-1) at 1 A g(-1) and maintains high capacity after 500 cycles, further indicating their excellent performance for sodium storage. This outstanding performance for electrochemical Na+ storage is critically ascribed to the specific morphology with double-layered hierarchical porous hollow structure derive from spores. Meanwhile, this work provides a new designing platform for synthesizing advanced carbon materials for electrochemical storage application using the diversity of mushroom spores in nature.