Hollow CuO nanoparticles in carbon microspheres prepared from cellulose-cuprammonium solution as anode materials for Li-ion batteries

Biomass derived carbon with hollow metallic structures is considered as eco-friendly and sustainable materials, especially as electrode materials, absorbents and catalysts. Herein, hollow CuO nanoparticles (NPs)@carbon (C) microspheres were fabricated by directly using a cellulose-cuprammonium solution as the starting metallic precursor along with the carbonization and oxidation processes. The hollow CuO NPs were formed spontaneously during the oxidation process following a modified Kirkendall effect. The cellulose derived carbon assisted the formation of the hollow structure and prevented the aggregation of CuO NPs during the thermal treatment. As an integrated material, CuO@C microspheres were used as anodes for lithium-ion batteries. The anodes of CuO@C microspheres exhibited a good cycling stability with a discharge capacity of 630 mA h/g at a rate of 0.1 C (1 C = 1 A/g), which is close to the theoretical specific capacity of the anodes of the pure CuO (670 mA h/g), and a good rate performance with high discharge capacities of 361 mA h/g at a rate of 5 C, which is much higher than that of the bare CuO microspheres (57 mA h/g at 5C). The excellent electrochemical performance could be attributed to the unique carbon combined hollow CuO NPs. This work provided a new pathway for preparing biochar based metallic materials with the inexpensive precursor and high applicable performance.