A general strategy for metal oxide nanoparticles embedded into heterogeneous carbon nanosheets as high-rate lithium-ion battery anodes

Two-dimensional carbon-based composite nanosheets (2D-CCNSs) are expected to be promising electrodes for fast charging lithium-ion batteries. Even though synthesis procedures exist for these materials, current approaches often require rigid reaction conditions and complicated synthetic steps. Herein, we develop a facile and general approach to fabricate a new type of 2D-CCNSs and demonstrate its superiority as a high-rate anode for lithium-ion batteries. It is found that the introduction of a nanocellulose as building unit can guide itself to self-assemble with polydopamine and metal ions to form a 2D inorganic-organic hybrid, which can be directly transformed into 2D-CCNSs after a carbonization treatment without structural deterioration. Unlike common 2D-CCNSs with a pure graphitic or amorphous carbon framework, the as-constructed materials possess a distinctively heterogeneous carbonaceous skeleton comprising graphitic nanorods with a crystalline framework and amorphous carbon with a microporous structure. The synthetic strategy is also demonstrated to be general for embedding numerous metal oxides, such as Fe2O3, CoO, NiO nanoparticles, into the carbon framework just by adjusting the types of metal ions. Profiting from the well-orchestrated structure, the as-prepared 2D-CCNSs exhibit impressive high-rate lithium ion storage performance. For instance, after being fully charged within 40.8 s, a long discharge time as high as 342 min can be achieved accompanied with a high and stable reversible capacity of 560 mA h g-1.