Three-dimensional Carbon-Based Electrodes For Electrochemical Energy Storage

The three-dimensional(3D)interconnected networks can boost superior ion and electron transport kinetics in electrodes to realize high power density of the energy storage devices.Besides,the 3D networks could alleviate the mechanical crack resulting from the volume expansion to improve the electrodes structural stability,which lead to the enhanced calendar life.Carbon materials combine excellent mechanical,electrical properties with very good electrochemical resistance have been promising building blocks for 3D current collectors.However,the fabrication of these electrode structures usually requires complex procedures depending on the specific electrochemically active material that is used.In addition,the structure of carbon materials also has a great effect on the performance of electrodes.In this paper,we prepare and regulate the 3D carbon materials independently and effectively to realize the simultaneously enhanced energy density,power density and cycle stability of the energy storage devices.The main results can be summarized as follows:1.We report the fabrication of a 3D interconnected conductive network with hierarchical porous structures.The CNT-UGF is composed of carbon nanotube forests grown inside the macropores of graphite foam with a density of 12.4 mg cm-3,a specific surface area of 250 m2 g-1,hundreds of micrometer-long channel and 95 wt.%content of sp2-hybridized carbon.The CNT-UGF can be loaded with element S and Li metal as cathode and anode,respectively.A battery assembled with the S/CNT-UGF cathode and Li/CNT-UGF anode delivered a gravimetric capacity of 860 mA h g-1 at 12 C and can retain 80%of the initial capacity after 400 cycles at 1 C.2.We prepare a scaffold made of covalently-connected graphite microtubes(CT-scaffold)by a self-assembly of Ni microwires as the template to modify the pore size of the 3D carbon network.The as-prepared scaffold consists of graphite microtubes with a pore size of tens of micrometers and StA of 12 m2 g-1.The moderate surface area of the GT-scaffold was suggested to be responsible for the limited Li consumption and dendrite growth,thus the Li/GT-scaffold anode can be cycled at a current density of 10 mA cm-2 to deliver a reversible areal capacity of 10 mA h cm-2 with Li utilization of 91%,and lifespan of up to 3000 h.3.We fabricate a stable lithium-scaffold composite electrode by infusing molten lithium-based alloy into a 3D carbon fiber with“lithiophilic" coating.The preexisting scaffold serves as a rigid host with Li uniformly confined inside to accommodate the electrode-level virtually infinite volume change of Li metal during cycling.The porous electrode reduces the effective current density,thus,flat voltage profiles and stable cycling of more than 1000 hours is achieved even at a high reversible areal capacity of 12 mA h cm-2...