Binder less-integrated freestanding carbon film derived from pitch as light weight and high-power anode for sodium-ion battery

To realize the large scale application of sodium-ion batteries (SIBs), a stable, cost-effective anode is desired. Pitch is a potential low-cost precursor to synthesize soft carbon anode for SIBs. However, it exhibits poor Na-ion storage. Herein, we report the facile synthesis of pitch derived-binder less-metal free-freestanding anode for storing Na-ions by one-step pyrolysis process between the temperature range 700-1000 degrees C under nitrogen atmosphere. We replace conventional Cu-current collectors with non-graphitic carbon fiber (CFs) mats. The electrode architecture not only eliminates the metallic current collector, conductive diluents, and inactive organic binder but also provides an ideal porous network for sodium-ion and electrolyte diffusion into the bulk of the electrode. The freestanding electrode delivers a reversible capacity of 310 mAh g(-1) in comparison to 180 mAh g(-1) for the conventional electrode at the current density of 50 mA g(-1). Good C rate performance and cycling stability over 500 cycles (at 1 A g(-1)) of this freestanding electrode indicate as a promising anode for SIBs. The evolution of plateau region capacity (<0.1 V) in free-standing electrodes leads to higher capacity value in comparison to a conventional electrode. To understand further, the cyclic voltammetry curves at various sweep rates are used and it is observed that the Na-ion storage behavior within the conventional electrode is mostly capacitive, whereas the behavior is diffusion dominant in case of the freestanding electrode. Finally, the freestanding electrodes are implemented as anodes and fluorophosphate based material as the cathode to realize its practical realization in sodium-ion full cell. (c) 2020 Elsevier Ltd. All rights reserved.