Abstract
3D electrode design is normally opted for multiple advantages, however, instability/detachment of active material causes the pulverization and degradation of the structure, and ultimately poor cyclic stability. Here, a dually protected, highly compressible, and freestanding anode is presented for sodium‐ion batteries, where 3D carbon nanotube (CNT) sponge is decorated with homogeneously dispersed CoSe2 nanoparticles (NPs) which are protected under carbon overcoat (CNT/CoSe2/C). The 3D CNT sponge delivers enough space for high mass loading while providing high mechanical strength and faster conduction pathway among the NPs. The outer amorphous carbon overcoat controls the formation of solid electrolyte interphase film by avoiding direct contact of CoSe2 with electrolyte, accommodates large volume changes, and ultimately enhances the overall conductivity of cell and assists in transmitting electron to an external circuit. Moreover, the hybrid can be densified up to 11‐fold without affecting its microstructure that results in ultrahigh areal mass loading of 17.4 mg cm−2 and an areal capacity of 7.03 mAh cm−2 along with a high gravimetric capacity of 531 mAh g−1 at 100 mA g−1. Thus, compact and smart devices can be realized by this new electrode design for heavy‐duty commercial applications.
Highlights
carbon nanotube (CNT) sponge delivers enough space for high mass loading while providing resistance resulted in capacity fading high mechanical strength and faster conduction pathway among the NPs
The outer amorphous carbon overcoat controls the formation of solid electrolyte interphase film by avoiding direct contact of CoSe2 with electrolyte, accommodates large volume changes, and enhances the overall and hindered the practical application of transition metal diselenides.[9,11]
Among various 3D conductive scaffolds, 3D carbon nanotube (CNT) sponges have found a lot of attention lately due to their ultrahigh porosity, conductivity, and well-interconnected 3D networks that provide high mass flow and allow high mass loading in minimal area.[23,24,25,26]
Summary
The areal mass loading (Ma) or density (d) of as-obtained electrode was determined by Ma = dV/A = dh, where d, V, A, and h are the density, volume, base area, and thickness of the hybrid sponge, respectively. CNT/CoSe2 and CNT/CoSe2/C showed initial discharge and charge capacities (normalized to active mass of the electrodes) of 857 and 535, 952, and 544 mAh g−1, respectively.
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