Heteroatom Doped-Carbon Nanospheres for Energy Storage Systems

Abstract

Graphite-based lithium batteries hold a significant position in the market since graphite is the only material to combine low cost, performance and easy processability, three factors which are crucial for industrial production and realization in true applications. Much effort is now being expended in attempts to advancing anode materials (silicon, transition metal oxides, various alloys etc.) for Li-ion batteries driven by the ongoing development of high power demanding applications and tools [1]. Novel materials have larger theoretical capacity than graphite (372 mAh g -1 ) but often suffer from low electrical conductivity and large volume expansion which lead to poor cycling performance. Also, new promising technologies are emerging like Na-ion batteries that can be key as an alternative energy storage system [2] and require the exploration of different carbonaceous materials. Here we investigate the performance of a novel type of heteroatom co-doped (nitrogen, phosphorous and sulfur) carbon nanospheres (CNSs) with high specific surface area as anode materials for lithium and sodium ion batteries. The one-step synthesis of highly cross-linked hybrid organo(cyclotriphosphazenes) (OPZs) is an excellent and high efficient method to prepare various nanostructured materials like nanospheres, nanotubes, core-shell and hollow particles. The CNSs were obtained from carbonization of OPZs with 300 nm in diameter. Irreversible capacity loss due solid-electrolyte interface (SEI) layer formation is a common issue for carbonaceous materials used in electrodes for Lithium cells and studying the correlation of the capacity loss with multiple atom doping is essential. Work to be discussed here will present results of the investigation of the effect of the carbonization temperature on the microstructural and elemental composition and ultimately the electrochemical behaviour of the CNSs. The as prepared CNSs showed remarkable cycling stability for more than 1000 cycles delivering a capacity of about 130 mAhg -1 at a current rate of 1C. In addition a significant coulombic efficiency as high as 99.99% was maintained during the long cycling thereby showing great promise for application in Lithium batteries. The high specific surface area, porous structure and multi-heteroatom doping all contributed to the electrochemical performance of the CNSs. Heteroatom doped CNSs are potential materials for a set of different important applications in catalysis, supercapacitors and hydrogen storage and synergistic effects of dopant atoms could be key for advancing technology. [1] N. Nitta, F. Wu, J. T. Lee, G. Yushin, Mater. Today, 18 (2015) 252 [2] B. L. Ellis, L. F. Nazar, Curr. Opin. Solid State Mater. Sci. 16 (2012) 168