Room and elevated temperature lithium-ion storage in structurally submicron carbon spheres with mechanistic

Abstract

Lithium-ion storage in monodisperse submicron carbon spheres (SCS) depends on the inert atmosphere thermal treatment of sonochemically formed polymeric precursors. Battery electrodes of SCS present great initial capacity up to 861 and 1111 A h kg−1 at ambient temperatures 27 and 50 °C, respectively, when cycled at specific current 25 A h kg−1. Beyond initial formation cycles, interestingly, the gravimetric capacity of SCS increases by up to 58% after cycle 50 if cycled up to 3.0 V. Furthermore, capacity change becomes more intense until failure when cycled at 50 °C due to enhanced lithium kinetics. During the first 30 cycles, in situ electrochemical impedance spectroscopy illustrates capacity evolution is coincident with changing capacitive behavior. Subsequently, a model is proposed to relate evolving specific capacity to morphological changes before and during galvanostatic cycling. Further mechanistic support is provided by quantitative characterization of nano-crystallites and phase disorder by X-ray powder diffraction (Scherrer equation) and Raman spectroscopy (peak fitting), elemental composition by organic elemental analysis, and textural properties by isothermal nitrogen sorption. This work provides valuable insight on pertinent ex situ and in situ factors influencing extended voltage applications of synthetic carbons in rechargeable lithium-ion batteries.