A comparative study of cellulose derived structured carbons on the electrochemical behavior of lithium metal-based batteries

By Kim, Patrick J.; Kim, Kyungho; Pol, Vilas G.
Published in Energy Storage Materials 2019

Abstract

Cellulose nanomaterials with different structures (i.e., cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC)) were carbonized to investigate the effect of morphology and crystallinity of cellulose-derived carbon nanomaterials on the overall electrochemical reactions in Li metal-based batteries. Carbonized CNF (c-CNF) and carbonized CNC (c-CNC) were coated separately on either a Cu current collector or a polypropylene (PP) separator for electrochemical tests. The resulting carbon derived from the amorphous region of CNF contributes to increasing the specific capacity of a cell but decreasing the overall electrical conductivity of the electrode. The c-CNF electrode delivered a relatively high capacity of 412 mAh g?1 at a low current density (0.2 A g?1) in comparison with the c-CNC (370 mAh g?1). In contrast, the c-CNC exhibited better rate capability than the c-CNF. When PP separators modified with c-CNF and c-CNC were employed in Li/Cu cells, it has shown remarkable improvements in Coulombic efficiency and cycle stability (over 120 cycles). This effect is ascribed to the substantially decreased local current density and the improved Li-ion storage in additional c-CNF and c-CNC layers. In addition, Li/LiFePO4 full-cell study tested with modified membranes further demonstrated the beneficial effect of cellulose-derived carbon nanomaterials on electrochemical reactions. Throughout this study, we explored the material characteristics of c-CNF and c-CNC, revealing the strong influence of the resulting carbon originated from the amorphous region of CNF on the electrochemical behaviors in Li ion and Li-metal batteries.

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