The integration of a battery-type electrode and of a capacitor-type electrode in a single device by proper design is an effective strategy in developing energy storage devices with high energy and power densities. Herein, we present a battery-supercapacitor hybrid device using metallic zinc as anode, a biodegradable ionic liquid (IL) as electrolyte, and graphite as cathode. The recently developed choline acetate ([Ch]OAc) biodegradable IL-based electrolyte enables reversible deposition/stripping of Zn(II). Spongy-like Zn with a high surface area is obtained, which allows fast charge/discharge at high rates. The adsorption/desorption of ions on the surface of the graphite cathode and intercalation/deintercalation of anions into/from the graphite layers occur at the graphite cathode. Raman spectra and X-ray photoelectron reveal the intercalation of IL into and the adsorption of IL on the graphite. Highly reversible adsorption/desorption of ions on the surface of the graphite electrodes in the [Ch]OAc-based electrolyte was demonstrated by a symmetric cell. The Zn/graphite hybrid device delivers an energy density of 53 Wh kg?1 at a power density of ~ 145 W kg?1 and 42 Wh kg?1 at ~ 400 W kg?1. The hybrid device also exhibits a long cycle life with ~ 86% specific capacitance retained after 1000 cycles at a current density of 0.5 A g?1. The combination of well-available zinc, inexpensive graphite, and a biodegradable IL electrolyte in a cell could open new avenues for sustainable energy applications.
A comprehensive study has been conducted to compare the adsorptions of alkali metals (including Li, Na, and K) on the basal plane of graphite by using molecular orbital theory calculations. All three metal atoms prefer to be adsorbed on the "middle hollow site" above a hexagonal aromatic ring. A novel phenomenon was observed, that is, Na, instead of Li or K, is the weakest among the three types of metal atoms in adsorption. The reason is that the SOMO (single occupied molecular orbital) of the Na atom is exactly at the middle point between the HOMO and the LUMO of the graphite layer in energy level. As a result, the SOMO of Na cannot form a stable interaction with either the HOMO or the LUMO of the graphite. On the other hand, the SOMO of Li and K can form a relatively stable interaction with either the HOMO or the LUMO of graphite. Why Li has a relatively stronger adsorption than K on graphite has also been interpreted on the basis of their molecular-orbital energy levels. 相似文献
Dual-ion batteries (DIBs) is a promising technology for large-scale energy storage. However, it is still questionable how material structures affect the anion storage behavior. In this paper, we synthesis graphite with an ultra-large interlayer distance and heteroatomic doping to systematically investigate the combined effects on DIBs. The large interlayer distance of 0.51 nm provides more space for anion storage, while the doping of the heteroatoms reduces the energy barriers for anion intercalation and migration and enhances rapid ionic storage at interfaces simultaneously. Based on the synergistic effects, the DIBs composed of carbon cathode and lithium anode afford ultra-high capacity of 240 mAh g−1 at current density of 100 mA g−1. Dual-carbon batteries (DCBs) using the graphite as both of cathode and anode steadily cycle 2400 times at current density of 1 A g−1. Hence, this work provides a reference to the strategy of material designs of DIBs and DCBs. 相似文献
We modelled the adsorption of benzene, fluorobenzene and meta-di-fluorobenzene on Cu(110) by Density Functional Theory. We found that the adsorption configuration depends on the coverage. At high coverage, benzene assumes a tilted position, while at low coverage a horizontal slightly distorted geometry is favoured. Functionalizing the benzene ring with one or two fluorine atoms weakens the bonding to the surface. A rotation is induced, which decreases the distance of the fluorine atom from the surface. STM simulations reveal that details about both, benzene adsorption geometry and fluorine position, can be only detected at short tip-surface distances. 相似文献