A Dual‐graphite Battery with Pure 1‐Butyl‐1‐methylpyrrolidinium bis(trifluoromethylsulfonyl) Imide as the Electrolyte

Abstract

Rechargeable dual‐ion batteries are considered to be potential candidates for applications in electrochemical energy storage devices. Ionic liquid is one of the most promising electrolytes due to its superior ionic conductivity and the wide electrochemical window. In this work, a novel dual‐graphite battery system was developed based on a pure 1‐butyl‐1‐methylpyrrolidinium bis(trifluoromethylsulfonyl) imide ionic liquid electrolyte and dual graphite electrodes. The working mechanism of the dual‐graphite battery based on a pure ionic liquid electrolyte without any metallic elements was proposed and investigated in detail. The cell delivers a reversible specific capacity of 49 mAh g−1 at a current density of 50 mA g−1, a high Coulombic efficiency of approximately 97.4 % and a fine cycling stability at high cut‐off voltage 4.6 V over 100 cycles. Moreover, the dual‐ion battery system, which is made entirely of non‐metallic elements, exhibits a high and obvious discharge voltage plateaus at about 3.7 V. These results encourage the further development of new types of futuristic rechargeable non‐metallic battery energy storage systems.

Electrolytes for Dual‐Carbon Batteries

“…Recently, Wang et al. established a dual‐graphite battery based on a pure Pyr 14 TFSI electrolyte (Figure a), which could deliver a reversible capacity of 49 mAh g −1 (based on cathode mass) at 50 mA g −1 in the voltage range of 1.0–4.6 V. The battery displayed a decent cycling stability with a capacity retention of 60 % after 100 cycles and an average CE of 97.4 % (Figure b) . The capacity fading may be ascribed to the inferior compatibility of Pyr 14 + with the graphite anode, which is consistent with the Pyr 14 TFSI‐based electrolyte (Section 2.2.1).…”

Developing Dual‐Graphite Batteries with Pure 1‐Ethyl‐3‐methylimidazolium Trifluoromethanesulfonate Ionic Liquid as the Electrolyte

“…The corresponding coulombic efficiency (C eff ) is 52.1 % at a current rate of 4 C (1 C corresponding to 100 mA g −1 , the same below) over a voltage range of 1.0‐3.9 V. Interestingly, in Figure b, when the cathode graphite was in excess, the discharge capacity can reach up to 46.2 mAh g −1 (based on the mass of graphite at the anode) and two discharge voltage plateaus at approximately 3.3 and 2.2 V are observed. This phenomenon can be due to the different stages of EMIm + cation intercalation into graphite . As the cycle number increases, the 2.2 V discharge plateau degenerates, and almost disappears in the 7 th cycle, indicating that some side reactions occur, such as the irreversible de‐intercalation of the EMIm + cation and the irreversible destruction of the graphite structures.…”

“…To obtain a deeper understanding of the intercalation/de‐intercalation processes of the two ions into/from NG or KS6 graphite, ex‐situ X‐ray diffraction and ex‐situ Raman spectra tests were conducted on the graphite electrodes at different states in the second cycle (current rate: 2 C). Herein, to ensure that the graphite intercalation of the two ions were tested at the same conditions, the mass ratio of cathode and anode graphite was set as 1 : 1.…”

“…Fan et al [11] reported a dual-ion battery with a pure PP 14 TFSI ionic liquid electrolyte possessing a high discharge plateau initiated at 4.4 V and superior cycling stability. Wang et al [12] developed a dualgraphite battery employing a pure 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide (Pyr 14 TFSI) electrolyte, which presented a well-defined discharge plateau at approximately 3.7 V. Lv et al [13] reported a pure [DMPI][AlCl 4 ] ionic liquid-based dual-ion battery with a superior chargedischarge plateau and long cycling stability. Additionally, DIBs based on EMImAlCl 4 , [14] PP 14 TFSI, [15] and Pyr 14 TFSI [7d,16] ionic liquids have also been studied.…”

A Dual‐Ion Battery with a Ferric Ferricyanide Anode Enabling Reversible Na+ Intercalation

“…On the contrary, in the discharging process, both the ions extract from the electrodes. The electrochemical reactions can be described as follows …”