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

Abstract

Dual‐ion batteries have been developed as a promising technology in recent years, but their high self‐discharge rate leading to low coulombic efficiency (CE) limits their practical applications. This work provides a deft strategy to circumvent this issue by using FeFe(CN)6 as the anode material for hosting Na+ cations, in combination with a graphite cathode for accommodating the bis(trifluoromethanesulfonyl)imide anions (TFSI−). The relatively high bonding force between FeFe(CN)6 and Na+ can hinder self‐extraction of ions from the electrodes, thereby decreasing the self‐discharge rate. The FeFe(CN)6 nanospheres, synthesized by a facile solution reaction method, are well crystallized and dispersed. Na+ insertion into the FeFe(CN)6 cube is determined by cyclic voltammetry (CV), galvanostatic charge–discharge, and X‐ray diffraction tests, suggesting a reversible process. Under a current of 0.05 mA cm−2 the batteries present an acceptable discharge plateau within 1.5–0.7 V and a well‐defined capacity of 75.0 mAh g−1, with a high CE above 98.5% (±0.1%); under 0.2 mA cm−2, cells display a high cyclability of 83.0% capacity retention for 100 cycles, with an excellent CE exceeding 99.6% (±0.1%). Moreover, the batteries exhibit a low self‐discharge rate with a resting capacity decay of 0.32% h−1, outperforming many of the reported dual‐ion cells.

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

“…The self‐discharge effect is a key issue for dual‐ion batteries, which can result in an insufficient C eff . To confirm the self‐discharge process, the battery was charged to 3.9 V at a current of 4 C and then rested for several hours.…”

“…The self-discharge effect is a key issue for dual-ion batteries, which can result in an insufficient C eff . [11][12][13][15][16]24] To confirm the self-discharge process, the battery was charged to 3.9 V at a current of 4 C and then rested for several hours. Figure 6 shows the open-circuit voltage (OCV) vs. time curves of the two EMImTfO-DGBs.…”

Spreading the Landscape of Dual Ion Batteries: from Electrode to Electrolyte

“…As a result, there has been impressive insight into the structure of anode materials for DIBs (Figure 6). [8d,86] According to their mechanisms, they can be classified into four types: (1) intercalation‐type anode materials, such as graphite‐based carbon materials, [87] FePO 4 , [88] Prussian blue [Fe III Fe II (CN) 6 ], [89] Li 4 Ti 5 O 12 , [90] and Na 2 Ti 3 O 7 , [91] where cations are intercalated and de‐intercalated in the anode during charge/discharge; (2) alloy‐type materials, which, upon charge and discharge, produce an alloy with metal ions; (3) conversion‐type anode materials, usually transition metal oxides and disulfides, such as WS 2 , MoS 2 , MoSe 2 , and Co 3 O 4 ; and (4) adsorption‐type materials, which generate a double electric layer during charging and discharging.…”

High Discharge Capacity and Ultra-Fast-Charging Sodium Dual-Ion Battery Based on Insoluble Organic Polymer Anode and Concentrated Electrolyte

“…Currently, the anodes of SDIBs are mainly based on inorganic materials, such as hard carbon, , alloy compounds, , transition metal oxides, , and Prussian blue analogues. , Nevertheless, these materials commonly exhibit poor cyclability, low specific discharge capacity (SDC), and initial Coulomb efficiency (ICE) and more importantly do not conform to the “green battery” development concept . The challenge for green and sustainable SDIB technology is the exploitation of renewable organic anodes, which may eventually be synthesized from biomass. , …”