Reverse Dual‐Ion Battery by Coupling Adsorption and Conversion Mechanism

Abstract

and TFSI − ) intercalation, DIBs and RDIBs deliver a high working voltage and consequently a considerable energy density. However, they normally possess unsatisfactory power density because of the sluggish dynamics of large anion intercalation or alloying. Capacitive materials based on surface adsorption or shallow redox reactions are capable of providing a much higher power density. [13][14][15][16] Therefore, replacing intercalation or alloy-type electrodes with at least one adsorption-type material is regarded as an effective way to break through the trade-off of power and energy density. [17] Although the intercalation of anions can bring high voltage, it also results in some adverse issues. The reaction in high voltage holds out harsh requirements to the electrolyte, that is, high voltage may lead to decomposition of the electrolyte. As a consequence, it is needed to develop a kind of cathode that can work at a lower voltage. However, in order to ensure high energy density, it is necessary to increase the specific capacity of the cathode materials. As to the anode, the conversion reactions between metallic Li and lithium halides have been demonstrated to show high capacity and good reversibility with low voltage. By using such conversion reactions, several kinds of halide ion batteries have been developed, including chloride ion batteries, in our recent work. [18][19][20][21] If two electrodes based on adsorption and conversion mechanism can be coupled in one DIB, it would be expectable to construct a rechargeable battery with simultaneously high energy density and power density.Herein, mesoporous vanadium-doped anatase (VTO) synthesized by hydrothermal method and lithium metal is used as cathode and anode, along with a non-lithium electrolyte to assemble an RDIB, respectively. The charge storage of the cathode is based on adsorption/desorption of electrolyte cations, whereas a conversion reaction happens on the anode side, which is totally different from the existing (R)DIBs (Figure 1). The VTO/Li RDIB shows a high capacity of 123.8 mAh g −1 at 200 mA g −1 after 500 cycles. More significantly, it provides a high power density of 1532 W kg −1 along with a considerable energy density of 214 Wh kg −1 at 1 A g −1 . The effective coupling of adsorption and conversion reaction mechanism induces an optimization of the power/energy density of DIBs, providing a new design strategy for high-performance energy storage systems.As one kind of promising energy storage device, dual-ion batteries (DIBs) have attracted extensive attention because of their high voltage, environmental friendliness, and low cost. However, they generally suffer from low power density resulting from sluggish kinetic of electrolyte anion intercalation. In this work, a new strategy to break through the trade-off of power density and energy density in DIBs is proposed. A vanadium-doped anatase is synthesized by the hydrothermal method and used as the cathode of DIB (employing Li as the anode). During the charging/discharging process, the organic ca...