Initiating a Room‐Temperature Rechargeable Aqueous Fluoride‐Ion Battery with Long Lifespan through a Rational Buffering Phase Design

Abstract

Previously reported fluoride‐ion batteries (FIBs) can only work at high temperatures (>150 °C) with solid electrolytes or organic electrolytes. Aqueous FIB has barely been reported due to the unstable F– electrochemistry in aqueous electrolytes. In addition, the electrode materials commonly suffer from serious and adverse volume expansion during the conversion reaction. Herein, a stable aqueous F– electrochemistry is realized by a rational buffering phase design in which stagger distribution of BiF3 and Bi7F11O5 phases is achieved. The enhanced F– electrochemistry is systematically studied and suggests that the Bi7F11O5 phase plays a vital role in the stability and reversibility of the electrode due to its lower volume change and higher electronic conductivity. Pulverization and dissolution of active species issues are also suppressed. As a result, the assembled battery delivers excellent cycling stability, high reversibility, and superior rate capability, which is far better than conventional solid fluoride shuttle batteries. Mechanism studies demonstrate that the capacity comes from reversible conversion between Bi3+ and Bi0 with an intermediate phase of Bi7F11O5. This work initiates room‐temperature FIBs with aqueous electrolytes and provides a good cycling lifespan, which pave the way to a more practical fluoride ion storage system.

Rate-Determining Process at Electrode/Electrolyte Interfaces for All-Solid-State Fluoride-Ion Batteries

“…Recently, battery systems that utilize multielectron transfer reactions have been demanded for the development of portable devices and hybrid electric vehicles owing to the unsatisfactory energy/power densities of widely applied lithium-ion batteries (LIBs). − However, the multivalent charge carriers of some new battery concepts, for example, Zn 2+ , Mg 2+ , and Al 3+ , undergo much stronger coulombic interactions than monovalent Li ions do; consequently, ion mobility is inferior, leading to lower overall battery power. − Recently, fluoride-ion batteries (FIBs) employing monovalent fluoride anions as charge carriers have been reported frequently; in these batteries, F – is shuttled back and forth due to multielectron transfer reactions, such as two-phase transitions between metals and metal fluorides. − Meanwhile, some tysonite-type, fluorite-type, and PbF 2 -based compounds and their derivatives, such as La 1– x Ba x F 3– x , Pb 2– x Sn x F 4 , and BaSnF 4 , are known as fast F-ion conductors with relatively high ionic conductivities. ,− Aqueous FIBs that exhibit ultrahigh fluoride-ion conductivity (∼10 –2 to 10 –1 S cm –1 ) have also been fabricated in a latest report, for which the future development is highly expected . However, in the current stage, it is greatly challengeable to achieve a high energy density in aqueous systems compared with all-solid-state systems due to problems such as dissolution of active materials, narrow electrochemical windows, and so forth.…”

“…13,16−25 Aqueous FIBs that exhibit ultrahigh fluoride-ion conductivity (∼10 −2 to 10 −1 S cm −1 ) have also been fabricated in a latest report, for which the future development is highly expected. 26 However, in the current stage, it is greatly challengeable to achieve a high energy density in aqueous systems compared with all-solid-state systems due to problems such as dissolution of active materials, narrow electrochemical windows, and so forth. Therefore, allsolid-state FIBs have been regarded as promising alternatives with high energy/power densities and favorable battery kinetics.…”

Silk Fibroin Coating Enables Dendrite‐free Zinc Anode for Long‐Life Aqueous Zinc‐Ion Batteries

“…Fortunately, the use of rechargeable batteries can overcome the instability of alternative energy. [3] Rechargeable batteries can easily store these intermittent energies and then output electricity steadily when needed. [4][5][6] With the advantages of high energy density and working voltage, lithium-ion batteries (LIBs) dominate most of the secondary battery market.…”

Relieving hydrogen evolution and anodic corrosion of aqueous aluminum batteries with hybrid electrolytes

“…One of the hypotheses is that bulky CF 3 SO 3 − anions can reduce the number of dissociative water molecules and weaken the hydrogen evolution reaction (HER). Inspired by the above-mentioned works and progresses in the aqueous energy storage systems, 23,24 highly concentrated electrolytes are promising for AAIBs with decent efficiency. Unfortunately, the price of Al(OTF) 3 is super high (near 10 USD per gram, from Acros) and other common Al salts present relatively low solubilities in water.…”