Confining Aqueous Zn-Br Halide Redox Chemistry by Ti3C2TX MXene.

With fluidity and dangerous corrosiveness, liquid insulating bromine elemental (Br2) can hardly be confined by traditional conductive carriers (mainly carbon materials) for efficient redox without shuttle behavior. Thus, stationary Br2-based energy storage devices are rarely advanced. Here, we introduce an electrochemical active parasite Br2 to the Ti3C2TXMXene host and construct an advanced aqueous zinc redox battery via a facile electrodeposition process (Br-Ti3C2TX). Both ex situ experimental characterizations and density functional theory (DFT) simulations have validated the natural affinity between MXenes and Br species, which is manifested as their spontaneous fixation accompanied by rapid transfer of electrons in the interface region and interlayer confinement. Consequently, the battery delivers a high-voltage plateau at 1.75 V that contributes to an improved energy density of 259 Wh kg-1Br (144 Wh kg-1Br-Ti3C2TX), exhibiting efficient output capability in the high-voltage region. Besides, benefiting from enhanced redox kinetics, the capacity achieved at -15 °C approaches to 69% of the value at room temperature. More importantly, an excellent 10 000 cycles at -15 °C with negligible capacity decay is identified. The paradigm represents a step forward for developing stationary aqueous metal-Br2 batteries.