A general method for constructing robust, flexible and freestanding MXene@metal anodes for high-performance potassium-ion batteries

Metal-based anode materials such as Sb, Sn, Bi, etc., attract great attention for battery use due to their high electronic conductivity and high energy density. However, the large volume expansion during the alloying-dealloying process results in fast performance decay. In this work, we successfully grow hierarchical Sb, Sn and Bi firmly on MXene paper via a facile one-step electrodeposition process in a green ethylene glycol-based system. As robust, flexible, free-standing and binder-free anodes for potassium-ion batteries, the hierarchical structure provides a short diffusion distance for potassium ions and buffer volume change during the potassiation/depotassiation process. Highly conductive and flexible MXene paper serves as an elastic current collector providing an electronic highway to facilitate electron transport and accommodate volume change during the cycling process. MXene@Sb delivers a high reversible capacity of 516.8 mA h g(-1), a high rate capacity of 270 mA h g(-1) at 500 mA g(-1), and stable capacity retention with a capacity fading rate of only 0.042% per cycle. This work may also be interesting in relation to research on other rechargeable batteries, catalysts, sensors, etc.