Ordered Macroporous MoS2-Carbon Composite with Fast and Robust Sodium Storage Properties to Solve the Issue of Kinetics Mismatch of Sodium-Ion Capacitors

Abstract

Metal-ion capacitors (including Li+, Na+, and K+) effectively combine a battery negative electrode capable of reversibly intercalating metal cations, together with an electrical double-layer positive electrode. However, such novel cell design has a birth defect, namely kinetics mismatch between sluggish negative electrode and fast positive electrode, thus limiting the energy-power performance. Herein, we design a MoS2-carbon composite anode with the ordered macroporous architecture and interlayer-expanded feature, exhibiting the fast and reversible Na+ redox processes. This kinetically favored anode is coupled with a homemade activated carbon cathode that allows for the excellent electrochemical performance of sodium-ion capacitor with respect to large specific capacity, high-rate capability, and robust cycling. Through quantification of the potential swings of anode and cathode via a three-electrode Swagelok cell, we for the first time observe the abnormal variation law of potential swings and thus directly providing the evidence that the kinetics gap has been filled up by this kinetically favored anode. Our results represent a crucial step toward understanding the key issues of kinetics mismatch for hybrid cell, thus propelling the development of design of kinetically favored anode materials for high-performance metal-ion capacitors.