Sulfide synergistic electrochemical activity for high-performance alkaline rechargeable microbatteries

Alkaline rechargeable microbatteries have attracted considerable and sustained attention in recent years. However, the complicated fabrication process and the limited specific capacitance of electrodes are still key problems for the development of microbatteries. Herein, we develop a simple approach to enhance electrochemical activity of electrodes via rational design of material components. A sulfide synergistic bimetallic electrode composed of Ni-Co layered double hydroxides (NiCo-LDHs) and Co₄S₃ composites (NiCo-LDHs-S) is prepared by one-step electrodeposition. Thanks to the richer redox couples in NiCo-LDHs-S and high conductivity of Co₄S₃, the areal capacitance of NiCo-LDHs-S cathode is ~ 5.8 times, ~ 19.7 times and 1.5 times as high as that of electrodes based on cobalt sulfur composites (Co-O-S), nickel sulfur composites (Ni-O-S) and NiCo-LDHs, respectively. A carbon-modified Fe₃O₄ (Fe₃O₄@C) anode is prepared to promote electron transfer, leading to an areal capacitance of 207.2 mC cm⁻² at a current density of 2 mA cm⁻². An efficient alkaline rechargeable microbattery using NiCo-LDHs-S as a cathode and Fe₃O₄@C as an anode is obtained and shows an areal capacitance of 61.7 mC cm⁻² and an energy density of 16.4 μWh cm⁻² (1.0 mW cm⁻²).