Unidirectional Bias Study Based on Nickel Foam Electrochemical Ion Diode

Abstract

The proposed supercapacitor diode (CAPode) integrates energy storage and diode characteristics into a single device, enabling high-capacity storage for a specific voltage direction. The CAPode expands the functionality of traditional supercapacitors to new technological applications, including microcircuit rectification, logic gate operations, and signal transmission. Conventional active materials for CAPodes include carbon materials and pseudocapacitor materials, among others, which can be complicated and expensive to synthesize. Here, a new commercial nickel foam-based electrochemical ion diode with ultra-high rectification characteristics (rectification ratio I of 5.41 and rectification ratio II of 0.85 at 200 mV s⁻¹) and good charge storage capacity (49.74 C g⁻¹ at 10 mV s⁻¹) is reported. The key to achieving unidirectional charge storage lies in the sieve-selective oxidative reduction of ions in the alkaline electrolyte by nickel foam, enabling unidirectional OH⁻ transport. The emergence of nickel foam electrochemical ion diodes has opened up a new avenue for realizing the design of high-performance CAPodes due to their lower cost and extremely simple preparation process. Furthermore, the device is demonstrated to perform logical operations such as AND and OR in logic gate circuits, and the results presented may facilitate the practical application of ionic diodes.