A Micro Battery Supercapacitor Hybrid Device with Ultrahigh Cycle Lifespan and Power Density Enabled by Bi‐Functional Coating Design

Abstract Micro energy storage devices (MESDs) have emerged as promising energy providers for micro applications due to their integrated performance. However, the limited cycle life and low power density of microbattery, and low energy density of microsupercapacitor have consistently impeded their broader practical implementation. Herein, to obtain a MESD with a long cycle life, excellent power density, and superior energy density, a novel micro battery‐supercapacitor hybrid (MBSH) device is fabricated. Two types of 3D microelectrodes are fabricated, namely, a nanowire network anode based on PEDOT‐TiON and a porous cathode based on Ni(OH)₂. Benefiting from the unique hydrophobic characteristics of the PEDOT layer, high electrical conductivity of TiON, and high conductivity, and abundant ion diffusion channels of network microstructure, PEDOT‐TiON NW microelectrodes demonstrate exceptional cycling stability by retaining 70% of their capacity after 40 000 cycles. The achieved MBSH exhibits an extended voltage window ranging from 0 to 1.9 V, impressive power density of 77.5 mW cm⁻², and a superior energy density of 55.6 µWh cm⁻². Furthermore, it maintains a remarkable capacity retention rate of 71.6% even after undergoing 30 000 cycles. This innovative design paves the way for the developing of high‐performance microdevices with superior electrochemical properties.