Revealing Exceptional Supercapacitive‐Storage Performance: Atomic‐Level Insight Into Cu‐Incorporation Activated Amorphous CoNi Hydroxide

Nickel‐cobalt‐based hydroxides have established their niche in stationary storage applications where high theoretical capacitance, affordability, and carbon footprint matter most. Nonetheless, realizing their high rate capability and enduring cycling stability are challenged, originating from sluggish electron transfer and inadequate mechanical strength. Here, we pioneered to leverage on atomically uniform Cu‐incorporation via light illumination to optimize the electronic and atomic structure of amorphous CoNi hydroxide. Remarkably, the as‐fabricated amorphous CuCoNi hydroxide electrode embraces an ultra‐high rate capacity of 74.1% following a 50‐fold increase of current density and an unprecedented cycling life (∼ 92.6% of the initial capacitance retention after 100 000 cycles at 10 mA cm −2 ), far exceeding performances reported in the literature. The exceptional electrochemical performance could be attributed to Cu introduction, which leads to the transfer of more electrons from Ni to Co during the energy storage process, facilitating Ni in achieving the tetravalent state and obtaining additional pseudocapacitance. Additionally, the Cu‐incorporation could effectively induce the appearance of defect states and lower the adsorption energy of OH − , thus expediting surface redox reactions. This atomic structure tuning strategy may shed light on the electrode material design for high‐performance energy storage devices.