Ultrahigh Areal Capacity Hydrogen‐Ion Batteries with MoO3 Loading Over 90 mg cm−2

High areal capacity electrodes are essential to practical energy storage devices to achieve high volumetric capacity with compacted size. However, high loading of active materials remains a fundamental challenge for most metal-ion batteries (e.g., Li+, Na+, K+) due to sluggish mass transfer kinetics and poor processability. Here, an ultrahigh areal capacity MoO3 electrode based on high loading for hydrogen-ion battery is shown. Hydrogen ions can rapidly intercalate/deintercalate into/from MoO3-nanofibers anode with a high specific capacity of 235 mAh g(-1) at 5 C and superior rate capability up to 200 C at a low loading (approximate to 1 mg cm(-2)). Attributed to the ultrafast H+ diffusion in thick MoO3 electrode, an areal capacity of 22.4 mAh cm(-2) is achieved at the loading over 90.48 mg cm(-2), which is the highest areal capacity ever reported for electrodes of rechargeable batteries, to the best of the authors' knowledge. This study paves the way toward high areal capacity batteries with high-loading active materials.