Engineering Manganese Oxide-Decorated Carbon Stacks with Layered-Inspired Architecture for Lithium-Ion Capacitors

For battery-type electrodes in lithium-ion capacitors (LICs), transitioning from intercalation-type to multi-electron conversion materials offers a promising route to enhance energy density. However, this shift often results in sluggish kinetics and structural instability, limiting practical application. In this work, the layered and channel architectures of intercalation materials are emulated to construct 2D stacked and porous frameworks within conversion-type electrodes, using low-cost MnO as a proof-of-concept example. By further integrating deliberate component engineering-including surface carbonization and heteroatom doping-the resulting electrodes exhibit high reversible capacity and outstanding cycling stability. When coupled with activated carbon in a LIC configuration, the assembled device delivers a high specific power of 12.51 kW kg^-1 while maintaining a specific energy of 287.66 Wh kg^-1. In situ X-ray diffraction and electrochemical analyses reveal a rapid, multi-electron hybrid storage mechanism involving intercalation-conversion reactions and surface adsorption. Crucially, in situ dilatometry and differential electrochemical mass spectrometry, complemented by ex situ characterizations, confirm minimal structural degradation and the early formation of a robust solid electrolyte interphase, which underpins the long-term electrochemical stability.