Toward Deterministic 3D Energy Storage Electrode Architectures via Electrodeposition of Molybdenum Oxide onto CNT Foams

Three-dimensional (3D) deterministic design of electrodes could enable simultaneous high energy and power density for electrochemical energy storage devices. The goal of such electrode architectures is to provide adequate charge (electron and ion) transport pathways for high power, while maintaining high active material loading (>10 mg cm^–2) for high areal and volumetric capacities. However, it remains a challenge to fabricate such electrodes with processes that are both scalable and reproducible. Toward this end, here, we demonstrate how the fabrication of such an electrode is made possible by combining tunable, free-standing, and aligned carbon nanotube (CNT) foams with aqueous electrodeposition of a model intercalation-type transition metal oxide, MoO₃. Morphological characterization including X-ray microcomputed tomography indicates that the obtained composite is homogeneous. Electrodes with an active mass loading of up to 18 mg cm^–2 reached near-theoretical Li-ion intercalation capacities within 1.7 h. The highest-mass loading electrodes also led to areal and volumetric capacities of 4.5 mA h cm^–2 and 290 mA h cm^–3, respectively, with 55% capacity retention for charge/discharge times of 10 min. Overall, this work demonstrates a scalable, deterministic 3D electrode design strategy using electrodeposition and free-standing, aligned CNT foams that lead to high areal and volumetric capacities and good rate performance due to well-distributed charge transport pathways.