Hierarchical hollow MnTe2/CoTe2 composite nanospheres assembled from porous nanosheets: Synergistic structural engineering for high-performance hybrid supercapacitors

Abstract

Achieving high energy density, high power density, and long-term durability in hybrid supercapacitors demands electrode materials designed to overcome intrinsic performance compromises. To address this need, we report the first synthesis of hierarchical hollow MnTe2/CoTe2 composite nanospheres assembled from interconnected porous nanosheets as an advanced battery-type electrode. Our novel two-step methodology is pivotal: first, we develop a unique solvothermal route to fabricate solid Mn-Co layered double hydroxide (LDH) spheres with a distinctive architecture composed of densely intergrown nanosheets. This bespoke precursor then undergoes a self-templating, morphology-preserving tellurization, simultaneously hollowing the core via the Kirkendall effect and converting the solid MnCo-LDH spheres assembled from dense nanosheets into a conductive MnTe2/CoTe2 composite comprising two distinct crystalline phases. The resulting architecture synergistically combines an electrolyte-reservoir hollow core, shortened ion-diffusion paths through the porous nanosheets, and the high conductivity and rich redox activity of this bimetallic telluride composite. Consequently, the optimized hollow MnTe2/CoTe2 composite synthesized at 500 °C (denoted as MCT-500) delivers a high specific capacity of 1354 C g-1 at 1 A g-1 (representing a ~79% enhancement over the MnCo-LDH precursor, which delivers 755 C g-1), while maintaining excellent rate capability (68.25% retention at 40 A g-1, significantly outperforming the precursor's 49% retention) and exhibiting remarkable cycling stability (89.2% capacity retention after 10,000 cycles vs. 53.5% for MnCo-LDH). When configured into a practical AC//MCT-500 hybrid device, it achieves a high energy density of 64.88 Wh kg-1 at 811 W kg-1 and retains 43.97 Wh kg-1 at an ultrahigh power density of 32.1 kW kg-1, positioning it among the best-reported systems and surpassing recently reported bimetallic tellurides, selenides, and sulfides. This work thus addresses the critical challenge of distinguishing true architectural novelty from mere compositional replication in the design of high-performance telluride electrodes. This work establishes a new and superior member in the family of telluride-based electrodes and provides a generalizable synthesis blueprint where innovation in precursor design directly enables breakthrough electrochemical performance.