Strengthening ion uptake and mitigating volume change via bimetallic telluride heterojunction for ultrastable K-ion hybrid capacitors

Unitary transition-metal tellurides are appealing to supersede their oxide and sulfide congeners in the realm of K -ion storage because of advanced electrical conductivity. Nevertheless, the marked volume expansion of tellurides during K+ uptake/release giving rise to rapid capacity decay remains a daunting obstacle. Distinct from the previously reported singular telluride configurations, bimetallic heterojunction comprising Mo-Co telluride moiety and dual-carbon encapsulation is developed in this study to endow durable K-ion storage. Density functional theory calculations unlock the synergistic effects of bimetallic Mo-Co tellurides with respect to aug-menting electrical conductivity and favoring K-ion adsorption. In situ transmission electron microscopy analysis clearly reveal the structural evolution of bimetallic Mo-Co telluride during a discharge/charge cycle, showing a mitigated volume expansion rate of 2.37 %. Accordingly, the heterojunction exhibits excellent cycling stability (160 mAh/g for 2000 cycles at 1.0 A/g) and favorable capacity output (322 mAh/g at 0.2 A/g), outperforming unitary MoTe2 or CoTe2 counterparts. Thus-derived K-ion hybrid capacitor full-cell manifests elongated lifespan over 6000 cycles at 1.0 A/g. This telluride heterojunction material might offer a valuable reference to rendering high-performance potassium-based energy storage devices.

Automated summary

In this study, a bimetallic heterojunction structure of transition-metal tellurides was developed, showing superior electrical conductivity and stable potassium ion storage performance. The synergistic effects and structural evolution of bimetallic tellurides were revealed through density functional theory calculations and in situ transmission electron microscopy analysis. The heterojunction exhibited excellent cycling stability and favorable capacity output, outperforming unitary metal tellurides. Therefore, this research is of great significance for high-performance potassium-based energy storage devices.