Unveiling a Hidden Conversion Pathway in CoSe2 Anodes via Rationally Designed CNT-Interwoven Hollow Carbon Microclusters for High-Performance Potassium-Ion Batteries

초록

The search for sustainable energy storage has positioned potassium-ion batteries (PIBs) as a compelling alternative to lithium-ion systems, yet the lack of robust anode materials remains a significant hurdle. Transition-metal selenides, particularly CoSe2, are attractive for their high theoretical capacity and fast kinetics, but they inevitably succumb to catastrophic structural failure. This degradation is rooted in the traditional stepwise insertion pathway (CoSe2 → KxCoSe2 → Co + K2Se), which triggers a relentless lattice expansion exceeding 250%. Herein, we report the rational design of CNT-interwoven hollow carbon microclusters as a rigid nanoconfined host to modulate this reaction behavior. This specific architecture does more than buffer volume changes; it fundamentally steers the electrochemical behavior toward a previously hidden conversion-insertion mechanism mediated by a Co3Se4 intermediate. Thermodynamic analysis via first-principles calculations confirms that this newly unearthed route effectively sequesters major strain during the initial CoSe2 → Co3Se4 transition, thereby preserving the electrode's integrity throughout subsequent potassiation. In situ X-ray diffraction provides direct, real-time evidence of this stabilized Co3Se4 phase and its smooth evolution into KxCo3Se4, bypassing the destructive traditional landscape. Our findings underscore that meticulous structural tailoring can be a powerful tool to capture elusive intermediates and redefine reaction pathways for high-endurance PIB anodes. © 2026 The Author(s). Advanced Science published by Wiley-VCH GmbH.

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