Carbon host pore structure regulation boosting fast and stable Se-K electrochemistry towards Se-K ion capacitors

Abstract

The selenium (Se) electrochemistry plays a critical role in developing new generation electrochemical energy storage systems beyond the ever-dominating lithium based era. However, fast kinetics and stable Se electrochemistry still remain great challenges, particularly involving K+ reaction instead of Li+. Herein, we report a facile carbon host using pore structure regulation strategy, in which the abundant micropores provide large specific surface area and pore volume that can physically confine and accommodate the small molecular Se. These micropores not only boost the fast reaction kinetics of small molecular Se with K+, but also can restrain the shuttle effect of polyselenides effectively during the reversible reaction. The ordered and interconnected macropores and mesopores can offer rapid mass transfer channels, together with the chemical adsorption from the N-doping, synergistically improving the charger transfer efficiency and reversible stability. The Se/nitrogen-doped macro-/meso-/microporous carbon (Se@NM3C) delivers large specific capacity of 728 mA h g−1 (0.05C), remarkable rate performance, and superior cycling stability. A novel potassium ion (K-ion) capacitors based on this Se–K electrochemistry (Se–KICs) can achieve high energy/power densities and great long-term service life (86% after 10,000 cycles at 2 A g−1). This work unveils insights into chalcogen based electrochemistry for high performance electrochemical energy storage systems.