Regulating Graphitic Microcrystalline and Single-Atom Chemistry in Hard Carbon Enables High-Performance Potassium Storage

Hard carbon (HC) has attracted considerable research interest as the most promising anode for potassium-ion batteries (PIBs) due to its tunable interlayer spacing and abundant voids to accommodate K+. However, the practical application of hard carbon is severely hampered by low initial Coulombic efficiency (ICE) and high plateau potential. Herein, a manganese ion-catalyzed pyrolysis strategy is explored to regulate the graphitic microcrystalline structure and localized electron distribution in hard carbon that greatly improve K+ plateau storage and ICE. Systematic experimental measurements, in situ/ex situ observations, dynamic analysis, and density functional theory calculations elucidate that the introduction of Mn2+ ions could catalyze the formation of short-ordered graphitic nanodomains in hard carbon to provide abundant insertions of K+, and meanwhile induce localized electron distribution through the MnN3C coordination structure to enable dynamic K+ diffusion and electron transfer kinetics. Consequently, the modulated hard carbon exhibits a high low-potential-plateau capacity, excellent rate capability, and high initial Coulombic efficiency in potassium half-cell configurations. More importantly, the charge storage mechanism of "adsorption-intercalation" is proposed based on the correlation between carbon structures and discharge/charge plateau. This work provides an in-depth insight into the fundamentals of microstructure regulation of hard carbon anode for high-performance PIBs. A manganese ion-catalyzed pyrolysis strategy is explored to regulate the graphitic microcrystalline structure and localized electron distribution in hard carbon that greatly improve K+ plateau storage and initial Coulombic efficiency (ICE). The as-prepared hard carbon anode possesses high low-potential-plateau capacity, excellent rate capability, and high ICE for potassium ion half-cells, as well as high energy/power density for potassium-ion hybrid capacitors.image