Graphitic Grain‐Network Nanoarchitecture for Ultrahigh‐Rate and Exceptionally Durable Potassium Ternary Intercalation

ABSTRACT

Potassium–ternary graphite intercalation compounds (K ⁺ ‐T‐GICs) are promising high‐power potassium‐ion storage materials, but their low reversible capacity and poorly understood electrolyte‐dependent behavior have limited their practical viability. Herein, this sensitivity is traced to salt‐dependent electrolyte decomposition that drives resistance growth, blocks K ⁺ diffusion, and induces graphene‐layer exfoliation. Decomposition products accumulate not only at the electrode–electrolyte interface but also deep within the graphite host, where they progressively impede ion transport and trigger structural degradation. Guided by these insights, a disordered grain‐network graphitic nanosheet (DGN‐GNS) architecture is engineered, in which interconnected turbostratic nanograins suppress exfoliation while preserving continuous ion‐transport pathways. The DGN‐GNS electrode delivers a high reversible capacity of ∼165 mA h g ^{− 1} through synergistic K ⁺ storage that couples co‐intercalation with desolvation‐driven intercalation within the porous grain network. Even under ultrafast operation, it sustains ∼80 mA h g ^{− 1} at 30 A g ^{− 1} and retains nearly 100% of its capacity over 10 000 cycles. These metrics represent the highest reversible capacity reported for alkali‐ion–based T‐GICs, and the simultaneous realization of such capacity with ultrahigh‐rate operation and extended cycling stability is unprecedented for K ⁺ ‐T‐GIC anodes, establishing a new benchmark for K ⁺ ‐T‐GIC anodes.