Semi‐Solid Na‐K Alloy Anode with Enhanced Stabilities for Advanced Sodium‐Ion Batteries

Abstract Sodium‐potassium (Na‐K) alloys are recognized as a promising anode material due to their unique liquid properties at room temperature, which endow them with self‐healing ability and dendrite‐free potential. However, the liquid nature of Na‐K alloys also introduces significant instability, which undermines their inherent advantages and thus restricts their practical application. In this work, a semi‐solid Na‐K anode consisting of a homogeneous mixture of solid and liquid phases is developed, aiming to enhance stability while preserving the original benefits. The synergistic interaction between the solid and liquid phases enables the semi‐solid Na‐K anode to integrate the advantages of both solid and liquid anodes, thereby demonstrating excellent comprehensive performance. Notably, when matched with NaClO 4 electrolyte, the formation of a solid electrolyte interphase containing KClO 4 crystal layers is observed, which possesses a high modulus to inhibit dendrite growth and promote uniform deposition. As a result, full cells utilizing the semi‐solid Na‐K anode achieve a capacity retention of 89.18% after 1000 cycles at 1 C, while also demonstrating excellent rate performance, with a high capacity of 93 mAh g⁻ 1 at 20 C. This work expands the application potential of Na‐K alloy anodes and provides a constructive approach for the high‐performance Na metal anodes.