Liquid Bi–Sb–Sn\nElectrodes with Synergistic\nStabilization Mechanism for Long-Lifespan Sodium-Based Liquid Metal\nBatteries

Sodium-based liquid metal batteries are well suited for\nstationary\nenergy storage due to their long life, intrinsic safety, and ease\nof scale-up. However, the irreversible alloying reaction between the\npositive current collector (PCC) and the cathodes at high temperatures\nleads to severe capacity degradation of the battery, severely limiting\nits scale-up application. In this work, a Bi–Sb–Sn alloy\ncathode based on a synergistic stabilization mechanism was designed\nfor the first time. Due to the density difference of Bi, Sb, and Sn\nand the compatibility difference of Bi and Sn with the PCC, a part\nof Bi and Sn is spontaneously distributed in the region close to the\nPCC. The protection of Sb is realized by blocking the contact of Sb\nwith the PCC as well as removing the PCC material dissolved in the\ncathode to prevent the loss of active material. Based on such protection,\nthe Na||Bi<sub>36</sub>Sb<sub>24</sub>Sn<sub>40</sub> cell maintained\n99% Coulombic efficiency for 450 cycles at a rate of 0.75 C, with\na capacity retention of 99.56% and a capacity decay rate of 0.001%\nper cycle. In addition, the interaction of Bi, Sb, and Sn during discharge\nalso promotes capacity release and energy efficiency. At 0.3 C, the\nNa||Bi<sub>36</sub>Sb<sub>24</sub>Sn<sub>40</sub> cell achieved 89%\ncapacity utilization and 82% energy efficiency. These results provide\nan idea for the design of other batteries based on liquid metal electrodes.