Sb-Cu alloy cathode with a novel lithiation mechanism of ternary intermetallic formation: Enabling high energy density and superior rate capability of liquid metal battery

Antimony (Sb) is an attractive cathode for liquid metal batteries (LMBs) because of its high theoretical voltage and low cost. The main obstacles associated with the Sb-based cathodes are unsatisfactory energy density and poor rate-capability. Herein, we propose a novel Sb64Cu36 cathode that effectively tackles these issues. The Sb64Cu36 (melting point: 525 degrees C) cathode presents a novel lithiation mechanism involv-ing sequentially the generation of Li2CuSb, the formation of Li3Sb, and the conversion reaction of Li2CuSb to Li3Sb and Cu. The generated intermetallic compounds show a unique microstructure of the upper floated Li2CuSb layer and the below cross-linked structure with interpenetrated Li2CuSb and Li3Sb phases. Compared with Li3Sb, the lower Li migration energy barrier (0.188 eV) of Li2CuSb significantly facilitates the lithium diffusion across the intermediate compounds and accelerates the reaction kinetics. Consequently, the Li||Sb64Cu36 cell delivers a more excellent electrochemical performance (energy den-sity: 353 W h kg-1 at 0.4 A cm-2; rate capability: 0.59 Vat 2.0 A cm-2), and a much lower energy storage cost of only 38.45 $ kW h-1 than other previously reported Sb-based LMBs. This work provides a novel cathode design concept for the development of high-performance LMBs in applications for large-scale energy storage.(c) 2022 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.