Self-healing Li–Bi liquid metal battery for grid-scale energy storage

Abstract In an assessment of the performance of a Li|LiCl–LiF|Bi liquid metal battery, increasing the current density from 200 to 1250 mA cm−2 results in a less than 30% loss in specific discharge capacity at 550 °C. The charge and discharge voltage profiles exhibit two distinct regions: one corresponding to a Li–Bi liquid alloy and one corresponding to the two-phase mixture of Li–Bi liquid alloy and the intermetallic solid compound, Li3Bi. Full cell prototypes of 0.1 Ah nameplate capacity have been assembled and cycled at 3 C rate for over a 1000 cycles with only 0.004% capacity fade per cycle. This is tantamount to retention of over 85% of original capacity after 10 years of daily cycling. With minimal changes in design, cells of 44.8 Ah and 134 Ah capacity have been fabricated and cycled at C/3 rate. After a hundred cycles and over a month of testing, no capacity fade is observed. The coulombic efficiency of 99% and energy efficiency of 70% validate the ease of scalability of this battery chemistry. Post mortem cross sections of the cells in various states of charge demonstrate the total reversibility of the Li3Bi solid phase formed at high degrees of lithiation.