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, Li 3 Bi. 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 Li 3 Bi solid phase formed at high degrees of lithiation.