Clean electricity such as solar energy and wind energy has developed rapidly in recent years, but stability still needs to be improved. Moreover, the current global distribution of power resources is very uneven. If we want to get rid of fossil fuels, we must add key energy storage links to the existing power system, so that power can be more rationally redistributed in space and time, while meeting high capacity, high security, low cost and so on. However, the existing smart grid battery system needs to overcome the problems of energy storage cost and life, so as to meet the application requirements of power storage. The liquid lithium metal battery system has low energy storage cost and long service life, and has broad application prospects in the field of small and medium-sized distributed energy storage, but it generally has the following two problems: 1) due to the high melting point of lithium metal, the battery operating temperature is generally above 450°C, which makes a high operating costs; 2) dissolution of lithium in the molten salt leads to self-discharge and lower coulombic efficiency.

In order to solve these problems, the researchers assembled two model batteries Li||LLZTO||Sn–Pb and Li||LLZTO||Bi–Pb with molten lithium metal as the negative electrode, molten Sn-Pb or Bi-Pb alloy as the positive electrode, and garnet-type Li6.4La3Zr1.4Ta0.6O12 (LLZTO) solid electrolyte ceramic tube. The electrolyte encapsulates the molten lithium metal in a tubular form to conduct lithium ion conduction while isolating the liquid metal electrode. At the same time, a liquid-solid interface is formed in the battery system instead of the liquid-liquid interface, which greatly reduces the interface impedance.

Studies have shown that the assembled Li||LLZTO||Sn-Pb and Li||LLZTO||Bi-Pb batteries can be stably cycled for about one month at a current density of 50~100 mAcm−2 and 240°C, and show excellent power capacity and coulombic efficiency. The high-capacity, high-safety and low-cost solid-state electrolyte liquid lithium metal battery brings new enlightenment to the further development of large-scale energy storage systems.

Reference

[1] Yang Jin, Kai Liu, Hui Wu, Yi Cui, et al. An intermediate temperature garnet-typesolid electrolyte-based molten lithium battery for grid energy storage. NatureEnergy 2018. https://www.nature.com/articles/s41560-018-0198-9.