With dwindling fossil resources and growing environmental concerns, renewable and clean resources, such as wind and solar, are getting more and more attention from the public. Due to the inherent stochastic and unstable characteristic of renewable sources, large-scale energy storage is critical for their grid-connected usage, increasing the capacity and reliability of the future electricity grid.

Recently, many scholars focus on the research of Liquid Metal Battery (LMB), a three-liquid-layer electrochemical cell which is a prospective battery chemistry for large-scale grid-level stationary energy storage. Compared with Lithium-ion batteries, the Li||Sb-Sn LMB exhibits superior rate performance (only 13% capacity loss from 100 mA/cm² to 1 A/cm²), low materials cost (73 $ kW/h), high energy density (200.4 W h/kg) and long cycle life (a fade rate of 0.0078% per cycle) [1]. However, as a developing battery technology, the degradation mechanism of LMBs is not sufficiently studied. To identify the ageing variations of batteries, incremental capacity analysis (ICA) and differential voltage analysis (DVA) are considered to be the two effective in situ techniques [2].

In this work, we recognize ageing variations for LMBs using ICA. The battery used for the test has a nominal capacity of 23 Ah, and voltage operation range is from 0.65 V to 1.2V. A constant current charge-discharge test profile is used to age the battery. After more than 500 charge/discharge cycles, dQ/dV curves are obtained through the voltage data recorded by NEWARE 4000. According to dQ/dV curves, we can easily recognize the ageing variations for LMBs. In addition, a capacity degradation model is established to estimate the State of Health (SOH) of LMBs. Combining with the capacity degradation model, State of Charge estimation and fault diagnosis can be implemented more precisely.

References

[1] Li H, Wang K, Cheng S, et al., High Performance Liquid Metal Battery with Environmentally Friendly Antimony–Tin Positive Electrode[J]. Acs Applied Materials & Interfaces, 2016, 8(20):12830.

[2] Z. Ma, J. Jiang, S. Wei, et al., Investigation of path dependence in commercial lithium-ion cells for pure electric bus applications: aging mechanism identification[J]. J. Power Sources, 2015, 274 (3):29-40.