Achieving a smart thermal management for lithium-ion batteries by electrically-controlled crystallization of supercooled calcium chloride hexahydrate solution

The discharge performance of lithium-ion batteries (LIBs) is severely degraded at low temperatures. The existing LIBs preheating systems face challenges including high costs and consumption of battery capacity. Therefore, this paper developed an innovative electrically-controlled crystallization electrode based on calcium chloride hexahydrate (CCH) (ECE-CCH) by melting-solidification method and devised an electrically-controlled phase change material (PCM) preheating system based on CCH (EPS-CCH) for LIBs. The stable supercooling and great heat storage/release properties of the CCH, as well as the excellent low-voltage electrically-controlled crystallization performance of ECE-CCH, enable EPS-CCH to achieve safe and controllable thermal management of LIBs at the optimal operating temperature. Under the premise of maintaining the stable supercooling and heat storage properties of CCH (50.67 wt% CaCl2 solution), 48 wt% CaCl2 solution was selected as the heat storage material (melting point: 31.5 °C, latent heat: 153.0 J/g). The ECE-CCH could release the latent heat of the supercooled CCH solution in <5 s at low DC voltages (1.0–2.0 V). 100-cycle experiments illustrated that ECE-CCH had good cycle stability and an optimal operating voltage range of 1.0–1.5 V. Finally, EPS-CCH was designed to achieve on-demand control of thermal management of LIBs at low temperatures. Compared to LIBs without EPS-CCH at 5 °C, LIBs with EPS-CCH exhibited a significantly increased discharge capacity of 14.27%, 11.35%, and 7.04% at discharge rates of 0.5C, 1.0C, and 1.5C, respectively. The research findings of the ECE-CCH and the EPS-CCH would promote the development of LIBs preheating technologies.