A high-performance intermediate-temperature aluminum-ion battery based on molten salt electrolyte

Non-aqueous rechargeable aluminum-ion batteries (AIBs) are a promising candidate for grid-scale energy storage due to their high theoretical energy density, safety, environmental benignity, and the abundance of Al sources. However, the limited cathode capacity and the high price of ionic liquid electrolytes hinder their large-scale applications. Herein, an intermediate-temperature AIB composed of nickel disulfide-based cathode and NaCl-AlCl3-Al2S3 molten salt electrolyte is reported. A highly reversible conversion mechanism between Ni3S4 and Ni during cycling is proved with cathode capacities exceeding 500 mAh g−1. The full cell delivers a cathode capacity of 320 mAh g−1 at 240 °C and a current density of 2000 mA g−1 with negligible capacity fade after 2000 cycles. The raw material cost is estimated to be as low as 28 $ kWh−1 based on the electrode and electrolyte materials. The molten salt electrolyte-based AIB provides promising opportunities to build energy storage systems with low cost, high safety, stable electrochemical performance, and long lifetime.