A Self-Charging Aluminum Battery Enabled by Spontaneous Disproportionation Reaction

Herein, a self-charging mechanism of rechargeable aluminum (Al) batteries with Chevrel phase molybdenum sulfide (Mo 6 S 8 ) cathode is reported. The results unambiguously reveal that the self-charging is a spontaneous disproportionation of Al intercalated Mo 6 S 8 originated from the dynamic shift of Al between occupied sites during Al intercalating and resting. The theoretical study indicates that the fully Al intercalated Mo 6 S 8 in the format of Al 4/3 Mo 6 S 8 is kinetically accessible driven by electrochemical overpotential but thermodynamically unstable due to the repulsion between Al 3+ cations. This mechanism is a true self-charging with no input of any form of energy, thus distinctly superior to the previously reported self-charging mechanisms. Based on this discovery, a semi-flow Al  Mo 6 S 8 battery is designed and demonstrated with long-lasting discharge capability and high capacity.