Ultra-fast charging in aluminum-ion batteries: electric double layers on active anode

With the rapid iteration of portable electronics and electric vehicles, developing high-capacity batteries with ultra-fast charging capability has become a holy grail. Here we report rechargeable aluminum-ion batteries capable of reaching a high specific capacity of 200 mAh g −1 . When liquid metal is further used to lower the energy barrier from the anode, fastest charging rate of 10 4 C (duration of 0.35 s to reach a full capacity) and 500% more specific capacity under high-rate conditions are achieved. Phase boundaries from the active anode are believed to encourage a high-flux charge transfer through the electric double layers. As a result, cationic layers inside the electric double layers responded with a swift change in molecular conformation, but anionic layers adopted a polymer-like configuration to facilitate the change in composition. Developing high-capacity batteries with high-rate performance has been a challenge. Here, the authors use a liquid metal alloy as anode in the aluminum-ion battery to push the boundaries, enabling the discovery of new roles of electric double layers in facilitating a high-rate charge transfer.