Space limited growth strategy for ultra-high areal capacity rechargeable aluminum batteries

Increasing the areal loading of the electrodes is the premise to improve the energy density of devices and promote the commercialization of aluminum batteries. However, large areal loading will inevitably increase the amount of aluminum deposition per unit area and aggravate dendritic growth, which seriously affect the safety and stability of devices. In this work, a novel aluminum battery anode is reported, which not only increase the effective active area of the electrode, but also form a stable electrode/electrolyte interface to induce electrodeposition uniformly of aluminum. These traits result from the four advantages of P-Al₂O₃/Al electrode: (1) Homogenizing current density distribution; (2) Redistributing ion concentration gradient; (3) Limiting Al growth in micropores; (4) Large specific surface area provides adequate electrolyte contact. Such an anode retains circulate stably for more than 1400 h at the large area specific capacity of 5 mAh·cm⁻². The protected anode shows also excellent cell stability over 2900 cycles when paired with high current density (10 mA·cm⁻²). In addition, a 480 mAh pouch cell with P-Al₂O₃/Al anode can remain the energy density of 170 Wh·kg⁻¹ and the energy efficiency of 90% (calculated based on the positive active component) under the voltage of 0.5 V to 2.5 V, which means that the amplification of the battery will not reduce the performance of the Al battery. The strategy and method have important practical significance for assembling aluminum batteries with high energy density and high cycle stability.