The Reverse of Electrostatic Interaction Force for Ultrahigh-Energy Al-Ion batteries.

The two-dimensional (2D) MXenes with sufficient interlayer spacing are promising cathode materials for aluminum-ion batteries (AIBs), yet the electrostatic repulsion effect between the surface negative charges and the active anions (AlCl ) hinders the intercalation of AlCl and is usually ignored. Here, we propose a charge regulation strategy for MXene cathodes to overcome this challenge. By doping N and Co, the zeta potential is gradually transformed from negative (Ti C T ) to near-neutral (Ti CNT ), and finally positive (Ti CNT @Co). Therefore, the electrostatic repulsion force can be greatly weakened between Ti CNT and AlCl , or even formed a strong electrostatic attraction between Ti CNT @Co and AlCl , which can not only accommodate more AlCl ions in the Ti CNT @Co interlayers to increase the capacity, but also solve the stacking and expansion problems. As a result, the optimized Al-MXene battery exhibits an ultrahigh capacity of up to 240 mAh g (2-4 times the capacity of graphite cathode, 60-120 mAh g ) and a potential ultrahigh energy density (432 Wh kg , 2-4 times the value of graphite, 110-220 Wh kg ) based on the mass of cathode materials, comparable to LiFePO -based lithium-ion batteries (350-450 Wh kg , based on the mass of LiFePO ).