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

Abstract 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 4 − ) hinders the intercalation of AlCl 4 − 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 3 C 2 T x ) to near‐neutral (Ti 3 CNT x ), and finally positive (Ti 3 CNT x @Co). Therefore, the electrostatic repulsion force can be greatly weakened between Ti 3 CNT x and AlCl 4 − , or even formed a strong electrostatic attraction between Ti 3 CNT x @Co and AlCl 4 − , which can not only accommodate more AlCl 4 − ions in the Ti 3 CNT x @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 −1 (2–4 times the capacity of graphite cathode, 60–120 mAh g −1 ) and a potential ultrahigh energy density (432 Wh kg −1 , 2–4 times the value of graphite, 110–220 Wh kg −1 ) based on the mass of cathode materials, comparable to LiFePO 4 ‐based lithium‐ion batteries (350–450 Wh kg −1 , based on the mass of LiFePO 4 ).