V‐Induced Low‐Spin State Mn ³⁺ Suppresses Jahn–Teller Distortion for High‐Performance Aqueous Zinc Ion Batteries

Abstract

Abstract The Jahn–Teller distortion caused by high‐spin state Mn 3+ (t 2g 3 e g 1 ) is a major limiting factor for improving both the specific capacity and cycling stability of MnO 2 cathodes in aqueous zinc‐ion batteries. Thus, an intrinsic strategy for optimizing MnO 2 involves the effective elimination of the high‐spin state Mn 3+ (t 2g 3 e g 1 ) during electrochemical process. Herein, we focus on structural design that constructed NH 4 V 3 O 8 ‐coated MnO 2 (Mn@V) nanorods to achieve the low‐spin state of Mn 3+ (t 2g 4 e g 0 ) and inhibit the Jahn–Teller distortion. The well‐designed Mn@V cathode exhibits outstanding specific capacity (513.5 mAh g −1 at 0.2 A g −1 ), remarkable rate performance (205 mAh g −1 at 2.0 A g −1 ), and excellent cycling stability (201 mAh g −1 after 2000 cycles at 1.0 A g −1 ). Through a series of advanced characterization techniques, such as ex‐situ X‐ray absorption spectroscopy, combined with theoretical calculations, we systematically demonstrate that the NH 4 V 3 O 8 coating layer alters electron configuration through the V–O–Mn bridge bonds and induces the low‐spin state Mn 3+ (t 2g 4 e g 0 ) in MnO 2 , thereby suppressing the Jahn–Teller distortion and enhancing cycling stability. This study offers profound insights into the inhibition of the Jahn–Teller distortion from an electron spin perspective, and presents a facile approach to synergistically enhance specific capacity and cycling stability.