Abstract

Manganese dioxide (MnO₂) is promising cathode materials for aqueous rechargeable zinc ion batteries (ARZIBs) owing to their diverse polymorphy, high operating voltage and environmental benignity. However, the sluggish electrochemical kinetics and poor cycling stability are major issues to binder their practical applications. Herein, potassium pre-intercalated manganese dioxide (KMO) nanoflakes were fabricated via simple hydrothermal method. The KMO nanoflakes are assigned to be layered birnessite phase with layer spacing of 7.2 Å and the atomic ratio between K and Mn is around 1:3. As cathode for ARZIBs, the KMO electrode delivered specific capacity of 252 mAh g⁻¹ at current density of 0.1 A g⁻¹ and gained specific capacity of 288 mAh g⁻¹ after 100 cycles, being with the retention of 114%. The KMO cathode displayed outstanding cycling stability that under large current density of 2.0 A g⁻¹ it could retain 84.3% of initial capacity after 4000 cycles. By analyzing the electrochemical dynamics and phase evolution of KMO electrode during discharge/charge process, it was validated that the potassium pre-intercalation in MnO₂ framework not only provides enlarged spacing for Zn²⁺/H⁺ ion transferring but also is served as strong support to stabilize the layer structure, resulting in high energy density and better cycling stability. Our work provides rational way for designing high-performance manganese-based cathode materials for ARZIBs.

Graphical abstract

摘要

二氧化锰 (MnO ₂ ) 因其多样的多晶型、高工作电压和环境友好性而成为水系可充电锌离子电池 (ARZIB) 的有前途的阴极材料。然而，缓慢的电化学动力学和较差的循环稳定性是限制其实际应用的主要问题。在此，通过简单的水热法制备钾预插二氧化锰 (KMO) 纳米薄片。KMO 纳米薄片被指定为层状水钠锰矿相，层间距为 7.2 Å，K 和 Mn 之间的原子比约为 1:3。作为 ARZIB 的阴极，KMO 电极在 0.1 A g ^-1的电流密度下提供 252 mAh g ^-1的比容量，并获得 288 mAh g ^{-1的比容量}100次循环后，保留率为114%。^{KMO 正极显示出出色的循环稳定性，在 2.0 A g -1}的大电流密度下，它可以在 4000 次循环后保持初始容量的 84.3%。通过分析KMO电极在放电/充电过程中的电化学动力学和相演化，验证了MnO ₂骨架中钾的预嵌入不仅为Zn ²⁺ /H ⁺离子转移提供了更大的空间，而且还起到了很强的作用。支持稳定层结构，从而获得高能量密度和更好的循环稳定性。我们的工作为设计用于 ARZIB 的高性能锰基正极材料提供了合理的方法。

图形概要