方铁锰矿Mn_(2)O_(3)作为正极材料的高比容量可充电水性锌离子电池

Bixbyite-Mn_(2)O_(3) as cathode material for rechargeable aqueous Zn ion battery with high specific capacity

由于具有低成本、高安全性、组装简易方便等优点,水性可充电锌离子二次电池被认为是太阳能和风能的最佳储能装置,尤其是锌锰二次电池。目前,锰正极材料的研究较多集中在二氧化锰上,同时,也有关于Mn_(2)O_(3)的研究,但比容量及能量密度皆较低。本文合成了方铁锰矿Mn_(2)O_(3)并将其用于水性锌离子电池的正极材料,在0.2 C倍率下充放时,获得了475 mAh·g^(-1)的高比容量及637 Wh·kg^(-1)的高能量密度。Mn_(2)O_(3)在充放电过程中,具有两个氧化还原峰和两个充放电平台,分别对应H^(+)和Zn^(2+)的脱嵌反应,同时,由于H^(+)较Zn^(2+)半径小,更容易发生脱嵌反应,在大电流密度充放条件下,对容量的贡献率更大;在充电过程中,Mn_(2)O_(3)被逐渐氧化为ε-MnO_(2),+4价锰在放电过程中发生了两电子的转移,从而使其具有高比容量。

Due to the low cost,high safety,and easy assembly,rechargeable aqueous zinc ion batteries are considered the best energy storage device for solar and wind energy,especially rechargeable zinc-manganese batteries.The attention of manganese materials is more focused on manganese dioxide,and there are also some reports about Mn_(2)O_(3),however,the capacity and energy density is low.Herein,bixbyite-Mn_(2)O_(3) was synthesized.When used as the cathode material for zinc ion batteries,it presents a high specific capacity of 475 mAh·g^(-1) and high energy density of 637 Wh·kg^(-1) at 0.2 C.During charged/discharged process,the cycling voltammetry curves display two oxidation-reduction peaks and the charged/discharged curves present two charge-discharge platforms,corresponding to the insertion/extraction of H^(+) and Zn^(2+).Meanwhile,due to the ionic radius of H^(+) is much smaller than Zn^(2+),it has better kinetic performance and easier to embedded in Mn_(2)O_(3),therefore,at high current densities,the H^(+) insertion and deintercalation is the dominate reaction.During the charging process,Mn_(2)O_(3) is gradually oxidized toε-MnO_(2),two-electron Mn^(4+)/Mn^(2+) reactions happen,thus obtaining a high specific capacity.