Enabling stable MnO2 matrix for aqueous zinc-ion battery cathodes
Enabling stable MnO2 matrix for aqueous zinc-ion battery cathodes
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DOI：
10.1039/d0ta08638j
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发表时间：
2020-11-14
影响因子：
11.9
通讯作者：
Parkin, Ivan P.
中科院分区：
文献类型：
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作者：
Jiao, Yiding;Kang, Liqun;Parkin, Ivan P.
水基锌离子电池正极材料MnO2面临的首要问题是在循环过程中会发生结构变化，导致容量输出不稳定。将紧密结合的离子预先嵌入到MnO2结构中被证明是解决这一问题的有效方法。然而，预嵌插的机制仍不清楚。在本论文中，用不同量的预嵌K+制备了两种不同的β-MnO2(K0.28MnO2中心点0.1H(2)O和K0.21MnO2中心点0.1H(2)O)，并将其应用于AZIBs的阴极。所制备的K0.28MnO2中心点0.1H(-1)O正极具有较高的比容量(100 mA g(-1)下300 mA h g(-1))、满意的倍率性能(5A g(-1)下容量恢复率35%)和良好的循环性能(在2Ag(-1)下1000次循环后容量保持率约为95%)，而K0.21MnO2中心点0.1H(-1)O的循环性能和倍率性能较差。通过可逆沉积Zn4SO4(OH)(6)中心点5H(2)O(ZSH)，离子在电极间迁移，同时发生了Mn价态的跃迁。这项工作首次通过密度泛函理论模拟系统地揭示了预嵌插离子的作用，结果表明，在K/Mn比约为0.26的阈值以上，K离子通过稳定三角洲相来抑制结构转变。为了展示其商业潜力，采用高负载活性材料的AZIB被制造出来，与大多数商业设备相比，它提供了足够的能量和功率密度。
The primary issue faced by MnO2 cathode materials for aqueous Zn-ion batteries (AZIBs) is the occurrence of structural transformations during cycling, resulting in unstable capacity output. Pre-intercalating closely bonded ions into the MnO2 structures has been demonstrated as an effective approach to combat this. However, mechanisms of the pre-intercalation remain unclear. Herein, two distinct delta-MnO2 (K0.28MnO2 center dot 0.1H(2)O and K0.21MnO2 center dot 0.1H(2)O) are prepared with varying amounts of pre-intercalated K+ and applied as cathodes for AZIBs. The as-prepared K0.28MnO2 center dot 0.1H(2)O cathodes exhibit relatively high specific capacity (300 mA h g(-1) at 100 mA g(-1)), satisfactory rate performance (35% capacity recovery at 5 A g(-1)) and competent cyclability (ca. 95% capacity retention after 1000 cycles at 2 A g(-1)), while inferior cyclability and rate performance are observed in K0.21MnO2 center dot 0.1H(2)O. A stable delta-MnO2 phase is observed upon cycling, with the reversible deposition of Zn4SO4(OH)(6)center dot 5H(2)O (ZSH), ion migration between electrodes and synchronous transition of Mn valence states. This work firstly and systematically reveals the role of the pre-intercalated ions via density functional theory simulations and show that above a threshold K/Mn ratio of ca. 0.26, the K ions suppress structural transformations by stabilizing the delta phase. To demonstrate its commercial potential, AZIBs with high-loading active materials are fabricated, which deliver adequate energy and power densities compared with most commercial devices.