Shan Xiaoqiang, Guo Fenghua, Charles Daniel S, Lebens-Higgins Zachary, Abdel Razek Sara, Wu Jinpeng, Xu Wenqian, Yang Wanli, Page Katharine L, Neuefeind Joerg C, Feygenson Mikhail, Piper Louis F J, Teng Xiaowei
Department of Chemical Engineering, University of New Hampshire, Durham, NH, 03824, USA.
Department of Physics, Applied Physics and Astronomy, Binghamton University, Binghamton, NY, 13902, USA.
Nat Commun. 2019 Oct 31;10(1):4975. doi: 10.1038/s41467-019-12939-3.
Birnessite is a low-cost and environmentally friendly layered material for aqueous electrochemical energy storage; however, its storage capacity is poor due to its narrow potential window in aqueous electrolyte and low redox activity. Herein we report a sodium rich disordered birnessite (NaMnO) for aqueous sodium-ion electrochemical storage with a much-enhanced capacity and cycling life (83 mAh g after 5000 cycles in full-cell). Neutron total scattering and in situ X-ray diffraction measurements show that both structural water and the Na-rich disordered structure contribute to the improved electrochemical performance of current cathode material. Particularly, the co-deintercalation of the hydrated water and sodium-ion during the high potential charging process results in the shrinkage of interlayer distance and thus stabilizes the layered structure. Our results provide a genuine insight into how structural disordering and structural water improve sodium-ion storage in a layered electrode and open up an exciting direction for improving aqueous batteries.
水钠锰矿是一种用于水性电化学储能的低成本且环境友好的层状材料；然而，由于其在水性电解质中的电位窗口狭窄且氧化还原活性低，其存储容量较差。在此，我们报道了一种用于水性钠离子电化学存储的富钠无序水钠锰矿（NaMnO），其容量和循环寿命得到了显著提高（全电池中5000次循环后为83 mAh g）。中子全散射和原位X射线衍射测量表明，结构水和富钠无序结构都有助于当前阴极材料电化学性能的改善。特别地，在高电位充电过程中，水合水和钠离子的共脱嵌导致层间距收缩，从而稳定了层状结构。我们的结果为结构无序和结构水如何改善层状电极中的钠离子存储提供了真实的见解，并为改进水性电池开辟了一个令人兴奋的方向。
