Deciphering the Atomic Patterns Leading to MnO2 Polymorphism

Abstract

The mysterious phase transitioning process leading to MnO 2 polymorphism is understood with step-by-step reaction kinetics inside a hydrothermal solution being revealed. A layer-to-tunnel transition mechanism is disclosed at the singleatom resolution. Such transition is driven by the release of intralayer strain generated by the agglomeration of Jahn-Teller active [Mn 3+ O 6 ] octahedra and proceeds via short-range Mn mass transport, leading to the formation of different tunnel phases. Rooted on these fundamental insights, strategies for controlling the synthesis of polymorphic materials are thus provided.

Revealing the Atomic Structures of Exposed Lateral Surfaces for Polymorphic Manganese Dioxide Nanowires

“…It is worth mentioning that the feature of hollow cavities has been commonly seen in hydrothermally synthesized α‐MnO 2 nanowires as previously reported, [ 48–50,34,51 ] and is ascribed to be caused by either an “etching” mechanism [ 49,50 ] or Mn migration‐depletion mechanism by our group. [ 52 ] Yet, no further details regarding the fine structures of the cavities have been reported prior to this work, which, thus, generalizes our finding to be equally important in guiding the facet engineering of such defective features, although they are hidden inside the nanowire.…”

“…It is worth mentioning that although t‐MnO 2 is proposed to possess 3 × 3 tunnels, atomic imaging in Figure 5b–d reveals that in addition to 3 × 3 tunnels, various M × N tunnels ( M and N stand for integral numbers such as 2, 3, 4, and 5) exist. This finding points to the difficulty of precisely controlling the hydrothermal synthesis toward a high degree of phase purity as we discussed previously [ 1,52 ] and thus calls for a more prudent evaluation of the structure–property relationship of t‐MnO 2 for the future work.…”

Hierarchical porosityvialayer-tunnel conversion of macroporous δ-MnO2nanosheet assemblies

“…The process is not spatially uniform, resulting initially in decreased average structural coherence, consistent with STEM observations of others. 65 (4) The PDF data are not severely attenuated as a function of temperature ( Fig. 6), suggesting lateral coherence of the atomic structure is maintained which is consistent with an interlayer condensation mechanism.…”

Understanding the Gap between Academic Research and Industrial Requirements in Rechargeable Zinc‐Ion Batteries

“… a) The theoretically model structure for various crystallographic polymorphs MnO 2 , [39] and monoclinic VO 2 [31c] . Reprinted with permission from Ref.…”

“…Representative RZIB discharge-charge profiles are displayed in Figure 2a, which show typical ion insertion/extraction characteristics. However, unlike the well-established lithiation/delithiation chemistry in a LIB, the RZIB reaction mechanism is still Figure 1. a) The theoretically model structure for various crystallographic polymorphs MnO 2 , [39] and monoclinic VO 2 . [31c] Reprinted with permission from Ref.…”