Rechargeable zinc–manganese dioxide batteries that use mild aqueous electrolytes are attracting extensive attention due to high energy density and environmental friendliness. Unfortunately, manganese dioxide suffers from substantial phase changes (e.g., from initial α-, β-, or γ-phase to a layered structure and subsequent structural collapse) during cycling, leading to very poor stability at high charge/discharge depth. Herein, cyclability is improved by the design of a polyaniline-intercalated layered manganese dioxide, in which the polymer-strengthened layered structure and nanoscale size of manganese dioxide serves to eliminate phase changes and facilitate charge storage. Accordingly, an unprecedented stability of 200 cycles with at a high capacity of 280 mA h g−1 (i.e., 90% utilization of the theoretical capacity of manganese dioxide) is achieved, as well as a long-term stability of 5000 cycles at a  utilization of 40%. The encouraging performance sheds light on the design of advanced cathodes for aqueous zinc-ion batteries.

Portable and multifunctional electronic devices are developing in the trend of being small, flexible, roll‐up, and even wearable, which asks us to develop flexible and micro‐sized energy conversion/storage devices. Here, the high performance of a flexible, wire‐shaped, and solid‐state micro‐supercapacitor, which is prepared by twisting a Ni(OH)2‐nanowire fiber‐electrode and an ordered mesoporous carbon fiber‐electrode together with a polymer electrolyte, is demonstrated. This micro‐supercapacitor displays a high specific capacitance of 6.67 mF cm–1 (or 35.67 mF cm–2) and a high specific energy density of 0.01 mWh cm–2 (or 2.16 mWh cm–3), which are about 10–100 times higher than previous reports. Furthermore, its capacitance retention is 70% over 10 000 cycles, indicating perfect cyclic ability. Two wire‐shaped micro‐supercapacitors (0.6 mm in diameter, ≈3 cm in length) in series can successfully operate a red light‐emitting‐diode, indicating promising practical application. Furthermore, synchrotron radiation X‐ray computed microtomo­graphy technology is employed to investigate inner structure of the micro‐device, confirming its solid‐state characteristic. This micro‐supercapacitor may bring new design opportunities of device configuration for energy‐storage devices in the future wearable electronic area.

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We report the electrochemical properties of layered lithium-rich Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 cathode materials with various degrees of stacking faults, which are prepared via a facile molten-salt method using a variety of fluxes including KCl, Li 2 CO 3 , and LiNO 3 . The frequency of the stacking faults is highly dependent on the temperature and molten salt type used during the synthesis. A well-crystallized Li 1.18 Mn 0.54 Ni 0.13 Co 0.13 O 2 nanomaterial with a larger amount of stacking faults synthesized at 800 C for 10 h in an inactive KCl flux delivers a high reversible capacity of $310 mA h g À1 at room temperature, while the samples prepared in the chemically active fluxes with a smaller amount of stacking faults show poor electrochemical performance. Broader contextAdvanced lithium-ion batteries (LIBs) that deliver more energy at rapid charge and discharge rates are essential for on-board storage technology in hybrid electric vehicles (HEVs) or electric vehicles (EVs). High energy density lithium-rich transition metal oxide cathodes represent an important milestone in materials design for advanced lithium-ion batteries due to their high reversible capacities of $250 mA h g À1 at low cost. Although much progress has been achieved on the lithium-rich transition-metal oxides, the relationship between the microstructure e.g. stacking faults and electrochemical properties of lithiumrich transition-metal oxides remains unclear. In this study, we report the electrochemical performance of Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 electrodes with various degrees of stacking faults and reveal that structural defects in the crystal structure of the Li 2 MnO 3 component play a key role in the electrochemistry of xLi 2 MnO 3 $(1 À x)LiMO 2 electrodes using powder X-ray diffraction (XRD), selected area electron diffraction (SAED), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The results reported herein provide new insights into the design and synthesis of advanced electrode materials with various degrees of structural defects for use in high-performance energy storage and conversion devices.

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