The limited resources and uneven distribution of lithium stimulate strong motivation to develop new rechargeable batteries that use alternative charge carriers. Potassium-ion batteries (PIBs) are at the top of the list of alternatives because of the abundant raw materials and relatively high energy density, fast ion transport kinetics in the electrolyte, and low cost. However, several challenges still hinder the development of PIBs, such as low reversible capacity, poor rate performance, and inferior cycling stability. Research on the cathode is currently focused on developing materials with high energy density and cycling stability, mainly including layered transition metal oxides, polyanion compounds, organic compounds, etc. Anodes based on intercalation reactions, conversion reactions, and alloying with potassium are currently under development, and promising results have been published. This review comprehensively summarizes the research effort to date on the electrode material optimization (e.g., crystals, morphology, reaction mechanisms, and interface control), the synthesis methods, and the full cell fabrication for PIBs to enhance the electrochemical potassium storage and provide a platform for further development in this battery system.

Transparent conducting oxides constitute a unique class of materials combining properties of electrical conductivity and optical transparency in a single material. They are needed for a wide range of applications including solar cells, flat panel displays, touch screens, light emitting diodes and transparent electronics. Most of the commercially available TCOs are n -type, such as Sn doped In ₂ O ₃ , Al doped ZnO, and F doped SnO ₂ . However, the development of efficient p -type TCOs remains an outstanding challenge. This challenge is thought to be due to the localized nature of the O 2 p derived valence band which leads to difficulty in introducing shallow acceptors and large hole effective masses. In 1997 Hosono and co-workers (1997 Nature 389 939) proposed the concept of ‘chemical modulation of the valence band’ to mitigate this problem using hybridization of O 2 p orbitals with close-shell Cu 3 d ¹⁰ orbitals. This work has sparked tremendous interest in designing p -TCO materials together with deep understanding the underlying materials physics. In this article, we will provide a comprehensive review on traditional and recently emergent p -TCOs, including Cu ⁺ -based delafossites, layered oxychalcogenides, nd ⁶ spinel oxides, Cr ³⁺ -based oxides (3 d ³ ) and post-transition metal oxides with lone pair state ( ns ² ). We will focus our discussions on the basic materials physics of these materials in terms of electronic structures, doping and defect properties for p -type conductivity and optical properties. Device applications based on p -TCOs for transparent p – n junctions will also be briefly discussed.

This paper presents a novel method and rationale for utilizing carbonized MOFs for sulphur loading to fabricate cathode structures for lithium–sulphur batteries. Unique carbon materials with differing hierarchical pore structures were synthesized from four types of zinc-containing metal–organic frameworks (MOFs). It is found that cathode materials made from MOFs-derived carbons with higher mesopore (2–50 nm) volumes exhibit increased initial discharge capacities, whereas carbons with higher micropore (<2 nm) volumes lead to cathode materials with better cycle stability.