K‐ion batteries (KIBs) have attracted tremendous attention and seen significant development because of their low price, high operating voltage, and properties similar to those of Li‐ion batteries. In the field of development of full batteries, exploring high‐performing and low‐cost anode materials for K‐ion storage is a crucial challenge. Owing to their excellent cost effectiveness, abundant precursors, and environmental benignancy, hard carbons (HCs) are considered promising anode materials for KIBs. As a result, researchers have devoted much effort to quantify the properties and to understand the underlying mechanisms of HC‐based anodes. In this review, we mainly introduce the electrochemical reaction mechanism of HCs in KIBs, and summarize approaches to further improve the electrochemical performance in HC‐based materials for K‐ion storage. In addition, we also highlight some advanced in situ characterization methods for understanding the evolutionary process underlying the potassiation–depotassiation process, which is essential for the directional electrochemical performance optimization of KIBs. Finally, we raise some challenges in developing smart‐structured HC anode materials for KIBs, and propose rational design principles and perspectives serving as the guidance for the targeted optimization of HC‐based KIBs. image

With theoretical prediction and experimental validation, we propose a novel approach to significantly enhance the conversion efficiency of thermoacoustic (TA) imaging by using an ultrashort microwave pulse. The implementation of the ultrashort microwave pulse leads to orders of magnitude enhancement in excitation efficiency and spatial resolution, compared to that from existing TA imaging techniques. This allows high-resolution ($\sim 100$ micron resolution) TA imaging to be acquired noninvasively. The present work represents a major breakthrough in the conversion efficiency of the TA effect and the resolution of TA imaging, which can potentially be used for clinical imaging.

Bismuth-based perovskites are considered to be promising candidates to substitute the toxic lead-based perovskite in optoelectronics due to their excellent optoelectronic properties, high environmental friendliness, and (moisture, light, and heat) stability. However, there are still few reports about high performance bismuth-based perovskite ultraviolet photodetectors, and is more lacking in ultraviolet imaging demonstration. Herein, we reported a self-powered NiO_x/Cs₃Bi₂Br₉ heterojunction photodetector with excellent photodetection performance by electrochemical depositing NiO_x as the hole transport layer. The optimized NiO_x/Cs₃Bi₂Br₉ heterojunction photodetector exhibits excellent ultraviolet detection performance with a fast response speed of 3.04/4.65 ms, wide linear dynamic range of 116.6 dB, decent responsivity of 4.33 mA·W⁻¹ at 0 V bias, and high detectivity of 1.3 × 10¹¹ jones. The outstanding performance of the optimized NiO_x/Cs₃Bi₂Br₉ heterojunction photodetector is enough to meet the high-quality ultraviolet imaging. Therefore, we further integrated the optimized NiO_x/Cs₃Bi₂Br₉ heterojunction photodetector to the transmission mode ultraviolet multispectral imaging system, achieving admirable imaging results at weak light condition. This work will play a positive role in promoting the development of bismuth-based ultraviolet photodetection and ultraviolet multispectral imaging.

We report the design of a real-time thermoacoustic (TA) scanner dedicated to imaging deep breast tumors and investigate its imaging performance. The TA imaging system is composed of an ultrashort microwave pulse generator and a ring transducer array with 384 elements. By vertically scanning the transducer array that encircles the breast phantom, we achieve real-time, 3D thermoacoustic imaging (TAI) with an imaging speed of 16.7 frames per second. The stability of the microwave energy and its distribution in the cling-skin acoustic coupling cup are measured. The results indicate that there is a nearly uniform electromagnetic field in each XY-imaging plane. Three plastic tubes filled with salt water are imaged dynamically to evaluate the real-time performance of our system, followed by 3D imaging of an excised breast tumor embedded in a breast phantom. Finally, to demonstrate the potential for clinical applications, the excised breast of a ewe embedded with an ex vivo human breast tumor is imaged clearly with a contrast of about 1:2.8. The high imaging speed, large field of view, and 3D imaging performance of our dedicated TAI system provide the potential for clinical routine breast screening.