An ultrahigh pyridinic N-content-doped porous carbon monolith is reported, and the content of pyridinic N reaches up to 10.1% in overall material (53.4 ± 0.9% out of 18.9 ± 0.4% N content), being higher than most of previously reported N-doping carbonaceous materials, which exhibit greatly improved electrochemical performance for potassium storage, especially in term of the high reversible capacity. Remarkably, the pyridinic N-doped porous carbon monolith (PNCM) electrode exhibits high initial charge capacity of 487 mAh g at a current density of 20 mA g , which is one of the highest reversible capacities among all carbonaceous anodes for K-ion batteries. Moreover, the K-ion full cell is successfully assembled, demonstrating a high practical energy density of 153.5 Wh kg . These results make PNCM promising for practical application in energy storage devices and encourage more investigations on a similar potassium storage system.

Sodium-ion battery (SIB) is especially attractive in cost-effective energy storage device as an alternative to lithium-ion battery. Particularly, metal phosphides as potential anodes for SIBs have recently been demonstrated owing to their higher specifi c capacities compared with those of carbonaceous materials. Unfortunately, most reported metal phosphides consist of irregular particles ranged from several hundreds nanometers to tens of micrometers, thus delivering limited cyclic stability. This paper reports the sodium storage properties of additive-free Cu 3 P nanowire (CPNW) anode directly grown on copper current collector via an in situ growth followed by phosphidation method. Therefore, as a result of its structure features, CPNW anode demonstrates highly stable cycling ability with an ≈70% retention in capacity at the 260th cycle, whereas most reported metal phosphides have limited cycle numbers ranged between 30 and 150. Besides, the reaction mechanism between Cu 3 P and Na is investigated by examining the intermediate products at different charge/discharge stages using ex situ X-ray diffraction measurements. Furthermore, to explore the practical application of CPNW anode, a pouch-type Na + full cell consisting of CPNW anode and Na 3 V 2 (PO 4 ) 3 cathode is assembled and characterized. As a demonstration, a 10 cm × 10 cm light-emmiting diode (LED) screen is successfully powered by the Na + full cell. Figure 6. a) Schematic representation of the pouch-type CPNW/NVP Na + full cell. b) Cycling performance of the CPNW/NVP Na + full cell at current densities of 600 mA g −1 . c,d) Optical images showing a fl exible LED screen powered by the pouch-type CPNW/NVP Na + full cell. wileyonlinelibrary.com

Carbon‐based materials are considered to be one of the most promising materials for negative electrodes of the future, because of their good chemical stability, high electrical conductivity, and environmental benignity. However, to date, the underlying principles of K‐ion storage in carbonaceous anodes remain elusive, which greatly hinders the development of such a category of anodes. Herein, the ultrastable K‐ion storage of carbonaceous anode through systematic analyses, including comprehensive electrochemical characterizations, kinetics calculations, and structural/compositional evolution mechanism studies, is theoretically elucidated and experimentally verified. Specifically, it is found that the uniquely envelope‐like nitrogen‐doped carbon nanosheets with high pseudocapacitive could bring ultrastable storage of potassium ions, delivering a high initial reversible capacity of 367 mAh g−1 at a current density of 50 mA g−1 and retain 70.5 and 75.6% at current densities of 500 and 1000 mA g−1 after 1000th cycle, respectively. This study could enlighten researchers on further progress in the field of carbonaceous K‐ion battery negative electrode with a long cycle life.

Owing to the lower cost and easy accessibility of potassium, potassium‐ion batteries are considered as potential substitutes for lithium‐ion batteries. A porous carbon monolith with ultrahigh pyridinic N content is successfully synthesized by Yu Chen, Chenglin Yan, and co‐workers in article https://doi.org/10.1002/adma.201702268, which exhibits excellent electrochemical performance, especially in terms of reversible capacity, for both K+ half‐cells and full‐cells.

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