Novel high-voltage cathode for aqueous zinc ion batteries:Porous K_(0.5)VOPO_(4)·1.5H_(2)O with reversible solid-solution intercalation and conversion storage mechanism

Cathode materials that possess high output voltage,as well as those that can be mass-produced using facile techniques,are crucial for the advancement of aqueous zinc-ion battery(ZIBs)applications,Herein,we present for the first time a new porous K_(0.5)VOPO_(4)·1.5H_(2)O polyanionic cathode(P-KIVP)with high output voltage(above 1.2 V)that can be manufactured at room temperature using straightforward coprecipitation and etching techniques.The P-KVP cathode experiences anisotropic crystal plane expansion via a sequential solid-solution intercalation and phase co nversion pathway throughout the Zn^(2+)storage process,as confirmed by in-situ synchrotron X-ray diffraction and ex-situ X-ray photoelectron spectroscopy.Similar to other layered vanadium-based polyanionic materials,the P-KVP cathode experiences a progressive decline in voltage during the cycle,which is demonstrated to be caused by the irreversible conversion into amorphous VO_(x).By introducing a new electrolyte containing Zn(OTF)_(2) to a mixed triethyl phosphate and water solution,it is possible to impede this irreversible conversion and obtain a high output voltage and longer cycle life by forming a P-rich cathode electrolyte interface layer.As a proof-of-concept,the flexible fiber-shaped ZIBs based on modified electrolyte woven into a fabric watch band can power an electronic watch,highlighting the application potential of P-KVP cathode.

Direct Growth of Graphene on Silicon by Metal-Free Chemical Vapor Deposition

The metal-free synthesis of graphene on singlecrystal silicon substrates, the most common commercial semiconductor, is of paramount significance for many technological applications. In this work, we report the growth of graphene directly on an upside-down placed,single-crystal silicon substrate using metal-free, ambientpressure chemical vapor deposition. By controlling the growth temperature, in-plane propagation, edge-propagation, and core-propagation, the process of graphene growth on silicon can be identified. This process produces atomically flat monolayer or bilayer graphene domains, concave bilayer graphene domains, and bulging few-layer graphene domains. This work would be a significant step toward the synthesis of large-area and layer-controlled, high-quality graphene on single-crystal silicon substrates.

Unveiling the mechanism of charge compensation in Li_(2)Ru_(x)Mn_(1-x)O_(3)by tracking atomic structural evolution

The relationship between the structural evolution and redox of Li-rich transition-metal layered oxides(LLOs)cathodes remains ambiguous,obstructing the development of high-performance lithium-ion(Li^(+))battery.Herein,the coherent effects of local atomic and electronic structure in Li_(2)Ru_(x)Mn_(1-x)O_(3)(LRMO)with a wide voltage window(1.3–4.8 V)is identified by in situ X-ray absorption fine spectroscopy(XAFS)and chemometrics.We not only skillfully separated the redox active structures to track the electrochemical path,but also visualized the coupling mechanism between the evolution of Ru-Ru dimer and the(de)excitation of cations and anions.Furthermore,introducing manganese triggers the“heterogeneity”of coordination environment and electronic structure between Ru and Mn after discharge to 3 V.The change of thermodynamic and kinetic paths affects the relithiation,and further leads to the hysteresis of the anion activation structure relaxation of Li_(2)Ru_(0.4)Mn_(0.6)O_(3)relative to Li_(2)RuO_(3)(LRO).Additionally,it is demonstrated that the high charge cut-off voltage restrains the relaxation of anionic active structure in LRO from a new perspective through comparative experiments.Our work associates the evolution of atomic structure with charge compensation and negative electrochemical reactions such as voltage hysteresis(VH)and capacity attenuation,deepening the understanding electrochemical reaction mechanism of LLOs during the first cycle and providing a theoretical support for the further design and synthesis of high-efficiency cathodes.