Nanocrystallites of non-stoichiometric copper sul®des were synthesized via the reaction between [Cu(NH 3 ) 4 ] 2z and thiourea in sealed autoclaves at the low temperature of 60 ³C for 3 h. Thiourea played a key role in the process of Cu 9 S 8 nanocrystal formation. Through adjusting the redox atmosphere, Cu 7 S 4 and CuS were obtained from the freshly formed Cu 9 S 8 nanocrystals. The products were characterized by means of X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), FT-IR spectroscopy and transmission electron microscopy (TEM) techniques. The Cu : S atomic ratios for Cu 9 S 8 and Cu 7 S 4 were 9 : 8.08 and 7 : 4.05, respectively, analyzed by inductively coupled plasma (ICP) spectroscopy. The possible mechanism of phase transformation among copper sul®des (Cu 9 S 8 , CuS, and Cu 7 S 4 ) was discussed. The optical properties of the products were also recorded by means of UV±vis absorption, and photoluminescence spectroscopy.

The rapid development of electric vehicles and modern personal electronic devices is severely hindered by the limited energy and power density of the existing power sources. Here a novel hybrid Zn battery is reported which is composed of a nanostructured transition metal oxide-based positive electrode (i.e., Co O nanosheets grown on carbon cloth) and a Zn foil negative electrode in an aqueous alkaline electrolyte. The hybrid battery configuration successfully combines the unique advantages of a Zn-Co O battery and a Zn-air battery, achieving a high voltage of 1.85 V in the Zn-Co O battery region and a high capacity of 792 mAh g . In addition, the battery shows high stability while maintaining high energy efficiency (higher than 70%) for over 200 cycles and high rate capabilities. Furthermore, the high flexibility of the carbon cloth substrate allows the construction of a flexible battery with a gel electrolyte, demonstrating not only good rechargeability and stability, but also reasonable mechanical deformation without noticeable degradation in performance. This work also provides an inspiring example for further explorations of high-performance hybrid and flexible battery systems.

No abstract

for electron and charge transfer. Therefore, the OV-T n QDs@ PCN/S cathode delivers a superb long-term cycling stability (88% capacity retention over 1000 cycles at 2C) under a S-mass loading of 2.2 mg cm −1 and an E/S ratio of 10 µL mg −1 . In addition, the cathode exhibits good Li + storage at high S-mass loading (4.8 mg cm −1 ) and lean electrolyte (E/S ratio: 4.5 µL mg −1 ), demonstrating its great potential for practical implementation. Our strategy may be extended to other MXenes (e.g., Ti 3 CNT x , Nb 2 CT x , and V 2 CT x ) and pave the way to realize the facile synthesis of QDs with rich OVs for advanced Li-S batteries.

MXenes are promising cathode materials for aqueous zinc-ion batteries (AZIBs) owing to their layered structure, metallic conductivity, and hydrophilicity. However, they suffer from low capacities unless they are subjected to electrochemically induced second phase formation, which is tedious, time-consuming, and uncontrollable. Here we propose a facile one-step surface selenization strategy for realizing advanced MXene-based nanohybrids. Through the selenization process, the surface metal atoms of MXenes are converted to transition metal selenides (TMSes) exhibiting high capacity and excellent structural stability, whereas the inner layers of MXenes are purposely retained. This strategy is applicable to various MXenes, as demonstrated by the successful construction of VSe2@V2CT x , TiSe2@Ti3C2T x , and NbSe2@Nb2CT x . Typically, VSe2@V2CT x delivers high-rate capability (132.7 mA h g–1 at 2.0 A g–1), long-term cyclability (93.1% capacity retention after 600 cycles at 2.0 A g–1), and high capacitive contribution (85.7% at 2.0 mV s–1). Detailed experimental and simulation results reveal that the superior Zn-ion storage is attributed to the engaging integration of V2CT x and VSe2, which not only significantly improves the Zn-ion diffusion coefficient from 4.3 × 10–15 to 3.7 × 10–13 cm2 s–1 but also provides sufficient structural stability for long-term cycling. This study offers a facile approach for the development of high-performance MXene-based materials for advanced aqueous metal-ion batteries.